[Mechanism of lipoprotein and cholesterol transport into the vascular wall]

Penetration of radioactive lipoproteins of very low and low density, of free cholesterol and its esters into the aortal wall of rabbits was studied. Close values for ratios between lipids and protein, cholesterol and esterified cholesterol contained in the perfusate's lipoproteins and corresponding lipoprotein fractions separated from normal and atherosclerotic aortas following their perfusion were registered. These findings bear evidence to the fact of atherogenic lipoproteins penetrate the vascular wall in the form of intact particles. Quantitative regularities educed in this connection point to a greater permeability of atherosclerotic aortas to lipoproteins. An analysis of aortal lipids uncombined with lipoproteins showed the ratio between cholesterol and etherified cholesterol to be on the average 5.5 times as high as in the lipoproteins of the aorta and the perfusate. The prevalence of cholesterol in the lipids of the aortal tissue uncombined with lipoproteins points to the existence of other mechanisms governing the entrance of radioactive cholesterol into the vascular wall. Tests in vivo involving intravenous administration of C14-cholesterol yielded the same regularities as "in vitro" experiments.