Accumulation and loss of cholesterol esters in monkey arterial smooth muscle cells exposed to normal and hyperlipemic serum lipoproteins.

The effects of high low and very low density lipoprotein fractions from normal or hyperlipemic rhesus monkey serum on the accumulation or removal of cholesterol esters from rhesus monkey smooth muscle cells in tissue culture were determined. Serum or serum lipoproteins were labeled with [14C] free cholesterol and adjusted to the same free cholesterol level in the incubation medium. Of the two normal lipoproteins examined, the LDL fraction caused more esterification than the HDL. Cells incubated in hyperlipemic serum showed a 2-fold stimulation in esterification as compared to cells in normal serum. This was contributed by hyperlipemic VLDL and LDL and led to a concomitant increase in cellular cholesterol ester content. Both hyperlipemic LDL and HDL stimulated esterification when compared to their normal counterparts. Cholesterol ester removal was examined by incubating the serum or lipoprotein fractions with cells enriched in cholesterol ester through a prior exposure to hyperlipemic serum. The cells incubated in normal or hyperlipemic HDL or lipoprotein-deficient serum had the lowest cholesterol ester content. Thus, the lipoprotein fractions which caused the lowest levels of cholesterol esterification were also the most efficient in the removal of cellular cholesterol esters.