SOURCE OF THE CHOLESTEROL ESTER ACCUMULATED IN MONKEY ARTERIAL SMOOTH-MUSCLE CELLS GROWN IN HYPERLIPEMIC SERUM

The author studied various sources of cellular cholesterol ester to determine the origin of the esters that accumulated in monkey smooth muscle cells exposed to hyperlipemic serum. The movement of free cholesterol between the serum and the cells and its esterification by the smooth muscle cells were followed by means of a double-label procedure. Both uptake and efflux of free cholesterol were nearly linear over a 40-hour period. Approximately one-third of the total cellular cholesterol ester was derived from the esterification of free cholesterol taken up from the hyperlipemic serum in the medium, and one-third originated from the esterification of the free cholesterol poresent in the cells at zero time. Cholesterol esters of the hyperlipemic serum accounted for the major portion of the final third. The contribution to cellular cholesterol ester by cholesterol synthesized de novo by the cells was minimal. Maximal cellular cholesterol ester levels were achieved in the smooth muscle cells after 2 days of incubation in hyperlipemic serum, and additional repeated exposures to this serum produced little further ester accumulation. The results suggest that cellular esterification of free cholesterol may be of major importance to the increase in the cholesterol ester content of arterial cells exposed to hyperlipemic serum, since this process provided at least 60% of the total cholesterol esters accumulated.