[Plasma lipoproteins and aortic collagen fractions in rabbits with different degrees of atherosclerosis].

Content of cholesterol and of collagen fractions (salt-, acid soluble and insoluble) in thoracal and peritoneal parts of aorta as well as concentration of products of collagen metabolism (protein-bound and free hydroxyproline) in blood plasma were studied in rabbits with various degree of atherosclerosis--separate lipid spots in aorta thoracal part (I group), total impairment of aorta (II group) and in control animals. Concentration of cholesterol and triglycerides was also studied in blood plasma and content of cholesterol, cholesterol and triglyceride esters, phospholipids and protein was measured in separate types of lipoproteins--lipoprotein of low (LPLD), of very low (LPVLD) and of high density (LPHD). Increase in content of cholesterol, salt-soluble and insoluble collagen from the both parts of aorta as well as in concentration of protein-bound and free hydroxyproline was found in rabbits of the II group as compared with the control animals. In animals of the I group content of collagen fractions in aorta was similar to that of control animals. Hypercholesterolemia, observed in both groups of rabbits, was most distinct in the II group, being related to the higher amount of cholesterol in LPLD fraction. The ratio of cholesterol esters, free cholesterol, triglycerides and phospholipids was similarly altered in LPVLD fraction of the groups of animals, mainly due to an increase in content of cholesterol esters. But rabbits of the I group were distinct from the II group of animals in the ratio of these components in LPLD: relative content of protein was lower and of cholesterol esters--higher in LPLD of the II group than of the I group. The data suggest that LPLD contained high amount of lipoproteins of intermediate density and cholesterol deposited into vessel wall from LPLD and lipoproteins of intermediate density at the increased rate. In LPHD from blood plasma of rabbits of the II group the ratios cholesterol/protein, cholesterol esters/protein as well as the molar ratio free cholesterol/phospholipids were increased; these data suggest that LPHD was saturated with cholesterol and LPHD appeared to lose the ability to eliminate cholesterol from the vessel wall. Differences in the degree of atherosclerotic impairments, existing between the I and II groups of animals, were apparently related to the variations in composition and content of lipoproteins, which regulate the level of cholesterol in vessel wall, as well as to content of collagen, i. e. they were due to features of metabolism of lipoproteins in blood plasma and of collagen in the vascular wall.