Metabolism of cholesteryl esters of rat very low density lipoproteins

Abstract

Rat very low density lipoproteins (d<1.006), biologically labeled in esterified and free cholesterol, were obtained from serum 6 h after intravenous injection of particulate [3H]cholesterol. When injected into recipient animals, the esterified cholesterol was cleared from plasma with a half life of 5 min. After 15 min, 71% of the injected esterified [3H]cholesterol had been taken up by the liver, where it was rapidly hydrolyzed. After 60 min only 3.3% of the amount injected had been transferred, via lipoproteins of intermediate density, to the low density lipoproteins of plasma (d 1.019-1.063). Both uptake in the liver and transfer to low density lipoproteins occurred without change of distribution of 3H in the various cholesteryl esters. 3H appearing in esterified cholesterol of high density lipoproteins (d>1.063) was derived from esterification, presumably by lecithin:cholesterol acyltransferase, of simultaneously injected free [3H]cholesterol. Content of free [3H]cholesterol in the very low density lipoproteins used for injection could be reduced substantially by incubation with erythrocytes. This procedure, however, increased the rate of clearance of the lipoproteins after injection into recipient rats. These studies show that hepatic removal is the major catabolic pathway for cholesteryl esters of rat very low density lipoproteins and that transfer to low density lipoproteins occurs to only a minor extent.