The esterification of cholesterol in vitro by rat plasma

Abstract

The synthesis of cholesterol esters by plasma and extracts of acetone powders of rat plasma was studied with the following substrates: (a) lecithin labeled in the β position with either [I-¹⁴C]oleic acid, [I-¹⁴C]linoleic acid or [I-¹⁴C]palmitic acid; (b) trigylcerides labeled with either [I-¹⁴C]palmitic acid or [I-¹⁴]oleic acid; (c) [4-¹⁴C]cholesterol. As much as 24 and 50% of the incubated ¹⁴C was recovered as cholesterol esters when the labeled lecithins and free cholesterol, respectively, were incubated, and less than I% was so recovered when the labeled trigylcerides served as substrates. Snake venom completely prevented the formation of labeled cholesterol esters by acetone powder extracts in the experiments with fatty acid-labelled lecithin and the labeled free cholesterol. These findings support the hypothesis that the esterification of cholesterol is brought about by a fatty acid transferase and, in addition, suggest that the transesterification is limited to fatty acidss on the β position of phospholipids, regardless of the nature of the fatty acids, this being an intermediatry step even in the transesterification from trigylcerides.