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Intravenous ethyl oleate-induced blockade of the reticulo-endothelial apparatus (REA) in rabbits was found to reduce the elimination rate of both native and 125I-modified (acetylated) low lipoproteins. Lower lipoprotein catabolism is likely to result in hyperlipidemia observed in REA blockade. At the same time the latter was shown to induce the changes in low lipoproteins, which diminished their capacity to interact with fibroblasts, on the one hand, and to stimulate their macrophage uptake.

The level of lipids and apolipoproteins was studied in the serum of patients with various degrees of obesity without hormonal impairments in order to find interrelationship between obesity and atherosclerosis development. 14 men and 42 women aged 19-59 years were examined. Concentration of triglycerides and very low density lipoprotein (VLDL) cholesterol was distinctly higher in obese patients of both sexes than in normal weight persons. However, content of apo A-I and apo B was similar in blood of both obese and normal persons, while concentration of apo E was higher in obesity. In obesity, the ratio HDL cholesterol/A-I was decreased, thus indicating that the HDL3/HDL2 ratio was altered, showing a decreased content of the latter subfraction. The findings suggest that impairment in metabolism of mainly HDL and VLDL subfractions occurred in patients with obesity. These impairments were atherogenic and may be responsible for a high risk for atherosclerosis and heart ischemic disease in obese patients.

Interaction of cholesterol with apoproteins A-I and E was studied in absence of phospholipids in vitro. As shown by two methods - ultracentrifugation in density gradient of KBr and an extraction technique - an apoprotein E molecule bound 30-35 molecules of cholesterol and a molecule of A-I bound 17-22 molecules of the sterol. If the primary structure of apoprotein A-I and the fragments of apoprotein E are involved in consideration, the hydrophilic reaction appears to occur between the hydroxyl group of cholesterol and a guanidine group of the protein arginine residues as well as hydrophobic reaction - between side aliphatic chain of the sterol and the branched-chain amino acid, present in the protein at a distance of 4 amino acid residues from the arginine residue. A molecular model, illustrating the cholesterol reaction with polypeptide fragments, is developed. Considering high alpha-spirality of apoproteins E and A-I with specific localization of the charged residues, reaction of the sterol and apoproteins, described in the terms of this model, was possible only after a decrease in order of the protein structure. Dispersion spectra and optical rotation of apoprotein E showed that beta-structures were destroyed and alpha-spiralization was decreased in the protein in presence of cholesterol. The data obtained suggest that amino acid composition and structure of polypeptides are important for their reaction with cholesterol.

In men with increase of age from senile to longevity content of total cholesterol was practically unaltered (182 and 184 mg/100 ml), concentration of cholesterol in LPHD was increased from 52 mg up to 58.3 mg/100 ml simultaneously with unaltered content of LPLD cholesterol (102 mg/100 ml) and of LPVLD cholesterol (27.1 and 27 mg/100 ml). Triglycerides decreased from 136 mg down to 101 mg/100 ml. In women content of total blood cholesterol was about 218 mg/100 ml in senile age and 204 mg/100 ml in longevity and concentration of LPHD cholesterol--61 mg and 64.6 mg/100 ml, respectively. Contrary to men, in women a distinct decrease in content of LPLD cholesterol (from 127 mg to 110 mg/100 ml) as well as of triglycerides (from 154 to 145 mg/100 ml) were found on transition from senile age to longevity. Concentration of the apolipoproteins studied was unaltered in men on transition from senile age to longevity and in women concentration of apolipoprotein A-I decreased from 143 mg to 130 mg/100 ml and of apo-E from 11.1 mg to 9.2 mg/100 ml. The decrease in LPLD cholesterol content and increase of LPHD cholesterol, simultaneously with relatively low content of total blood cholesterol, appear to be considered among the reasons responsible for longevity and lesser risk of heart ischemic disease.

Content of apo A-I constitute 136 mg/100 ml, of apo A-II--64 mg/100 ml and of apo E--10 mg/100 ml in blood plasma of 20--60 years old men with normal concentration of cholesterol (alpha-CS) in blood. In the patients with hyper-alpha-lipoproteinemia (alpha-CS was above 76 mg per 100 ml) concentrations of apo A-I and apo A-II were distinctly higher (173 and 71 mg per 100 ml, respectively) and that of apo E--was lower (8 mg per 100 ml) as compared with the healthy persons. Under the conditions of hypo-alpha-lipoproteinemia (alpha-CS was below 37 mg per 100 ml) the contents of apo A-I and apo A-II were decreased down to 116 and 50 mg per 100 ml, respectively, and that of apo E--increased up to 12 mg per 100 ml. Concentration of the total fraction of high density lipoproteins (LPHD), LPHD2 and their subfraction LPHD2a and LPHD2b was also distinctly increased in hyper-alpha-lipoproteinemia; it was decreased in hypo-alpha-lipoproteinemia, while the LPHD3 content was slightly altered in blood plasma. The capacity of LPHD to transfer of CS appears to increase in hyper-alpha-lipoproteinemia and to decrease in hypo-alpha-lipoproteinemia. As shown by correlation analysis, metabolism of LPHD3 occurred independently from the other LPHD subfractions.

Rabbit mesenteric lymph contained all the main classes of lipoproteins detected in plasma: chylomicrons (CM), very low density lipoproteins (VLDL), low density lipoproteins (LDL), high density lipoproteins (HDL). The main classes of lipoproteins in lymph were CM and VLDL, whereas LDL and HDL were the main lipoproteins in blood plasma. The heaviest subfractions HDL3 were not observed in mesenteric lymph. Lymph contained only low amount of LDL; molecular mass of lymphatic LDL was lower as compared with the blood plasma lipoproteins. Mesenteric lymph lipoproteins were enriched with triglycerides and contained less cholesterol, phospholipids and protein than the corresponding blood plasma lipoproteins. As distinct from blood plasma lipoproteins, apo E and apoproteins of low molecular mass (apo C?) were not found in lymphatic lipoproteins. Content of Apo-I was much higher in lymphatic VLDL as compared with the blood plasma VLDL. The dissimilarity in patterns and composition between blood plasma and lymphatic lipoproteins indicated that the latter were derived from intestine. Thus, intestine was able to produce CM, VLDL, HDL2 and apparently a small amount of LDL.

Effect of taurine o binding of 45Ca2+ and 8-aniline-I-naphthaline culfonate by microsomes of rat brain cells was studied. Increased accumulation of Ca2+ in phospholipids of microsomes as well as a distinct decrease in the number of sites for binding of 8-aniline-I-naphthaline sulfonate were observed in presence of taurine. Activity of Ca2+-ATPase was simultaneously increased. The data obtained suggest that the effect of taurine on biomembranes is related to local alterations in their surface charge.

An immune complex of lipoprotein-antibody was found in human blood plasma and in tissue liquid of aorta, impaired by atherosclerosis. In the majority of cases the antigen component of the immune complex was lipoprotein of very low density. After dissociation of the complex at acid pH, immunoglobulin G was isolated, which was identified by double immunodiffusion in agar gel; the immunoglobulin reacted in RBS both with autological and, in some cases, with isological lipoproteins.