Differential uptake of cholesterol and of different cholesterol esters by atherosclerotic intima in vivo and in vitro

Abstract

Cholesterol-fed rabbits were intubated with a single dose of [ 3H]cholesterol and the entry of the resultant labelled free cholesterol, cholesterol ester and of the individual cholesterol esters in the serum into the aortic intima and media was determined 4 days after ingestion of the cholesterol. The entry of cholesterol into the aortic intima exceeded that of cholesterol ester; the entry of monounsaturated cholesterol ester exceeded that of polyunsaturated cholesterol ester. The greater entry of cholesterol relative to cholesterol ester was confirmed in experiments in vitro in which atherosclerotic aortas were incubated with hypercholesterolaemic serum labelled with [ 3H]cholesterol ester and 3H 14C-labelled free cholesterol in the lipoprotein. It was not possible, however, to demonstrate any significant increase in entry of monounsaturated cholesterol ester over polyunsaturated cholesterol ester in these experiments in vitro. By using hypercholesterolaemic serum containing [ 3H]cholesterol ester and 3H 14C-labelled free cholesterol in the lipoprotein, as incubation medium, it was possible to demonstrate in the experiments in vitro that hydrolysis of the labelled cholesterol ester entering the intima could not account for the greater relative influx of free over ester cholesterol. The factors associated with the entry and accumulation of cholesterol and of various cholesterol esters in the atherosclerotic lesion are discussed.