Movement of Labeled Cholesterol Between Plasma Lipoprotein and Normal Arterial Wall across the Intimal Surface

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Abstract
Normal rat aortas were incubated with their intimal surfaces in contact with a lipoprotein solution containing isotopically labeled free cholesterol. Uptake of cholesterol by the tissue increased with increasing concentration toward a plateau level. Maximum uptake of free cholesterol was estimated to be 13 µg/cm2 per 24 hours, and uptake at physiological cholesterol concentration was 7.9 µg/cm2 per 24 hours. Aortas containing labeled cholesterol were prepared by intragastric administration of cholesterol-7α-3H to normal rats. Experiments in vitro with these aortas demonstrated that efflux across the intimal surface was dependent upon presence of lipoprotein in the medium. This efflux was not retarded by prior boiling of the tissue. These results support suggestions that movement of labeled free cholesterol from plasma into the arterial wall may be largely the result of a physicochemical exchange between lipoprotein and endothelium.