Effects of Regression of Atherosclerotic Lesions on the Content and Esterification of Cholesterol by Cell-Free Preparations of Pigeon Aorta

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Abstract
This study was designed to determine the effect of regression of atherosclerotic lesions on the incorporation of 1-14C-oleic acid into phospholipids, triglycerides, and cholesteryl esters and to compare these metabolic alterations with changes in the extent of atherosclerosis and the content of cholesterol and cholesteryl esters in the lesions. Aortic atherosclerosis was produced in White Carneau pigeons by feeding them an atherogenic diet for 1-8 months. The birds were then switched to a cholesterol-free diet for 6 months for the regression phase of the experiment. Following the regression phase, no changes were noted in the atherosclerotic index or the free-cholesterol content of aortas from pigeons that had received the atherogenic diet for 1-5 months; however, a reduction in both of these parameters was seen in aortas from pigeons fed the atherogenic diet for 8 months. There was a marked reduction in the content of cholesteryl esters in the aortas following the regression phase paralleled by a decrease in the rate of cholesterol esterification. No change was seen in the rate of incorporation of fatty acid into phospholipids or triglycerides. These studies suggest that local cholesterol esterification might be of considerable importance in maintaining the large amount of cholesteryl esters found in the atherosclerotic lesion and that changes in the rate of cholesterol esterification are associated with the early events in both progression and regression of atherosclerosis.