Comparison of cholesteryl ester transfer from chylomicrons and other plasma lipoproteins to aortic intima media of cholesterol-fed rabbits

Abstract

Lymph chylomicrons labeled with 14C-cholesterol and plasma very low and intermediate density lipoproteins (d less than 1.019) labeled with 3H-cholesterol were injected simultaneously into recipient cholesterol-fed rabbits. The cholesteryl ester of chylomicron origin (14C) found in the tissues 1 to 4 hours after the injection is the sum of both direct and indirect uptake of chylomicron cholesteryl ester. The direct uptake of chylomicron cholesteryl ester is defined as occurring in situ during the interaction between chylomicrons and lipoprotein lipase in endothelial cells. The indirect uptake of chylomicron cholesteryl ester results from the uptake of chylomicron remnants and of other plasma lipoproteins which become labeled during the degradation of the injected chylomicrons by net lipid transfer or by exchange. The indirect contribution of chylomicron cholesteryl ester to tissues was calculated from tissue 3H-cholesteryl ester derived from injected plasma d less than 1.019 lipoproteins. In rabbits fed 0.5 g cholesterol daily for 40-60 days, with plasma cholesterol concentrations between 20 and 30 mM (800-1200 mg/dl), less than 1% of the cholesteryl ester influx into aortic intima media and less than 10% in liver was derived from the direct uptake of chylomicron cholesteryl ester.