Influence of Duration of Cholesterol Feeding on Esterification of Fatty Acids by Cell-Free Preparation of Pigeon Aorta STUDIES ON THE MECHANISM OF CHOLESTEROL ESTERIFICATION

Influence of duration of cholesterol feeding on esterification of fatty acids and hydrolysis of cholesteryl esters was studied in cell-free preparations of aorta from White Cameau pigeons. Esterification of fatty acids required ATP and CoA; greater than 80* of the esterifying activity was located in the particulate fraction obtained by centrifugation at 105,000 X g (after a preliminary centrifugarion at 1000 X g) . Fatty acids were incorporated most efficiently into phospholipid, primarily (82%) lecithin. Greater than 87% of the fatty acid was esterified at the 2-position. During 8 months of cholesterol feeding, incorporation of oleic acid into phospholipids and triglycerides increased relatively little (less than double that of controls); no changes were seen before 1 month. Esterification of oleic acid to cholesterol was increased after 2 weeks of cholesterol feeding (before gross lesions were seen), eventually reaching a maximum increase of 30to 50-fold. Cholesterol was esterified by transfer of fatty acyl-CoA to cholesterol, a mechanism similar to that described for liver and adrenal cortex. Little if any cholesterol esterification occurred when lecithin labeled at the 2-position with oleic acid-l-C was used as substrate. The relationship between duration of cholesterol feeding and hydrolysis of cholesteryl oleate could not be evaluated since results depend directly on an unknown extent of equilibration of substrate with pre-existing cholesteryl ester pools. ADDITIONAL