Increased cholesterol content and esterification in rabbit aortic medial cells cultured in hyperlipidemic serum

Cells of early atherosclerotic lesions have an increased content of cholesteryl esters and enhanced rate of cholesterol esterification. The present study was carried out to elucidate whether these changes could be reproduced in a purely in vitro system. Cultures of rabbit aortic medial cells were incubated in a medium containing 10% of either normal rabbit serum (control cells) or serum from rabbits with cholesterol-induced hyperlipidemia (hyperlipidemic cells). The incorporation rate of [1-14C]oleate into cellular cholesteryl esters increased two- to threefold after four hours' incubation with hyperlipidemic serum and remained elevated during the rest of the eight days' study. After seven days' incubation the hyperlipidemic cells incorporated significantly more (+13%) oleate into triglycerides and significantly less (-15%) oleate into phospholipids than did the control cells. Cholesteryl ester content of the hyperlipidemic cells rose steeply for about two days, with a slower rise thereafter. In hyperlipidemic cells the esterified cholesterol content was significantly higher (315 ng/mug DNA) than in the control cells (79 ng/mug DNA). Hyperlipidemic cells showed a slow but significant rise of free cholesterol as well (from 1.15 mug/mug DNA in control to 1.50 mug/mug DNA). The results indicate that lipid changes resembling those in early atherosclerotic lesions can be brought about in vitro 0y treatment of aortic cells with hyperlipidemic serum.