The problem of modeling atherosclerosis. Experimental atherosclerosis Results and discussion
Owners of patent RU 2500041:
The invention relates to experimental medicine, pathophysiology and concerns the modeling of atherosclerosis, which can be used to study the diagnosis, prevention and treatment of this disease. For this purpose, laboratory animals - rats are fed with cholesterol powder in the amount of 1%, margarine 10%, Mercazolil 10 mg/kg and vitamin D - 2.5 IU per kg of body weight. Additionally, the animals undergo an operation consisting of ligating the renal pedicle of the left kidney with non-absorbable suture material and suturing the upper pole of the right kidney, leaving 2/3 of the organ. The method is easy to implement, does not cause death in animals, and is an adequate model of endothelial damage and the development of the atherosclerotic process. 12 ill., 4 tab., 1 pr.
The invention relates to experimental medicine, pathophysiology, and can be used for the purposes of diagnosis, prevention and treatment of the atherosclerotic process.
Atherosclerosis and its complications continue to lead in the structure of morbidity and mortality in Western countries and Russia. Mortality from cardiovascular pathologies in the world is twice as high as from cancer, and 10 times higher than from accidents [Vorobeva E.N., Schumacher G.I., Osipova I.V. and others//Cardiovascular therapy and prevention. - 2006, No. 5 (6). - P.129-136; Lupach N.M., Khludeeva E.A., Lukyanov P.A. and others // Russian Medical Journal. - 2010, No. 4. pp.71-74; Titov V.N. // Clinical laboratory diagnostics. 2006, No. 4. P.310].
One of the main risk factors (RFs) for the development of atherosclerosis is a disorder of lipid metabolism in the body. Dyslipidemia, consisting of a decrease in α-high-density lipoproteins (HDL), with an increase in β-lipoproteins, or low-density lipoproteins (LDL), pre-β lipoproteins, or very low-density lipoproteins (VLDL), contributes to the development of atherosclerosis. Moreover, modified, most often subjected to peroxidation, oxidized (oxy-LPN) have atherogenic properties. They help increase the synthesis of caveolin-1, which leads to a decrease in the formation of NO by the endothelium [Vorobeva E.N., Schumacher G.I., Osipova I.V. and others // Cardiovascular therapy and prevention. - 2006, No. 5 (6). - P.129-136; Zotova I.V., Zateyshchikov D.A., Sidorenko B.A. // Cardiology. - 2002, No. 4. - P.57-67; Titov V.N. // Clinical laboratory diagnostics. 2006, No. 4. P.310]. Oxidized lipoproteins are active irritants for monocytes, which penetrate into the subendothelial space, turning into macrophages, and then, as modified LDL accumulates in them, into foam cells. Activated macrophages and foam cells release biologically active substances - growth factors, anti-inflammatory cytokines, cell adhesion molecules, which promote platelet aggregation, vasoconstriction and adhesion of leukocytes, and consequently, the development of the inflammatory process in the arterial wall and the progression of atherosclerosis. Also, hydroxy-LDL induces the proliferation of vascular smooth muscle cells (SMCs), while HDL, on the contrary, carries out the reverse transport of cholesterol (C) from the vascular wall and macrophages to the liver [Titov V.N. // Clinical laboratory diagnostics. 2006, No. 4. P.310].
Arterial hypertension (AH) is the second important risk factor for the development of atherosclerosis. It has been proven that drug control of blood pressure in hypertensive patients reduces the risk of strokes by 40%, myocardial infarction by 8%, and overall mortality from heart disease by 10% [Chicherina E.N., Milyutina O.V. // Clinical medicine. 2009. - No. 2. - P.18-21]. With isolated hypertension in men aged 47.5±8.4 years, lipid spectrum indicators shift towards an increase in total cholesterol (TC), triglycerides (TG), LDL cholesterol, a decrease in HDL cholesterol, an increase in the atherogenic coefficient (AA) [Ovchinnikova L K., Yagudina R.I., Ovchinnikova E.A. // Russian pharmacies. - 2007. - No. 14. - P.26-31]. Hypertension contributes to an increase in endothelial permeability and accumulation of lipoproteins in the intima [Shlyakhto E.V., Gavrisheva N.A., Ovchinnikova O.A. and others. The influence of induced inflammation on collagen metabolism in atherosclerotic plaques in mice // Medical Immunology. 2008, No. 6. P.507-512]. It has been proven that the reason for the activation of protein and lipid peroxidation (PO) in rats with spontaneous hypertension is the increased production of oxygen radicals and the ineffectiveness of endogenous systems for their inactivation. It is also known that the development of spontaneous hypertension in rats is accompanied by a systemic inflammatory response syndrome: its initial stage is the activation (priming) of polymorphonuclear leukocytes (neutrophils), increased production and secretion of active forms of O 2 - and H 2 O 2 by them and intensification of protein production and at the same time fatty acids (FA). The reaction of O 2 - with nitric oxide (NO) forms ONOO- and deprives NO of its biological effect as a relaxation factor. A decrease in NO leads to an increase in blood pressure according to the development of a vicious circle [Zotova I.V., Zateyshchikov D.A., Sidorenko B.A. // Cardiology. - 2002, No. 4. - P.57-67].
From a modern point of view, a key link in the pathogenesis of atherosclerosis is considered to be endothelial dysfunction (ED), which is an imbalance between the main functions of the endothelium: vasodilation and vasoconstriction, inhibition and promotion of proliferation, antithrombotic and prothrombotic, antioxidant and pro-oxidative [Lupach N.M., Khludeeva E.A. ., Lukyanov P.A. and others // Russian Medical Journal. - 2010, No. 4. pp.71-74; Allison B. Reiss, Amy D. // Journal of investigative medicine. 2006. Vol.54, N. 3. P.123-131; Huber S.A., Sakkinen P., David S. // Circulation. 2001. - N. 103. - P. 2610-2616]. Nitric oxide is an important regulator in the cardiovascular system, a messenger that mediates auto- and paracrine effects. In the body, the NO synthesis reaction is catalyzed by the NO synthase (NOS) family. NOS use L-arginine as a substrate and NADPH diaphorase as a cofactor. NADPH diaphorase is involved in the transport of electrons to the prosthetic group of the enzyme. The determination of NADPH diaphorase is based on the formation of diformazan in the presence of endogenous β-NADPH and tetrazolium salts [Zotova I.V., Zateyshchikov D.A., Sidorenko B.A. // Cardiology. 2002, No. 4. P.57-67; Shumatova T.A., Prikhodchenko N.G., Grigoryan L.A. and others //Pacific Medical Journal. 2010, No. 3. P.59-61; Allison B. Reiss, Amy D. Glass // Journal of investigative medicine. 2006. Vol.54, N. 3. P.123-131].
Data from clinical and epidemiological studies have proven the pathogenetic influence of hypertension and hyperlipidemia on the vascular wall, but the period of formation of ED under the combined action of these factors under experimental conditions has not been clearly established [Ovchinnikova L.K., Yagudina R.I., Ovchinnikova E.A. // Russian pharmacies. - 2007. - No. 14. - P.26-31; Vorobyova E.N., Schumacher G.I., Osipova I.V., Khoreva M.A. and others // Cardiovascular therapy and prevention. - 2006. - No. 5(6). - 129-136; Nagornev V.A., Voskayants A.N. // Vestn. RAMS, 2006. - No. 9-10. P.66-74; Davignon J. Ganz P. //Circulation. - 2004; 109: 27-32].
Animal models play an important role in the study of diseases, including atherosclerosis. Rats are often used in modeling hyperlipidemia as a risk factor for atherosclerosis [Meshcherskaya K.A., Borodina G.P., Koroleva N.P. On the methodology for selecting agents that affect cholesterol metabolism. // Eleutherococcus and other adaptogens from Far Eastern plants. / Ed. K.A. Meshcherskaya. - Vladivostok, 1966. - P.289-294; Sannikova A.A., N.N. Chuchkova, Gaisina E.Sh. Immunomodulatory effect of glucosaminylmuramyl dipeptide in altered lipid metabolism and atherosclerosis. // Bulletin of the Ural Medical Economic Science. - 2008. - No. 1. - P.64-66. 10; Yudina T.P., Charevach E.I., Tsybulko E.I., Maslennikova E.V., Plaksen N.V. The hypolipidemic effect of a complex emulsifier containing laminal algae and an aqueous extract from the roots of the soapwort Sa ponaria officinalis L., in an experiment on rats. // Questions of nutrition. - 2008. - T. 77, No. 2. - P.76-79]. Their acquisition and maintenance are relatively inexpensive, the animals are easy to handle and reproduce well in captivity. Of all experimental animals, rats have the best studied metabolism [Kulikov V.A., Chirkin A.A. Features of lipoprotein metabolism in rats // Pathological physiology and experimental therapy. - 2004. - No. 1. - P.26-27].
However, the above researchers only assessed changes in blood lipid composition over a short period of observation (from 16 days to 3 months); the models lack data on morphological and functional changes in the vessel wall; the inclusion of long-term compensatory mechanisms that prevent the formation of vascular lesions is not taken into account.
There are known methods for modeling atherosclerosis (clause RU No. 2033646; class G09B 23/28, 1995; clause RU No. 2327228, class G09B 23/28, 2008, bulletin No. 17; clause RU No. 2127113, class A61K 31 /70, A61K 31/505, 1999).
However, the above methods involve the administration of medications (obsidan - 1 mg per 100 g of body weight, hydrocortisone acetate suspension - 1.5 mg per 100 g of animal weight, uridine at a dose of 50 mg per 1 kg of body weight once a day for 6-8 days) against the background of a diet enriched with fats, artificially change the animal’s metabolism and inadequately reflect the formation of natural pathogenetic mechanisms that play a key role in the development of atherosclerosis.
The prototype is the modeling of hyperlipidemia in rats over a long period of time [Kropotov A.V. The influence of cohosh and marigold on some indicators of lipid metabolism and the reproductive system (experimental study). Author's abstract. dissertation for the scientific degree of candidate of medicine. Sciences, Vladivostok - 1975, p.5]. The well-known method gives the diet pronounced atherogenic properties. The rats are kept on a high fat diet for 7 months. Cholesterol powder in the amount of 1%, margarine 10%, Mercazolil 10 mg/kg and vitamin D in the amount of 2.5 IU per kg of body weight of the rat are added to the animal feed.
However, the prototype did not evaluate changes in the functional and morphological properties of the vascular endothelium; the researchers observed only changes in the lipid spectrum in the blood and liver biopsies of rats.
Taking into account the peculiarities of the metabolic processes of rats, which contribute to the formation of their resistance to fat load, the authors of the invention used a combination of hyperlipidemia with arterial hypertension for the most pronounced damage to the endothelium. The method enhances the disruption of cholesterol metabolism processes, the formation of persistent signs of atherosclerotic vascular damage, taking into account the inclusion of urgent and long-term compensatory mechanisms.
The objective of the claimed invention is to develop an experimental model of endothelial dysfunction based on studying the combined effect of hyperlipidemia and arterial hypertension on the morphological structure of blood vessels in rats.
The objective of the proposed method is achieved by combining feeding laboratory animals with an atherogenic diet, consisting of adding cholesterol powder in the amount of 1%, 10% margarine, 10 mg/kg Mercazolil, and vitamin D - 2.5 IU per kg body weight of the rat, and performing an operation that includes ligating the renal pedicle of the left kidney with non-absorbable suture material and suturing the upper pole of the right kidney, leaving 2/3 of the organ, which contributes to the development of persistent renovascular arterial hypertension. During the experiment, the following steps were completed:
Monitoring of the state of lipid metabolism in blood serum was carried out during isolated experimental hyperlipidemia (EG) and under the complex influence of an atherogenic diet and arterial hypertension (D+AH).
Monitoring blood pressure levels in EG and D+AG models.
Determination of NADPH diaphorase activity in the endothelium of the aorta, femoral arteries and microvessels of the anterior abdominal wall (AW) in two experimental models.
Assessment of the state of the lumen of blood vessels in experimental animals using computer magnetic resonance imaging (MRI).
The technical result of the proposed method is to obtain persistent structural disorders of the vascular wall, in comparison with an isolated atherogenic diet, in order to create a model of atherosclerosis in laboratory animals for the diagnosis, prevention and treatment of atherosclerosis.
The essence of the claimed invention is the combination of hyperlipedemia and renovascular hypertension in laboratory rats.
Hyperlipidemia was achieved by adding cholesterol powder in the amount of 1%, 10% margarine, 10 mg/kg Mercazolil and vitamin D - 2.5 IU per kg body weight of the rat.
Renovascular hypertension was performed by ligating the renal pedicle of the left kidney with non-absorbable suture material and suturing the upper pole of the right kidney (leaving 2/3 of the organ).
This technique makes it possible to obtain persistent structural damage to the vascular wall, compared with isolated experimental hyperlipidemia.
The essence of the proposed method is illustrated by drawings, where Fig. 1a-1c shows an increase in the width of the common carotid artery, brachiocephalic trunk and thoracic aorta in experimental rats, respectively, at the 2nd month of the study; Fig. 2 shows the definition in the D+AG model uneven contrasting of the arteries, which suggests local atherogenic changes in the arterial wall, Fig. 3 - in the aorta of experimental rats, staining with hematoxylin and eosin shows changes in the architectonics of elastic fibers, displacement of myocyte nuclei to the periphery, their compaction, cellular infiltration of the wall, thickening of the endothelium, Increase × 400 (A×Cam MRc camera, Germany), hematoxylin and eosin staining, in Fig. 4 perinuclear optically empty formations are visualized, magnification ×400 (A×Cam MRc camera, Germany), hematoxylin and eosin staining; figure 5 - hematoxylin and eosin staining of the aorta (control), magnification × 100 (A×Cam MRc camera, Germany), hematoxylin and eosin staining; in Fig.6, perinuclear optically empty formations are visualized in the femoral arteries, magnification × 400, Hematoxylin and eosin staining; Fig. 7 - hematoxylin and eosin staining of the femoral artery (control), magnification × 400 (A×Cam MRc camera, Germany) hematoxylin and eosin staining; Fig. 8 - in the group of rats with D+AH, when the aorta was stained with Sudan 4 (according to the Okamoto method), the infiltration of the vessel with fatty inclusions is depicted, the vessels were stained using the Okamoto method, magnification × 100; Fig.9 in the group of rats with D+AH when staining the femoral artery with Sudan 4 (according to the Okamoto method) shows infiltration of the vessel with fatty inclusions, magnification x 400; Fig. 10 shows a graph of the thickness of the walls and intima of the aorta and femoral arteries of rats in the hyperlipidemia model (group I) and in a complex model: hyperlipidemia and arterial hypertension (group II).
Example of a specific implementation
The material for the experimental studies was Wistar rats - 45 males weighing 200-250 g. The animals were divided into 2 groups:
Group 1 - 15 male rats were on a cholesterol diet for 6 months (prototype). The diet consisted of adding 1% cholesterol powder to the food, 10% margarine, 10 mg/kg Mercazolil and vitamin D - 2.5 IU per kg body weight of the rat.
Group 2 15 male rats 15 days before starting feeding with a similar atherogenic diet (adding cholesterol powder in the amount of 1%, 10% margarine, 10 mg/kg Mercazolil, and vitamin D - 2.5 IU per kg body weight of rats) to the food An operation was performed - ligating the renal pedicle of the left kidney with non-absorbable suture material and suturing the upper pole of the right kidney, leaving 2/3 of the organ (the claimed method). This operation develops persistent renovascular arterial hypertension by 8-10 weeks of the experiment.
Group III - control - 15 healthy male rats ate a normal diet. After 6 months of the study, the animals of each group were removed from the experiment under ether anesthesia by decapitation. Blood serum, fragments of the aorta, femoral arteries and PBS were collected. The experiment was carried out in strict compliance with the requirements of the European Convention (Strasbourg, 1986) for the maintenance, feeding and care of experimental animals, as well as their removal from the experiment and subsequent disposal. The experiments were carried out in accordance with the requirements of the World Society for the Protection of Animals (WSPA) and the European Convention for the Protection of Experimental Animals. The study was approved by the interdisciplinary ethics committee (protocol No. 4, case No. 21 dated January 24, 2011).
Determination of OX content; TG; LDL and HDL cholesterol measurements were carried out using a standard colorimetric method using Olvex Diagnosticum reagents (Russia).
Blood pressure was measured in the tail artery using an MLU/4C 501 analyzer (MedLab China). During the experiment, the animals were under anesthesia, which relieved them of anxiety and associated pressure surges.
The magnetic resonance imaging method is as follows.
Before scanning, animals were euthanized with solutions of Rometar (Xylazinum, SPORA, PRAHA) at a concentration of 1 mg/ml and Relanium at a concentration of 2 mg/ml, intraperitoneally. MRI diagnostics were performed on a tomograph for experimental research “PharmaScan US 70/16” (Bruker, Germany) with a magnetic field strength of 7.0 Tesla, a frequency of 300 MHz and a BGA 09P coil. For angiography, the Head_Angio protocol was used with the following parameters: TR/TE=50.0/5.6; tilt angle 25.0; image field 3.0/3.0/3.0; effective cutting thickness 30 mm; overlap 30.0 mm; matrix 256/256/64 elements; one signal averaging, scanning time 14 min.
Histological preparations were fixed in 10% neutral formalin and embedded in paraffin. Sections were stained with hematoxylin and eosin, Van Gieson, Mallory, and Sudan-4 (Okamoto method). The description of micropreparations was carried out on an Olympus BX 41 microscope. Pictures were taken with an Olympus DP 12 electronic camera, at a constant magnification of 100 and 400. Morphometry was carried out using an eyepiece micrometer MOB - 1-16 ×.
The experiment used a histochemical method for NADPH diaphorase according to the standard recipe of Hope and Vincent (1989): fragments of animal vessels were isolated using a blade and immersed in cooled, 4% paraformaldehyde prepared in 0.1 M phosphate buffer (pH 7.4), which Of the entire class of diaphorases, only NADPH diaphorase retains activity. The material was fixed for 2 hours at a temperature of 4°C, washed for 24 hours at the same temperature in a 15% sucrose solution, changing the solution 7-8 times. From tissue samples frozen in a cryostat, sections 10 μm thick were prepared, mounted on glass slides, and placed in incubation medium. The composition and final concentration of the medium were as follows: 50 mM Tris buffer (pH 8.0), 1 mM NADPH (Sigma), 0.5 mM nitroblue tetrazolium (Sigma), and 0.2% Triton X-100 ( "Serva") Incubation was carried out for 60 minutes in a thermostat at a temperature of 37°C. Then the sections were rinsed in distilled water, dehydrated and embedded in balm according to the generally accepted method in histology.
Enzyme activity was measured in the endothelium and smooth myocytes of the aorta, femoral arteries and microvessels of the PBS of rats.
Enzyme activity was determined using the "ImageJ1.37 v" program and expressed in optical density units. There is evidence of a direct relationship between the concentration of the enzyme under study and the optical density of the precipitate formed as a result of the histochemical reaction.
For mathematical processing of the obtained data, the SPSS v program was used. 16. Comparison of mean values in samples was carried out using the nonparametric Wilcoxon-Mann-Whitney U test.
Blood pressure monitoring showed that in experimental group II (D+AG) blood pressure was higher than in group I and in the group of healthy rats throughout the experiment (2, 4, 6 months), which confirms the formation of renovascular and renoprival mechanisms of arterial hypertension (Table 1).
| Table 1 | ||||||
| Indicators of blood pressure in rats in models of experimental atherosclerosis | ||||||
| Groups of rats | Experiment 2 months | Experiment 4 months | Experiment 6 months | |||
| Systolic Blood pressure (mm Hg) | Diastolic Blood pressure (mm Hg) | Systolic Blood pressure (mm Hg) | Diastolic Blood pressure (mm Hg) | Systolic Blood pressure (mm Hg) | Diastolic Blood pressure (mm Hg) | |
| Group I (IG) | 113.8±3.6 | 68.8±1.22 | 122.06±1.05 | 66.18±7.08 | 141.70±4.41 | 90.89±1.83 |
| Group II (D+AG) | 131.3±1.5;* | 83.4±3.2;* | 140.12±3.25;* | 90.24±4.44;* | 161.70±1.66;* | 99.33±3.41;* |
| Group III (control) | 115.1±0.7 | 73.4±0.53 | 116.25±0.84 | 70.20±2.18 | 116.01±3.05 | 71.44±1.70 |
| *- significance of differences between groups I and II (pu<0,05); | ||||||
| - reliability between experimental groups and control group (р u<0,05). |
When studying the lipid spectrum in experimental groups of rats after 2 months of the experiment, an increase in the level of TC, TG, LDL, HDL and KA was found compared to the control group (p u<0,05) (таблица 2). При этом в группе крыс с артериальной гипертензией значения ОХ, ЛПНП, ЛПВП и КА были достоверно выше (р u <0,05), а уровень ТГ - несколько ниже (p u >0.05) than in the group of rats with isolated hyperlipidemia (Table 2). At the 4th month of the experiment in group I rats, lipid profile disorders persisted, and the LDL level significantly increased (p u<0,05). Во II группе значения ЛПВП и ЛПНП снизились и стали ниже, чем в I группе животных, при этом происходило увеличение уровня ТГ и КА. К 6 месяцу эксперимента в обеих опытных группах животных достоверно нарастал уровень ОХ и ТГ. У крыс с атерогенной диетой к этому периоду эксперимента отмечалось увеличение содержания липопротеинов высокой плотности по сравнению с их уровнем на 4 месяце исследования, при этом значения ЛПНП и КА не повышались (р u <0,05), тогда как во II группе крыс (Д+АГ) продолжалась тенденция снижения показателей ЛПНП и ЛПВП. При этом уровень ЛПВП у крыс данной группы стал ниже, чем у здоровых крыс (р u <0,05), произошло увеличение КА - в 2,5 раза по сравнению с I группой и в 4,8 раза по сравнению с контрольной группой крыс (таблица 2). Выявленные изменения подтверждают более выраженные нарушения липидного спектра у крыс II группы (Д+АГ). Снижение сывороточного содержания ЛПНП и ЛПВП у крыс с артериальной гипертензией и гиперлипидемией, вероятно, указывает на усиление их рецепции эндотелием сосудов.
When assessing vascular NADPH diaphorase, it was found that in the femoral arteries of the first experimental and control group of animals the content of NADPH diaphorase was lower than in the aorta, which can be explained by the anatomical features of the structure of the walls of these vessels (in the femoral arteries the muscular component is more pronounced) (p u<0,05). В бедренных артериях II группы крыс значения NADPH-диафоразы были несколько ниже, чем в аорте, однако показатели не имели достоверной разницы, что может свидетельствовать о более выраженном нарушении синтеза этого кофермента в аорте при моделировании реноваскулярной гиперетензии. При мониторинге NADPH-диафоразы зарегистрировано снижение ее уровня во фрагментах аорты и бедренных артерий I и II опытных групп крыс с достоверностью различий с контролем (р u <0,05) (табл.3).
There were no significant differences in the content of vascular coenzyme depending on the time of the experiment (2, 4, 6 months) in all experimental groups. The greatest decrease in NADPH diaphorase levels was determined at month 2 of the study, with relative stabilization of coenzyme values at a low level during subsequent monitoring.
In rats with hyperlipidemia and arterial hypertension, the value of NADPH-diaphorase in the dynamics of the entire experiment was lower than in the prototype (p u<0,05), что свидетельствует о более глубоком нарушении функциональных свойств эндотелия. У крыс II группы уровень NADPH-диафоразы в сосудах микроциркуляторного русла снижался ко 2 месяцу исследования, тогда как в группе крыс I группы (ЭГ) достоверное снижение его уровня происходило только к 6 месяцу эксперимента.
When monitoring the state of the arterial bed using magnetic resonance imaging (MRI), it was found that at the 2nd month of the study in experimental rats, the width of the common carotid artery, brachiocephalic trunk and thoracic aorta increased (Table 4, Fig. 1, Fig. 2). This vascular reaction is due to the inclusion of protective and adaptive mechanisms to maintain central hemodynamics.
However, by the 6th month of the experiment, a narrowing of the lumen of the listed vessels was noted (Table 4), most pronounced in group II of rats (reliability of differences with group I (p u<0,05). У крыс II группы регистрировалось уменьшение ширины просвета подвздошных артерий, что свидетельствует о мультифокальности поражения артериального русла при комплексном действии гиперлипидемии и артериальной гипертензии. Определялось неравномерное контрастирование артерий в моделе Д+АГ, что предполагает локальные атерогенные изменения стенки артерий (фиг.2).
| Table 4 | ||||||
| Diameter of the lumen of blood vessels in rats (mm), determined by MRI. | ||||||
| Vessels | I (diet) | Group II (diet + surgery) | Control (size in mm) | |||
| 2 months | 6 months | 2 months | 6 months | 2 months | 6 months | |
| General sleepiness | 1,57(1,49-1,63)! | 1,41(1,38-1,54) | 1,34;(1,26-1,47) | 1,14;(1,10-1,19) | 1,27(1,19-1,32) | 1,23(1,20-1,31) |
| Internal sleepy | 0,79(0,76-0,81) | 0,72(0,70-0,73) | 0,78(0,76-0,84) | 0,44(0,42-0,50) ! | 0,8(0,78-0,89) | 0,77(0,75-0,91) |
| Brachiocephalic trunk | 1,54(1,51-1,58)! | 1,38(1,43-1,50) | 1,47(1,60-1,65)! | 1,23(1,21-1,25) | 1,31(1,28-1,33) | 1,30(1,27-1,32) |
| Cerebral arteries | 0,49(0,46-0,56) | 0,40(0,38-0,41) | 0,49(0,45-0,52) | 0,44(0,42-0,50) | 0,40(0,37-0,47) | 0,41(0,39-0,44) |
| Gr. part of the aorta | 2,13(2,05-2,16)! | 1.78(1.76-1.79)× | 2,32(2,26-2,33)! | 1.51; (1.47-1.53) !× | 1,95(1,83-1,97) | 1,86(1,80-1,93) |
| Br. part of the aorta | 1,61 | 1,41 | 1,66 | 1,64 | 1,62(1,54-1,63) | |
| (1,59-1,63) | (1,40-1,44) | (1,60-1,68) | 1,53(1,43-1,56) | (1,60-1,66) | ||
| Common iliac arteries | 1,1(0,94-1,05) | 0,82(0,80-0,87) | 0,94(0,92-0,96) | 0.74(0.71-0.75)!× | 0,98(0,96-1,2) | 0,93(0,90-0,99) |
| Note: data presented as Median (NK-VK). | ||||||
| ! - reliability between experimental groups and control group (р u<0,05). | ||||||
| - reliability of differences between groups I and II (p u<0,05); | ||||||
| × - reliability of differences between indicators at 2 and 6 months of the experiment. |
An assessment of the histological structure of the arterial wall showed that the most pronounced changes in blood vessels are recorded by the 6th month of the experiment. In the aorta and femoral arteries of experimental rats, when stained with hematoxylin and eosin, changes in the architectonics of elastic fibers are observed, perinuclear optically empty formations are visualized, displacement of myocyte nuclei to the periphery, their compaction, cellular infiltration of the wall, thickening of the endothelium (Fig. 3, Fig. 4, Fig. 6) compared to intact rats (Fig. 5, Fig. 7). In this case, the most pronounced changes in the morphology of the arteries are recorded in the second experimental group (D + AG) (Fig. 4, Fig. 6). When arteries were stained with Sudan 4 using the Okamoto method in experimental rats with D+AH, infiltration of the vessel with fatty inclusions was revealed. In this case, fat deposition fills the voids identified by staining with hematoxylin and eosin (Fig. 8, Fig. 9).
In the PBS in experimental rats, a decrease in the number of microvessels is observed (in group I rats, 5-7 microvessels are detected, in group II - 3-4 microvessels in the field of view, while in control rats - 8-10 microvessels). The vessels of the microvasculature in rats of experimental group II are in the form of streaks with proliferation of endothelial cells, while in control rats they are oval or round in shape. The thickness of the microvessels of the anterior abdominal wall increased in the experimental groups of rats. At the same time, the maximum thickening of the microvascular wall was observed in experimental group II (M = 4.62 (4.36-4.72) µm in the second group, M = 2.31 (2.12-2.36) µm in group I, and 1.54 (1.50-1.62) µm - in control rats). An increase in the wall thickness of the aorta and femoral arteries was recorded in experimental rats. In rats with arterial hypertension, an increase in the thickness of the wall and intima of blood vessels was recorded, compared with the model of isolated experimental hyperlipidemia (Fig. 10).
A comparative analysis of the proposed solution with the prototype shows that in the claimed method, combining arterial hypertension and hyperlipidemia, by the 6th month of the experiment, changes in the lipid spectrum of the blood serum were established (increased levels of OX, TG, decreased HDL, increased KA) compared to the prototype. The inventive method makes it possible to establish a persistent increase in systolic and diastolic blood pressure from 2 to 6 months of the study. Compared to the prototype, a decrease in NADPH-diaphorase activity in the vascular endothelium was recorded by the 6th month of the experiment. Vascular damage was observed: deformation of elastic fibers, increase in the thickness of the wall and intima, cellular infiltration, deposition of fatty inclusions in the wall, narrowing of the lumen of blood vessels, and a decrease in the number of microvessels of the ASP.
A method for modeling atherosclerosis, including feeding the study animals an atherogenic diet, consisting of adding cholesterol powder in an amount of 1%, margarine 10%, Mercazolil 10 mg/kg and vitamin D - 2.5 IU per kg body weight of the rat, to the feed, characterized in that Along with feeding an atherogenic diet, the animals undergo an operation consisting of ligating the renal pedicle of the left kidney with non-absorbable suture material and suturing the upper pole of the right kidney, leaving 2/3 of the organ.
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125. Atherosclerosis, its etiology and pathogenesis. The role of impaired LDL-receptor interaction in the mechanisms of atherosclerotic plaque formation. Basic experimental models of atherosclerosis.
Atherosclerosis - various combinations of changes in the intima of the arteries, manifested in the form of focal deposition of lipids, complex carbohydrate compounds, blood elements and products circulating in it, the formation of connective tissue and calcium deposition.
Experimental models
IN 1912 N. N. Anichkov and S. S. Khalatov proposed a method for modeling atherosclerosis in rabbits by introducing cholesterol inside (through a tube or by mixing it with regular food). Pronounced atherosclerotic changes develop after several months with daily use of 0.5 - 0.1 g of cholesterol per 1 kg of body weight. As a rule, they are accompanied by an increase in the level of cholesterol in the blood serum (3-5 times compared to the initial level), which was the basis for the assumption of the leading pathogenetic role of hypercholesterolemia in the development of atherosclerosis. This model is easily reproducible not only in rabbits, but also in chickens, pigeons, monkeys, and pigs.
In dogs and rats resistant to the action of cholesterol, atherosclerosis is reproduced by the combined effect of cholesterol and methylthiouracil, which suppresses thyroid function. This combination of two factors (exogenous and endogenous) leads to prolonged and severe hypercholesterolemia (over 26 mmol/l-1000 mg%). Adding butter and bile salts to food also contributes to the development of atherosclerosis.
In chickens (roosters), experimental atherosclerosis of the aorta develops after prolonged exposure to diethylstilbestrol. In this case, atherosclerotic changes appear against the background of endogenous hypercholesterolemia, resulting from a violation of the hormonal regulation of metabolism.
Etiological factors :
heredity
gender (at the age of 40 - 80 years, men suffer from atherosclerosis and myocardial infarction of an atherosclerotic nature more often than women (on average 3 - 4 times). After 70 years, the incidence of atherosclerosis among men and women is approximately the same.)
age (> 30 years)
endogenous
2. exogenous
physical inactivity
intoxication (alcohol, nicotine, chemicals)
arterial hypertension (BP > 160/90)
hormonal disorders, metabolic diseases (diabetes mellitus, myxedema, ↓ function of the gonads, gout, obesity, hypercholesterolemia)
excess nutrition (lots of dietary fats and foods containing cholesterol)
Pathogenesis :
Existing theories of the pathogenesis of atherosclerosis can be reduced to two, fundamentally different in their answers to the question: what is primary and what is secondary in atherosclerosis, in other words, what is the cause and what is the consequence - lipoidosis of the inner lining of the arteries or degenerative-proliferative changes in the latter. This question was first posed by R. Virkhov (1856). He was the first to answer it, pointing out that “under all conditions, the process probably begins with a certain loosening of the connective tissue basic substance, of which the inner layer of the arteries mostly consists.”
Since then, the idea of the German school of pathologists and its followers in other countries originated, according to which, with atherosclerosis, dystrophic changes in the inner lining of the artery wall initially develop, and the deposition of lipids and calcium salts is a secondary phenomenon. The advantage of this concept is that it is able to explain the development of spontaneous and experimental atherosclerosis both in cases where there are disorders of cholesterol metabolism, and in those (which is especially important) when they are not. The authors of this concept assign a primary role to the arterial wall, i.e., the substrate that is directly involved in the pathological process. “Atherosclerosis is not only and not so much a reflection of general metabolic changes (in the laboratory they can even be elusive), but rather a derivative of the own structural, physical and chemical transformations of the substrate of the arterial wall... The primary factor leading to atherosclerosis lies precisely in the arterial wall itself , in its structure and in its enzyme system" (I.V. Davydovsky, 1966).
In contrast to these views, since the experiments of N. N. Anichkov and S. S. Khalatov, mainly thanks to the research of Soviet and American authors, the concept of the role in the development of atherosclerosis of general metabolic disorders in the body, accompanied by hypercholesterolemia, hyperlipemia and hyperbetalipoproteinemia, has been successfully developed. From this point of view, early atherosclerosis is a consequence of the primary diffuse infiltration of lipids, in particular cholesterol, into the unchanged inner lining of the arteries. Further changes in the vascular wall (the phenomena of mucoid edema, dystrophic changes in the fibrous structures and cellular elements of the subendothelial layer, productive changes) develop due to the presence of lipids in it, i.e. they are secondary.
Initially, the leading role in increasing the level of lipids, especially cholesterol, in the blood was attributed to the nutritional factor (excessive nutrition), which gave the name to the corresponding theory of the occurrence of atherosclerosis - nutritional. However, very soon it had to be supplemented, since it became obvious that not all cases of atherosclerosis can be put in a causal relationship with nutritional hypercholesterolemia. According to the combination theory of N. N. Anichkov, in the development of atherosclerosis, in addition to the nutritional factor, endogenous disorders of lipid metabolism and its regulation, mechanical effects on the vessel wall, changes in blood pressure, mainly its increase, as well as dystrophic changes in the arterial wall itself are important . However, even in this modification, the previous formula “without cholesterol there is no atherosclerosis” retained its original meaning. This is due to the fact that the development of atherosclerosis is primarily associated with the level of cholesterol in the blood serum.
In subsequent years, it was shown that for the occurrence of atherosclerosis, not only an increase in the cholesterol content in the blood serum is important, but also a change in the ratio between the levels of cholesterol and phospholipids (normally 0.9). With atherosclerosis, this ratio increases. Phospholipids reduce the cholesterol content in blood serum, keep it in an emulsified state, and prevent deposition in the wall of blood vessels. Thus, their relative deficiency is one of the important contributing factors to atherogenesis.
An equally important role is played by the qualitative composition of fat entering the body. Typically, 2/3 of the cholesterol introduced into the body enters into a chemical (ester) bond with fatty acids (mainly in the liver) to form cholesterol esters. Esterification of cholesterol with unsaturated fatty acids (linoleic, linolenic, arachidonic) contained in vegetable oils and fish oil promotes the formation of polar labile, easily soluble and catabolizable cholesterol esters. On the contrary, esterification of cholesterol with saturated fatty acids, mainly of animal origin (stearic, palmitic), contributes to the appearance of poorly soluble cholesterol esters that easily fall out of solution. In addition, the ability of unsaturated fatty acids to reduce the level of cholesterol in the blood serum by accelerating its excretion and metabolic transformations, and of saturated fatty acids, is known to increase it. The above facts allow us to conclude that a decrease in the ratio of unsaturated and saturated fatty acids contributes to the development of atherosclerosis. Serum lipids (cholesterol, cholesteryl esters, phospholipids, triglycerides) partly consist of chylomicrons (fine particles not dissolved in plasma) and lipoproteins - complexes of α- and β-globulins and lipids dissolved in plasma. α-Lipoproteins are approximately 33-60% protein and 40-67% fat, (β-lipoproteins are approximately 7-21% and 79-93%, respectively.
In atherosclerosis, the content of β-lipoproteins is increased, primarily with a low specific gravity (0.99-1.023). These lipoproteins float at a speed of 10-20 Sf, are characterized by an increased content of cholesterol and saturated fatty acids, a relative deficiency of phospholipids, and easily precipitate. A more complete physical and pathophysiological characterization, as well as classification of the types of atherogenic lipoproteins and corresponding hyperlipoproteinemias, was carried out by Fredrickson et al (1967).
It is obvious that the type of “transport” that ensures the delivery of cholesterol to the vascular wall during atherosclerosis is of significant importance both in the mechanism of occurrence of atherosclerotic lesions, determining their nature and severity, and for differentiated dietary and drug therapy.
In addition, taking into account the ability of atherogenic β-lipoproteins, after their penetration into the vascular wall, to complex with acidic glycosaminoglycans and glycoproteins, acquiring antigenic properties, the possibility of producing autoantibodies and the development of a pathological process of the autoimmune type is allowed. This may also be facilitated by the appearance of autoantigens from the decay products of atherosclerotic plaques, which provide specific sensitization of the body.
In recent years, much attention has been paid to the study of plasma and tissue enzymes that break down lipids. It has been established that lipolytic activity in animals resistant to nutritional cholesterol atherosclerosis (rats, dogs) is increased and, on the contrary, in animals susceptible to this disease (rabbits, chickens, pigeons) it is decreased.
In humans, due to age, as well as atherosclerosis, the lipolytic activity of the aortic wall decreases. This makes it possible to assume that in the complex system of mechanisms contributing to the development of vascular lipoidosis in atherosclerosis, a certain role is played by the deficiency of lipolytic enzymes.
The processes of cholesterol biosynthesis are of great importance in the pathogenesis of atherosclerosis. The latter is formed in the animal body through the stage of active acetate (acetyl-CoA) from proteins, fats and carbohydrates. The liver is the main organ that synthesizes cholesterol in the body. The vascular wall is also not devoid of the ability to synthesize cholesterol from acetate. Phospholipids and some fatty acids can be formed in it. However, the vascular wall is not able to provide the formation of the amount of lipids that is found in it during atherosclerosis. Their main source is blood serum. Consequently, the development of atherosclerosis without excessive intake of cholesterol from the outside can be explained by endogenous hypercholesterolemia, hyperlipemia and hyperbetalipoproteinemia.
The above concepts of the pathogenesis of atherosclerosis have their strengths and weaknesses. The most valuable advantage of the concept of general metabolic disorders in the body and primary lipoidosis of the arterial wall is the presence of an experimental cholesterol model. The concept of the primary significance of local changes in the arterial wall, despite the fact that it was expressed 100 years ago, does not yet have a convincing experimental model.
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The original meaning of the concept "atherosclerosis", proposed by Marchand in 1904, came down to only two types of changes: the accumulation of fatty substances in the form of mushy masses in the inner lining of the arteries (from the Greek athere - porridge) and sclerosis itself - a connective tissue thickening of the artery wall (from the Greek scleras - hard). The modern interpretation of atherosclerosis is much broader and includes ... “various combinations of changes in the intima of the arteries, manifested in the form of focal deposition of lipids, complex carbohydrate compounds, blood elements and products circulating in it, the formation of connective tissue and calcium deposition” (WHO definition).
Sclerotic vessels (the most common location is the aorta, arteries of the heart, brain, lower extremities) are characterized by increased density and fragility. Due to a decrease in elastic properties, they are not able to adequately change their lumen depending on the need of an organ or tissue for blood supply.
Initially, the functional inferiority of sclerotically altered vessels, and therefore organs and tissues, is detected only when increased demands are placed on them, i.e., when the load increases. Further progression of the atherosclerotic process can lead to decreased performance at rest.
A strong degree of atherosclerotic process is usually accompanied by narrowing and even complete closure of the lumen of the arteries. With the slow sclerosis of arteries in organs with impaired blood supply, atrophic changes occur with the gradual replacement of functionally active parenchyma by connective tissue.
Rapid narrowing or complete closure of the lumen of the artery (in the case of thrombosis, thromboembolism or hemorrhage into the plaque) leads to necrosis of the organ area with impaired blood circulation, i.e. to a heart attack. Myocardial infarction is the most common and most dangerous complication of atherosclerosis of the coronary arteries.
Experimental models. In 1912, N. N. Anichkov and S. S. Khalatov proposed a method for modeling atherosclerosis in rabbits by introducing cholesterol inside (through a tube or by mixing it with regular food). Pronounced atherosclerotic changes developed after several months with daily use of 0.5 - 0.1 g of cholesterol per 1 kg of body weight. As a rule, they were accompanied by an increase in the level of cholesterol in the blood serum (3-5 times compared to the initial level), which was the basis for the assumption of a leading pathogenetic role in the development of atherosclerosis hypercholesterolemia. This model is easily reproducible not only in rabbits, but also in chickens, pigeons, monkeys, and pigs.
In dogs and rats resistant to the action of cholesterol, atherosclerosis is reproduced by the combined effect of cholesterol and methylthiouracil, which suppresses thyroid function. This combination of two factors (exogenous and endogenous) leads to prolonged and severe hypercholesterolemia (over 26 mmol/l - 100 mg%). Adding butter and bile salts to food also contributes to the development of atherosclerosis.
In chickens (roosters), experimental atherosclerosis of the aorta develops after long-term (4 - 5 months) exposure to diethylstilbestrol. In this case, atherosclerotic changes appear against the background of endogenous hypercholesterolemia, resulting from a violation of the hormonal regulation of metabolism.
Etiology. The given experimental examples, as well as observations of spontaneous human atherosclerosis and its epidemiology, indicate that this pathological process develops as a result of the combined action of a number of factors (environmental, genetic, nutritional). In each individual case, one of them comes to the fore. There are factors that cause atherosclerosis and factors that contribute to its development.
On rice. 19.12 a list of the main etiological factors (risk factors) of atherogenesis is given. Some of them (heredity, gender, age) are endogenous. They manifest their effect from the moment of birth (gender, heredity) or at a certain stage of postnatal ontogenesis (age). Other factors are exogenous. The human body encounters their effects at various age periods.
The role of hereditary factors The occurrence of atherosclerosis is confirmed by statistical data on the high incidence of coronary heart disease in individual families, as well as in identical twins. We are talking about hereditary forms of hyperlipoproteinemia, genetic abnormalities of cellular receptors for lipoproteins.
Floor. At the age of 40 - 80 years, men suffer from atherosclerosis and myocardial infarction of an atherosclerotic nature more often than women (on average 3 - 4 times). After 70 years, the incidence of atherosclerosis among men and women is approximately the same. This indicates that the incidence of atherosclerosis among women occurs at a later period. These differences are associated, on the one hand, with a lower initial level of cholesterol and its content mainly in the fraction of non-atherogenic a-lipoproteins in the blood serum of women, and on the other, with the anti-sclerotic effect of female sex hormones. A decrease in the function of the gonads due to age or for any other reason (removal of the ovaries, their irradiation) causes an increase in serum cholesterol levels and a sharp progression of atherosclerosis.
It is assumed that the protective effect of estrogens is reduced not only to the regulation of cholesterol in the blood serum, but also other types of metabolism in the arterial wall, in particular oxidative. This anti-sclerotic effect of estrogens manifests itself mainly in relation to the coronary vessels.
Age. A sharp increase in the frequency and severity of atherosclerotic vascular lesions due to age, especially noticeable after 30 years (see. rice. 19.12), gave rise to some researchers the idea that atherosclerosis is a function of age and is an exclusively biological problem [Davydovsky I.V., 1966]. This explains the pessimistic attitude towards a practical solution to the problem in the future. Most researchers, however, are of the opinion that age-related and atherosclerotic changes in blood vessels are various forms of arteriosclerosis, especially in the later stages of their development, but age-related changes in blood vessels contribute to its development. The effect of age, which promotes atherosclerosis, manifests itself in the form of local structural, physicochemical and biochemical changes in the arterial wall and general metabolic disorders (hyperlipemia, hyperlipoproteinemia, hypercholesterolemia) and its regulation.
Excessive nutrition. Experimental studies by N. N. Anichkov and S. S. Khalatov suggested the importance of the etiological role in the occurrence of spontaneous atherosclerosis of excess nutrition, in particular, excess intake of dietary fats. The experience of countries with a high standard of living convincingly proves that the more energy needs are met through animal fats and cholesterol-containing foods, the higher the cholesterol level in the blood and the incidence of atherosclerosis. On the contrary, in countries where animal fats account for a small part of the energy value of the daily diet (about 10%), the incidence of atherosclerosis is low (Japan, China).
In accordance with the program developed in the USA, based on these facts, reducing fat intake from 40% of total calories to 30% by the year 2000 should reduce mortality from myocardial infarction by 20 - 25%.
Stress. The incidence of atherosclerosis is higher among people in “stressful professions,” i.e. professions that require prolonged and strong nervous tension (doctors, teachers, lecturers, administrative staff, pilots, etc.).
In general, the incidence of atherosclerosis is higher among the urban population compared to the rural population. This can be explained by the fact that in a big city a person is more often exposed to neurogenic stress influences. Experiments confirm the possible role of neuropsychic stress in the occurrence of atherosclerosis. The combination of a high-fat diet with nervous tension should be considered unfavorable.
Physical inactivity. A sedentary lifestyle and a sharp decrease in physical activity (hypodynamia), characteristic of humans in the second half of the 20th century, are another important factor in atherogenesis. This position is supported by the lower incidence of atherosclerosis among manual workers and the higher incidence among people engaged in mental work; faster normalization of cholesterol levels in the blood serum after its excess intake from the outside under the influence of physical activity.
The experiment revealed pronounced atherosclerotic changes in the arteries of rabbits after placing them in special cages, which significantly reduced their motor activity. A combination of a sedentary lifestyle and excess nutrition poses a particular atherogenic danger.
Intoxication. The influence of alcohol, nicotine, intoxication of bacterial origin and intoxication caused by various chemicals (fluorides, CO, H 2 S, lead, benzene, mercury compounds) are also factors contributing to the development of atherosclerosis. In most of the intoxications examined, not only general disorders of fat metabolism characteristic of atherosclerosis were noted, but also typical dystrophic and infiltrative-proliferative changes in the arterial wall.
Arterial hypertension Apparently, it does not have independent significance as a risk factor. This is evidenced by the experience of countries (Japan, China), whose population often suffers from hypertension and rarely from atherosclerosis. However, high blood pressure is becoming increasingly important as a contributing factor to the development of atherosclerosis.
factor in combination with others, especially if it exceeds 160/90 mm Hg. Art. Thus, with the same cholesterol level, the incidence of myocardial infarction with hypertension is five times higher than with normal blood pressure. In an experiment on rabbits whose food was supplemented with cholesterol, atherosclerotic changes develop faster and reach a greater extent against the background of hypertension.
Hormonal disorders, metabolic diseases. In some cases, atherosclerosis occurs against the background of previous hormonal disorders (diabetes mellitus, myxedema, decreased function of the gonads) or metabolic diseases (gout, obesity, xanthomatosis, hereditary forms of hyperlipoproteinemia and hypercholesterolemia). The etiological role of hormonal disorders in the development of atherosclerosis is also evidenced by the above experiments on the experimental reproduction of this pathology in animals by influencing the endocrine glands.
Pathogenesis. Existing theories of the pathogenesis of atherosclerosis can be reduced to two, fundamentally different in their answers to the question: what is primary and what is secondary in atherosclerosis, in other words, what is the cause and what is the consequence - lipoidosis of the inner lining of the arteries or degenerative-proliferative changes in the latter. This question was first raised by R. Virchow (1856). He was the first to answer it, pointing out that “under all conditions, the process probably begins with a certain loosening of the connective tissue basic substance, of which the inner layer of the arteries mostly consists.”
Since then, the idea of the German school of pathologists and its followers in other countries began, according to which, with atherosclerosis, dystrophic changes in the inner lining of the artery wall initially develop, and the deposition of lipids and calcium salts is a secondary phenomenon. The advantage of this concept is that it is able to explain the development of spontaneous and experimental atherosclerosis both in cases where there are pronounced disorders of cholesterol metabolism, and in their absence. The authors of this concept assign a primary role to the arterial wall, i.e., the substrate that is directly involved in the pathological process. “Atherosclerosis is not only and not so much a reflection of general metabolic changes (in the laboratory they can even be elusive), but a derivative of the own structural, physical and chemical transformations of the substrate of the arterial wall... The primary factor leading to atherosclerosis lies precisely in the arterial wall itself , in its structure and in its enzyme system" [Davydovsky I.V., 1966].
In contrast to these views, since the experiments of N.N. Anichkov and S.S. Khalatov, mainly thanks to the research of domestic and American authors, the concept of the role in the development of atherosclerosis of general metabolic disorders in the body, accompanied by hypercholesterolemia, hyper- and dyslipoproteinemia, has been successfully developed. From this point of view, atherosclerosis is a consequence of the primary diffuse infiltration of lipids, in particular cholesterol, into the unchanged inner lining of the arteries. Further changes in the vascular wall (the phenomena of mucoid edema, dystrophic changes in the fibrous structures and cellular elements of the subendothelial layer, productive changes) develop due to the presence of lipids in it, i.e. they are secondary.
Initially, the leading role in increasing the level of lipids, especially cholesterol, in the blood was attributed to the nutritional factor (excessive nutrition), which gave the name to the corresponding theory of the occurrence of atherosclerosis - nutritional. However, very soon it had to be supplemented, since it became obvious that not all cases of atherosclerosis can be put in a causal relationship with nutritional hypercholesterolemia. According to combination theory N. N. Anichkova, in the development of atherosclerosis, in addition to the nutritional factor, endogenous disorders of lipid metabolism and its regulation, mechanical effects on the vessel wall, changes in blood pressure, mainly its increase, as well as dystrophic changes in the arterial wall itself are important. In this combination of causes and mechanisms of atherogenesis, some (nutritional and/or endogenous hypercholesterolemia) play the role of an initial factor. Others either provide an increased supply of cholesterol into the vessel wall or reduce its excretion from it through the lymphatic vessels.
In the blood, cholesterol is contained in chylomicrons (fine particles not dissolved in plasma) and lipoproteins - supramolecular heterogeneous complexes of triglycerides, cholesterol esters (core), phospholipids, cholesterol and specific proteins (apoproteins: APO A, B, C, E), forming surface layer. There are certain differences between lipoproteins in size, core-to-shell ratio, qualitative composition and atherogenicity.
Four main fractions of blood plasma lipoproteins have been identified depending on density and electrophoretic mobility.
Noteworthy is the high protein content and low lipid content in the fraction of high-density lipoproteins (HDL - α-lipoproteins) and, conversely, the low protein content and high - lipid content in the fractions of chylomicrons, very low-density lipoproteins (VLDL - pre-β-lipoproteins ) and low-density lipoproteins (LDL - β-lipoproteins).
Thus, blood plasma lipoproteins deliver cholesterol and triglycerides synthesized and obtained from food to the places of their use and storage.
HDL has an antiatherogenic effect by reverse transport of cholesterol from cells, including from blood vessels, to the liver with subsequent excretion from the body in the form of bile acids. The remaining fractions of lipoproteins (especially LDL) are atherogenic, causing excessive accumulation of cholesterol in the vascular wall.
IN table 5 The classification of primary (genetically determined) and secondary (acquired) hyperlipoproteinemia with varying degrees of severity of atherogenic action is given. As follows from the table, the main role in the development of atheromatous changes in blood vessels is played by LDL and VLDL, their increased concentration in the blood, and excessive entry into the vascular intima.
Excessive transport of LDL and VLDL into the vascular wall results in damage to the endothelium.
In accordance with the concept of American researchers I. Goldstein and M. Brown, LDL and VLDL enter cells by interacting with specific receptors (APO B, E-glycoprotein receptors), after which they are endocytically captured and fused with lysosomes. In this case, LDL is broken down into proteins and cholesterol esters. Proteins are broken down into free amino acids, which leave the cell. Cholesterol esters undergo hydrolysis to form free cholesterol, which enters the cytoplasm from lysosomes and is subsequently used for various purposes (membrane formation, synthesis of steroid hormones, etc.). It is important that this cholesterol inhibits its synthesis from endogenous sources, in excess it forms “reserves” in the form of cholesterol esters and fatty acids, but, most importantly, through a feedback mechanism it inhibits the synthesis of new receptors for atherogenic lipoproteins and their further entry into the cell. Along with the regulated receptor-mediated mechanism of LP transport, which provides the internal needs of cells for cholesterol, interendothelial transport is described, as well as the so-called unregulated endocytosis, which is transcellular, including transendothelial vesicular transport of LDL and VLDL with subsequent exocytosis (into the intima of arteries from the endothelium, macrophages, smooth muscle cells).
Taking into account the stated ideas mechanism of the initial stage of atherosclerosis, characterized by excessive accumulation of lipids in the intima of the arteries, may be caused by:
1. Genetic anomaly of receptor-mediated endocytosis of LDL (absence of receptors - less than 2% of the norm, a decrease in their number - 2 - 30% of the norm). The presence of such defects was found in familial hypercholesterolemia (type II A hyperbetalipoproteinemia) in homo- and heterozygotes. A line of rabbits (Watanabe) with a hereditary defect in LDL receptors was bred.
2. Overload of receptor-mediated endocytosis in alimentary hypercholesterolemia. In both cases, there is a sharp increase in the unregulated endocytotic uptake of drug particles by endothelial cells, macrophages and smooth muscle cells of the vascular wall due to severe hypercholesterolemia.
3. Slowing down the removal of atherogenic lipoproteins from the vascular wall through the lymphatic system due to hyperplasia, hypertension, and inflammatory changes.
A significant additional point is the various transformations (modifications) of lipoproteins in the blood and vascular wall. We are talking about the formation under conditions of hypercholesterolemia of autoimmune complexes of LP - IgG in the blood, soluble and insoluble complexes of LP with glycosaminoglycans, fibronectin, collagen and elastin in the vascular wall (A. N. Klimov, V. A. Nagornev).
Compared with native drugs, the uptake of modified drugs by intimal cells, primarily macrophages (via cholesterol-unregulated receptors), increases sharply. This is believed to be the reason for the transformation of macrophages into so-called foam cells, which form the morphological basis lipid stain stages and with further progression - atherom. The migration of blood macrophages into the intima is ensured by the monocyte chemotactic factor, formed under the influence of LP and interleukin-1, which is released from the monocytes themselves.
At the final stage, they are formed fibrous plaques as a response of smooth muscle cells, fibroblasts and macrophages to damage, stimulated by growth factors of platelets, endothelial cells and smooth muscle cells, as well as the stage of complicated lesions - calcification, thrombus formation etc. ( rice. 19.13).
The above concepts of the pathogenesis of atherosclerosis have their strengths and weaknesses. The most valuable advantage of the concept of general metabolic disorders in the body and primary lipoidosis of the arterial wall is the presence of an experimental cholesterol model. The concept of the primary significance of local changes in the arterial wall, despite the fact that it was expressed more than 100 years ago, does not yet have a convincing experimental model.
As can be seen from the above, in general they can complement each other.
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Topic: Experimental atherosclerosis
1. Introduction: Experimental atherosclerosis
2. Vascular lesions that develop due to nutritional disorders
3. Changes in the aorta with hypervitaminosis D
4. Necrosis and aneurysms of the aorta in rats
5. Necrotizing arteritis
6. Vascular changes due to insufficient protein in food
7. Dystrophic-sclerotic changes in blood vessels obtained with the help of certain chemicals
8. Aortitis obtained by mechanical thermal and infectious damage to the vascular wall
Literature
INTRODUCTION: EXPERIMENTAL ATHEROSCLEROSIS
Experimental reproduction of vascular changes similar to human atherosclerosis is achieved by feeding animals with food rich in cholesterol or pure cholesterol dissolved in vegetable oil. In the development of an experimental model of atherosclerosis, the studies of Russian authors were of greatest importance.
In 1908 A.I. Ignatovsky was the first to establish that when rabbits are fed animal food, changes develop in the aorta that are very reminiscent of human atherosclerosis. In the same year A.I. Ignatovsky together with L.T. Mooro created a classic model of atherosclerosis, showing that when rabbits are fed egg yolk for 1y2-61/2 months, atheromatosis of the aorta develops, which, starting in the intima, moves to the tunica media. These data were confirmed by L.M. Starokadomsky (1909) and N.V. Stukkeem (1910). N.V. Veselkin, S.S. Khalatov and N.P. Anichkov found that the main active part of yolks is cholesterol (A.I. Moiseev, 1925). After this, pure OH cholesterol began to be used along with yolks to obtain atherosclerosis. I. Anichkov and S.S Khalatov, 1913).
To obtain atherosclerotic changes in the aorta and large vessels, adult rabbits are fed daily for 3-4 months with cholesterol dissolved in sunflower oil. Cholesterol is dissolved in heated sunflower oil so that a 5--10% solution is obtained, which is introduced into the stomach heated to 35--40 °; Every day the animal receives 0.2-0.3 g of cholesterol per 1 kg of weight. If an exact dosage of cholesterol is not required, it is given mixed with vegetables. Within 1.5-2 weeks, the animals develop hypercholesterolemia, gradually reaching very high numbers (up to 2000 mg% with a norm of 150 mg%). In the aorta, according to N. N. Anichkov (1947), the following changes unfold. On the inner surface of the vessel, 3-4 weeks after the start of the experiment, oval-shaped spots and stripes, somewhat elevated, appear. Gradually (by 60-70 days) rather large plaques form, protruding into the lumen of the vessel. They appear primarily in the initial part of the aorta above the valves and in the arch at the mouths of the large cervical arteries; these changes subsequently spread along the aorta in the caudal direction (Fig. 14). Number and size of plaques
increase, they merge with each other to form continuous diffuse thickenings of the aortic wall. The same plaques form on the valves of the left heart, in the coronary, carotid and pulmonary arteries. Deposition of lipoids is observed in the walls of the central arteries of the spleen and in the small arteries of the liver.
T.A. Sinitsyna (1953) to obtain atherosclerosis of the main branches of the coronary arteries of the heart, fed rabbits for a long time with egg yolks (0.2 - 0.4 g of cholesterol) dissolved in milk, and at the same time injected them with 0.3 g of thiouracil. Each rabbit received 170-200 yolks during the experiment. Microscopic examination at an early stage reveals a diffuse accumulation of lipoids in the interstitial substance of the aortic wall, especially between the internal elastic lamina and the endothelium. Subsequently, large cells (polyblasts and macrophages) appear, accumulating lipid substances in the form of birefringent drops of cholesterolseters. At the same time, in places where lipoids are deposited, elastic fibers are formed in large quantities, split off from the internal elastic lamina and located between the cells containing lipoids. Soon, first collagen and then collagen fibers appear in these places (N.N. Anichkov, 1947).
In studies carried out under the leadership of N. N. Anichkov, the process of reverse development of the changes described above was also studied. If, after 3-4 months of feeding animals with cholesterol, its administration is stopped, then a gradual resorption of lipoids from plaques occurs, which in rabbits continues for over two years. At the sites of large lipid accumulations, fibrous plaques are formed, with lipid residues and cholesterol crystals in the center. Pollack (1947) and Fistbrook (1950) indicate that as the weight of animals increases, the severity of experimental atherosclerosis increases.
For a long time, rabbits remained the only animal species used to produce experimental atherosclerosis. This is explained by the fact that, for example, in dogs, when fed even large amounts of cholesterol, the level of cholesterol in the blood rises slightly and atherosclerosis does not develop. However, Steiner et al. (1949) showed that if you combine feeding dogs with cholesterol with a decrease in thyroid function, significant hypercholesterolemia occurs and atherosclerosis develops. The dogs were administered thiouracil with food daily for 4 months in increasing quantities: during the first two months, 0.8 g, during the third month, 1 g, and then 1.2 g. At the same time, the dogs received daily with food 10 g of cholesterol, which was previously dissolved in ether and mixed with food; food was given to the dogs after the ether had evaporated. Control experiments have shown that long-term administration of thiouracil or cholesterol alone to dogs does not cause either significant hypercholesterolemia (4-00 mg% when the norm is 200 mg%) or atherosclerosis. At the same time, when dogs are given thiouracil and cholesterol at the same time, severe hypercholesterolemia (up to 1200 mg%) and atherosclerosis develop.
The topography of atherosclerosis in dogs, to a much greater extent than in rabbits, resembles human atherosclerosis: the most pronounced changes are in the abdominal aorta, significant atherosclerosis is observed in the large branches of the coronary arteries of the heart with a significant narrowing of the lumen of the vessel (Fig. 15), many plaques are noticeable in the arteries of the brain . Huper (1946) injected dogs daily into the jugular vein with 50 ml of hydroxylcellulose solution of varying viscosity (5-6 times the viscosity of plasma) and observed the development of atheromatosis and degenerative changes in the tunica media in the aorta. When assessing the severity of experimental atherosclerosis, one should take into account the instructions of Lindsay et al. (1952, 1955), who found that significant arteriosclerosis often occurs in old dogs and cats. Lipoid deposits are usually insignificant, and cholesterol is not detected in them.
Bragdon and Boyle (1952) produced atherosclerosis in rats by intravenous injections of lipoproteins obtained from the serum of rabbits fed cholesterol. These lipoproteins were isolated, purified and concentrated by centrifugation at 30 thousand rpm with the serum salt concentration increased to 1063. Excess salt was then removed by dialysis. With repeated daily injections, rats develop significant lipoid deposits in the wall of the aorta and large vessels. Chaikov, Lindsay, Lorenz (1948), Lindsay, Nichols and Chaikov (1.955) obtained atherosclerosis in birds by periodically injecting them subcutaneously with 1-2 tablets of diethylstilbestrol (each tablet contained 12-25 mg of the drug); the experiment lasted for 10 months.
The developing atherosclerosis in topography and morphogenesis did not differ from cholesterol. According to these authors, atherosclerosis in birds can be obtained in the usual way - by feeding cholesterol.
Reproduction of atherosclerosis in monkeys often ended in failure (Kawamura, cited by Mann et al., 1953). However, Mann et al. (1953) managed to obtain pronounced atherosclerosis of the aorta, carotid and femoral arteries in apes when feeding them for 18-30 months with food rich in cholesterol, but containing insufficient amounts of methionine or cystine. Daily addition of 1 g of methionine to food prevents the development of atherosclerosis. Previously, Rinehart and Greenberg (1949) obtained atherosclerosis in monkeys when they were kept for 6 months on a diet with a high amount of cholesterol and insufficient pyridoxine.
The development of experimental atherosclerosis can be accelerated or, conversely, slowed down. A number of researchers have observed a more intense development of atherosclerosis when feeding animals with cholesterol in combination with experimental hypertension. So, N.N. Anichkov (1914) showed that when the lumen of the abdominal aorta narrows by V"--2/3, the development of atherosclerosis in rabbits receiving 0.4 g of cholesterol daily is significantly accelerated. According to N.I. Anichkov, more intense atherosclerotic changes can be obtained in animals by feeding them cholesterol and daily intravenous injections of a solution of 1: 1000 adrenaline in an amount of 0.1-0.15 ml for 22 days. Wilens (1943) gave rabbits 1 g of cholesterol daily (6 days a week) and placed them in an upright position for 5 hours (also 6 times a week), which led to an increase in blood pressure by 30-40%. The experiment lasted from 4 to 12 weeks; In these animals, atherosclerosis was significantly more pronounced than in controls (who were only fed cholesterol or placed in an upright position).
V.S. Smolensky (1952) observed a more intensive development of atherosclerosis in rabbits with experimental hypertension (narrowing of the abdominal aorta; wrapping one kidney with a rubber capsule and removing the other).
Yester, Davis and Friedman (1955) observed an acceleration of the development of atherosclerosis in animals when they were fed cholesterol in combination with repeated injections of epinephrine. The rabbits were given intravenous epinephrine daily at a rate of 25 mg per 1 kg of weight. This dose was increased after 3-4 days to 50 mg per 1 kg of weight. The injections lasted 15-20 days. During the same period, the animals received 0.6-0.7 g of cholesterol. The experimental animals showed more significant lipoid deposits in the aorta, compared to control rabbits that received only cholesterol.
Shmidtman (1932) showed the importance of increased functional load on the heart for the development of atherosclerosis of the coronary arteries. Rats received 0.2 g of cholesterol dissolved in vegetable oil daily with food. At the same time, the animals were forced to run on a treadmill every day. The experiment lasted for 8 months. Control rats received cholesterol, but did not run in the drum. In experimental animals, the heart was approximately 2 times larger than in control animals (mainly due to hypertrophy of the left ventricular wall); In them, atherosclerosis of the coronary arteries was especially pronounced: in some places the lumen of the vessel was almost completely closed by atherosclerotic plaque. The degree of development of atherosclerosis in the aorta in experimental and control animals was approximately the same.
K.K. Maslova (1956) found that when feeding rabbits with cholesterol (0.2 mg daily for 115 days) in combination with intravenous administration of nicotine (0.2 ml, 1% solution daily), lipoid deposition in the aortic wall occurs to a much greater extent, than in cases where rabbits receive only cholesterol. K.K. Maslova explains this phenomenon by the fact that dystrophic changes in blood vessels caused by nicotine contribute to a more intense accumulation of lipoids in their walls. Kelly, Taylor and Huss (1952), Prior and Hartmap (1956) indicate that in areas of dystrophic changes in the aortic wall (mechanical damage, short-term freezing), atherosclerotic changes are especially pronounced. At the same time, the deposition of lipoids in these places delays and distorts the course of restoration processes in the vessel wall.
A number of studies have shown the delaying effect of certain substances on the development of experimental atherosclerosis. Thus, when feeding rabbits with cholesterol and simultaneously giving them thyroidin, the development of atherosclerosis occurs much more slowly. V.V. Tatarsky and V.D. Zipperling (1950) found that thyroidin also promotes a more rapid reverse development of atheromatous plaques. Rabbits were given 0.5 g of cholesterol (0.5% solution in sunflower oil) into the stomach daily through a tube. After 3.5 months of feeding with cholesterol, thyroidin was started to be used: daily administration of 0.2 g of thyroidin in the form of an aqueous emulsion into the stomach through a tube for 1.5-3 months. In these rabbits, in contrast to the control ones (which were not injected with thyroidin), there was a steeper drop in hypercholesterolemia and a more pronounced reverse development of atheromatous plaques (fewer amounts of lipoids in the aortic wall, deposited mainly in the form of large droplets). Choline also has a retarding effect on the development of atherosclerosis.
Steiner (1938) gave rabbits 1 g of cholesterol 3 times a week with food for 3-4 months. In addition, the animals were given 0.5 g of choline daily in the form of an aqueous emulsion. It turned out that choli significantly delays the development of atherosclerosis. It has also been shown that under the influence of choline, a more rapid reversal of atheromatous plaques occurs (administration of choline to rabbits for 60 days after a preliminary 110-day feeding of cholesterol). Taper's data were confirmed by Bauman and Rush (1938) and Morrisop and Rosi (1948). Horlick and Duff (1954) found that the development of atherosclerosis is significantly delayed under the influence of heparin. Rabbits received 1 g of cholesterol daily with food for 12 weeks. At the same time, the animals received intramuscular injections of 50 mg of heparin daily. In treated rabbits, atherosclerosis was significantly less pronounced than in control rabbits that did not receive heparin. Similar results were previously obtained by Konstenides et al. (1953). Stumpf and Wilens (1954) and Gordon, Kobernik and Gardner (1954) found that cortisone delayed the development of atherosclerosis in rabbits fed cholesterol.
Duff and Mac Millap (1949) showed that in rabbits with alloxan diabetes the development of experimental atherosclerosis was significantly delayed. Rabbits were intravenously injected with a 5% aqueous solution of alloxyp (at the rate of 200 mg per 1 kg of weight). After 3-4 weeks (when diabetes developed), the animals were given cholesterol for 60-90 days (in total they received 45-65 g of cholesterol). In these animals, compared to control animals (without diabetes), atherosclerosis was significantly less pronounced. Some researchers have observed a sharp slowdown in the development of atherosclerosis in rabbits that, while receiving cholesterol, were exposed to general irradiation with ultraviolet rays. In these animals, the serum cholesterol content increased slightly.
Some vitamins have a significant effect on the development of atherosclerosis. It has been shown (A.L. Myasnikov, 1950; G.I. Leibman and E.M. Berkovsky, 1951) that the development of atherosclerosis is delayed under the influence of ascorbic acid. G.I. Leibman and E.M. Berkovsky gave rabbits 0.2 g of cholesterol per 1 kg of weight daily for 3 months. At the same time, the animals received daily ascorbic acid (0.1 g per 1 kg of weight). In these animals, atherosclerosis was less pronounced than in those that did not receive ascorbic acid. In rabbits receiving cholesterol (0.2 g daily for 3-4 months) in combination with vitamin D (10,000 units daily throughout the experiment), the development of atherosclerotic changes intensifies and accelerates (A.L Myasnikov, 1950).
According to Brager (1945), vitamin E promotes more intensive development of experimental cholesterol atherosclerosis: rabbits were given 1 g of cholesterol 3 times a week for 12 weeks; At the same time, intramuscular injections of 100 mg of vitamin E were given. All animals had higher hypercholesterolemia and more severe atherosclerosis compared to rabbits that did not receive vitamin E.
VASCULAR LESIONS DEVELOPING DURING NUTRITION DISORDERS. CHANGES IN THE AORTA WITH HYPERVITAMINOSIS D
Under the influence of large doses of vitamin D, animals develop pronounced changes in internal organs and large vessels. Kreitmayr and Hintzelman (1928) observed significant deposits of lime in the tunica media of the aorta in cats that were given 28 mg of irradiated ergosterol daily with food for a month (Fig. 16). Necrotic changes in the medial tunic of the aorta with subsequent calcification were discovered in rats by Dagaid (1930), who daily gave the animals 10 mg of irradiated ergosterol in a 1% solution in olive oil. Meessen (1952) gave rabbits 5000 sd for three weeks to obtain necrosis of the medial membrane of the aorta. vitamin Dg. Under these conditions, only microscopic changes occurred. Gilman and Gilbert (1956) discovered dystrophy of the middle tunica of the aorta in rats that were given 100,000 units for 5 days. vitamin D per 1 kg of weight. Vascular damage was more intense in animals that were given 40 mcg of thyroxine for 21 days before administration of vitamin D.
NECROSES AND ANEURYSMS OF THE AORTA IN RATS
When rats are fed for a long time with food containing large amounts of peas, dystrophic changes in the aortic wall develop with the gradual formation of an aneurysm. Bechhubur and Lalich (1952) fed white rats food containing 50% ground or coarse, unprocessed peas. In addition to peas, the diet included yeast, casein, olive oil, a salt mixture and vitamins. The animals were on a diet from 27 to 101 days. In 20 out of 28 experimental rats, an aortic aneurysm developed in the area of its arch. In some animals, the aneurysm ruptured with the formation of a massive hemothorax. Histological examination revealed edema of the medial membrane of the aorta, destruction of elastic fibers and minor hemorrhages. Subsequently, fibrosis of the wall developed with the formation of aneurysmal dilatation of the vessel. Panseti and Beard (1952) in similar experiments observed the development of an aneurysm in the thoracic aorta in 6 of 8 experimental rats. Along with this, the animals developed kyphoscoliosis, which arose as a result of dystrophic changes in the vertebral bodies. Five animals at 5-9 weeks died from aneurysm rupture and massive hemothorax.
Walter and Wirtschaftsr (1956) kept young rats (from 21 days after birth) on a diet of 50% peas; in addition, the diet included: maize, casein, milk salt powder, vitamins. All this was mixed and given to the animals. The latter were killed 6 weeks after the start of the experiment. In contrast to the experiments cited above, in these experiments there was damage to the porta not only in the area of the arch, but also in other parts, including the abdominal. Histologically, changes in blood vessels occurred in two parallel developing processes: degeneration and disintegration of the elastic framework, on the one hand, and fibrosis, on the other. Multiple intramural hematomas were usually observed. Significant changes also occurred in the pulmonary artery and coronary arteries of the heart. Some rats died due to aneurysm rupture; in a number of cases the latter had a delaminating character. Lulich (1956) showed that the described changes in the aorta are caused by P-amipopropiopitrite contained in peas.
NECROTIC ARTERITIS
Holman (1943, 1946) showed that in dogs kept on a diet rich in fat, renal failure leads to the development of necrotizing arteritis. The animals were given food in which 32 parts were beef liver, 25 parts - cane sugar, 25 parts - starch grains, 12 parts - oil, 6 parts - fish oil; Kaolin, salts and tomato juice were added to this mixture. The experiment lasted 7-8 weeks (the time required for the occurrence of vascular lesions in the presence of renal failure). Renal failure was achieved in various ways: bilateral nephrectomy, subcutaneous injections of a 0.5% aqueous solution of uranium nitrate at a rate of 5 mg per 1 kg of animal weight, or intravenous injections of a 1% aqueous solution of mercury chloride at a rate of 3 mg per 1 kg of animal weight. 87% of experimental animals developed necrotizing arteritis. Severe mural endocarditis was observed in the heart. Necrotizing arteritis developed only when animals were fed a diet rich in fat in combination with renal failure. Each of these factors individually did not cause significant damage to the vessel walls.
VASCULAR CHANGES ARISING FROM INSUFFICIENT AMOUNT OF PROTEIN IN FOOD
Hanmap (1951) gave white mice food with the following composition (in percentage): sucrose - 86.5, casein - 4, salt mixture - 4, vegetable oil - 3, fish oil - 2, cystine - 0, 5; anhydrous mixture of glucose - 0.25 (0.25 g of this mixture contained 1 mg of riboflavin), para-aminobezoic acid - 0.1, inositol - 0.1. To 100 g of diet, 3 mg of calcium pantothenate, 1 mg of nicotinic acid, 0.5 mg of thiamine hydrochloride and 0.5 mg of pyridoxine hydrochloride were added. The mice died within 4-10 weeks. Damage to the aorta, pulmonary artery and blood vessels of the heart, liver, pancreas, lungs and spleen was observed. At an early stage, a basophilic, homogeneous substance appeared in the intima of the vessels, forming plaques slightly protruding under the endothelium: focal damage to the medial membrane occurred with the destruction of elastic fibers. The process ended with the development of arteriosclerosis with the deposition of lime in areas of degeneration.
DYSTROPHIC-SCLEROTIC CHANGES IN VESSELS OBTAINED USING SOME CHEMICALS
(adrenaline, nicotine, tyramine, diphtheria toxin, nitrates, high molecular weight proteins)
Josue (1903) showed that after 16-20 intravenous injections of adrenaline, significant degenerative changes develop in rabbits, mainly in the middle tunic of the aorta, ending in sclerosis and, in some cases, aneurysmal dilatation. This observation was subsequently confirmed by many researchers. Erb (1905) injected rabbits into an ear vein every 2-3 days with 0.1-0.3 mg of adrenaline in a 1% solution; injections continued for several weeks and even months. Rzhenkhovsky (1904) injected rabbits intravenously with 3 drops of a solution of adrenaline 1: 1000; injections were made daily, sometimes at intervals of 2-3 days for 1.5-3 months. To obtain adrenaline sclerosis, B.D. Ivanovsky (1937) injected rabbits intravenously daily or every other day with a solution of adrenaline I: 20,000 in an amount of 1 to 2 ml. Rabbits received up to 98 injections. As a result of long-term injections of adrenaline, sclerotic changes naturally develop in the aorta and large vessels. It is mainly the middle shell that is affected, where focal necrosis develops, followed by the development of fibrosis and calcification of necrotic areas.
Ziegler (1905) observed in a number of cases thickening of the intima, sometimes significant. Aneurysmal enlargements of the aorta may occur. Areas of sclerosis and calcification become visible macroscopically after 16-20 injections. Significant sclerotic changes also develop in the renal (Erb), iliac, carotid (Ziegler) arteries and in the viutororgan branches of large arterial trunks (B.D. Ivanovsky). B.D. Ivanovsky showed that under the influence of repeated injections of adrenaline, significant changes occur in small arteries and even capillaries. The wall of the latter thickens, becomes sclerotic, and the capillaries are no longer adjacent, as normally, directly to the parenchymal elements of the organs, but are separated from them by a thin connective tissue layer.
Walter (1950), studying changes in blood vessels during the intravenous administration of adrenaline to dogs in large doses (8 ml of a solution of 1: 1000 every 3 days), showed that already within 10 days and even earlier, multiple hemorrhages were observed in the middle tunic of the thoracic aorta, and also in the small arteries of the heart, stomach, gall bladder, kidneys, and colon. There is fibrinoid necrosis of the tunica media and severe paparteritis with a perivascular cellular reaction. Preliminary administration of diabsiamin to animals prevents the development of these changes.
Davis and Uster (1952) showed that with a combination of intravenous injections of ep i e f r i a (25 mg per 1 kg of weight) and thyroxine (subcutaneous injection daily of 0.15 mg per 1 kg of weight) to rabbits, sclerotic changes in the aorta are especially pronounced. With daily subcutaneous injections of 500 mg of ascorbic acid into animals, the development of arteriosclerosis is noticeably delayed. Preliminary removal of the thyroid gland inhibits the development of arteriosclerosis caused by epinephrine (adrenaline). Dystrophic changes in the medial tunic of the aorta and large vessels with calcification and formation of cysts were observed by Huper (1944) in dogs that had experienced histamine in the cheek. Histamine was administered subcutaneously in a mixture with beeswax and mineral oil at the rate 15 mg per 1 kg of animal weight (see getting stomach ulcers with histamine).
Previously, Hooper and Lapsberg (1940) showed that in case of poisoning of dogs, er itol tetra nitrate O"m (administered orally for 32 weeks daily, in increasing doses from 0.00035 g to 0.064 g) or nitrogen acid With sodium (administered orally for several weeks, 0.4 g daily), pronounced dystrophic changes occur, mainly in the middle layer of the pulmonary artery and its branches. Significant lime deposits in some cases lead to a sharp narrowing. the lumen of the vessel, Huper (1944) observed the development of necrosis of the medial tunic of the aorta, followed by calcification and the formation of cysts in dogs, which were injected into the vein with a solution of methylcellulose in increasing quantities (from 40 to 130 ml) 5 times a week. The experiment continued for six months. .
Changes in the aorta similar to those described above can be obtained in animals with repeated injections of nicotin. A. 3. Kozdoba (1929) injected 1-2 ml of nicotine solution into the ear vein of rabbits daily for 76-250 days (average daily dose - 0.02-1.5 mg). Cardiac hypertrophy and dystrophic changes in the artery, accompanied by aneurysmal dilatation, were observed. All animals had significant enlargement of the adrenal glands. E. A. Zhebrovsky (1908) discovered necrosis of the medial tunic of the aorta with subsequent calcification and sclerosis in rabbits, which he placed daily for 6-8 hours under a hood filled with tobacco smoke. The experiments continued for 2-6 months. K. K. Maslova (1956) noted dystrophic changes in the aortic wall after daily intravenous injections of 0.2 ml of 1% nicotine solution into rabbits for 115 days. Bailey (1917) obtained pronounced dystrophic changes in the medial tunic of the aorta and large arteries with necrosis and multiple aneurysms with daily intravenous injections of 0.02-0.03 ml of diphtheric toxin into rabbits for 26 days.
Duff, Hamilton and Morgan (1939) observed the development of necrotizing arteritis in rabbits under the influence of repeated injections of tyramine (intravenous administration of 50-100 mg of the drug in the form of a 1% solution). The experiment lasted for 106 days. The majority of rabbits had pronounced changes in the aorta, large arteries and arterioles of the kidneys, heart and brain, and in each individual case the vessels of not all three organs, but one of them, were usually affected. In the aorta, necrosis of the middle membrane occurred, often quite significant; similar changes were found in the large vessels of the kidneys. In the heart, kidneys and brain, arteriolecrosis was observed, followed by hyalnosis of the vascular step. Some rabbits developed massive hemorrhage in the brain due to arteriolecrosis.
AORTITS OBTAINED BY MECHANICAL THERMAL AND INFECTIOUS DAMAGE OF THE VASCULAR WALL
In order to study the patterns of inflammatory and reparative processes in the aortic wall, some researchers use mechanical damage to the vessel. Prpor and Hartman (1956), after opening the abdominal cavity, cut off the aorta and damage the steica by piercing it with a thick needle with a sharp, curved end. Baldwin, Taylor and Hess (1950) damaged the aortic wall by short-term exposure to low temperature. To do this, the aorta is exposed in the abdominal section and a narrow tube is applied to the wall, into which carbon dioxide is injected. The aortic wall is frozen for 10-60 seconds. At the end of the second week after freezing, due to necrosis of the tunica media, an aortic aneurysm develops. In half of the cases, calcification of the damaged areas occurs. Metaplaetic formation of bone and cartilage often occurs. The latter appears no earlier than the fourth week after injury, and the bone appears after 8 weeks. A. Soloviev (1929) cauterized the wall of the aorta and carotid arteries with a hot thermal cautery. Schlichter (1946) To obtain aortic necrosis in dogs, he burned its wall with a burner. Pronounced changes in the inner lining (hemorrhages, necrosis) in some cases caused the rupture of the vessel. If this did not happen, sclerosis of the wall developed with calcification and the formation of small cavities. N. Andrievich (1901) injured the wall of the arteries by cauterizing it with a solution of silver nitrate; in some cases, after this, the affected segment was wrapped in celloidin, which, irritating the wall of the vessel, made the damage more significant.
Talquet (1902) obtained purulent inflammation of the vessel wall by introducing a staphylococcus culture into the surrounding tissue. Previously, Krok (1894) showed that purulent arteritis occurs when an animal is given an intravenous culture of microorganisms only if the vessel wall is first damaged. F.M. Khaletskaya (1937) studied the dynamics of the development of infectious aortitis, which develops as a result of the transition of the inflammatory process from the pleura to the aortic wall. A fistula tube was inserted into the pleural cavity of rabbits between the 6th and 7th ribs. The hole remained open for 3-5 days, and in some experiments for three months. After 3-5 days, fibrous-purulent pleurisy and pleural empyema developed. The transition of the process to the aortic wall was often observed. In the latter, necrosis of the middle shell initially occurred; they developed earlier than the inflammatory process spread to the aorta, and, in the opinion of F.M. Khaletskaya, were caused by vasomotor disorders due to intoxication (primary dystrophy and necrosis of the medial membrane). If suppuration spread to the aorta, the outer, middle and inner membranes were successively involved in the inflammatory process with the development of secondary necrotic changes.
Thus, the process ended with sclerosis of the vascular wall with the formation of small and large scars. Thromboarteritis was observed in the inner membrane, ending with thickening and sclerosis of the intima.
Literature:
Anichkov N.N. Beitr. pathol. Anat. u. allg. Pathol.. Bel 56, 1913.
Anichkov II.II. Verh. d. deutsch, pathol. Ges., 20:149, 1925.
Anichkov II.H. News, khpr. and Potrap, region, vol. 16--17 book 48--49 p. 105, 1929.
Anichkov II.P. Experimental studies on atherosclerosis. In the book: L. I. Abrikosov. Private pathologist, anatomy vol. 2 p. 378, 1947.
Valdez A.O. Arch. pathol., 5, 1951.
Walker F.I. Experimental data on phlebitis, thrombosis and embolism. Sat. works, pos.vyashch. 40th anniversary of the activity of V. N. Shevkunenko, L., 1937.
Vartapetov B.L. Doctor. case, 1. 4 3. 1941.
Vartapetov B.L. Doctor. case. 11 -- 12. 848, 1946.
Vinogradov S.A. Arch. pathologist, 2, 1950.
Vinogradov S.A. Arch. pathol., 1, 1955.
Vinogradov S.A. Bulletin exp. bpol. and med., 5, 1956.
Vishnevskaya O.II. All conf. pathologist Theses of the report, L. 1954.
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In 1912, N. N. Anichkov and S. S. Khalatov proposed a method for modeling atherosclerosis in rabbits by introducing cholesterol inside (through a tube or by mixing it with regular food). Pronounced atherosclerotic changes developed after several months with daily use of 0.5 - 0.1 g of cholesterol per 1 kg of body weight.
As a rule, they were accompanied by an increase in serum cholesterol levels (3-5 times compared to the initial level), which was the basis for the assumption of a leading pathogenetic role in the development of atherosclerosis-hypercholesterolemia. This model is easily reproducible not only in rabbits, but also in chickens, pigeons, monkeys, and pigs.
In dogs and rats resistant to the action of cholesterol, atherosclerosis is reproduced by the combined effect of cholesterol and methylthiouracil, which suppresses thyroid function. This combination of two factors (exogenous and endogenous) leads to prolonged and severe hypercholesterolemia (over 26 mmol/l - 100 mg%). Adding butter and bile salts to food also contributes to the development of atherosclerosis.
In chickens (roosters), experimental atherosclerosis of the aorta develops after long-term (4 - 5 months) exposure to diethylstilbestrol. In this case, atherosclerotic changes appear against the background of endogenous hypercholesterolemia, resulting from a violation of the hormonal regulation of metabolism.
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