Effect of hyperlipemic serum lipoproteins on the lipid accumulation and cholesterol flux of rabbit aortic medial cells.

Abstract

<h2>Abstract</h2> The effects of hyperlipemic rabbit serum and its lipoproteins on the lipid accumulation in cultured rabbit aortic medial cells were evaluated in this study. Hyperlipemic serum stimulated the accumulation of cholesterol esters in these cells. Cells exposed to 5–40% normal serum had equivalent amounts of cholesterol ester, while cells exposed to only 2% hyperlipemic serum showed a 2–5-fold increase in cholesterol ester. This happened in spite of the fact that 2% hyperlipemic serum contained much less cholesterol than did 40% normal serum. Most of the cholesterol ester accumulation occurred in the initial 12 h and it could be reproduced by incubating these cells in a medium containing hyperlipemic low density lipoproteins. Cells exposed to low concentrations of hyperlipemic serum, as well as those in high concentrations of normal serum, also showed up to a 2-fold increase of free cholesterol and a smaller increase of triglycerides. This appeared to be a function of increased lipid level in the culture medium, not a specific effect of hyperlipemic serum. Furthermore, culture media containing a high lipid level, either from hyperlipemic serum or a high concentration of normal serum, showed a progressive increase in free cholesterol and a concomitant decline of cholesterol esters. These results indicated that the cells hydrolyzed a large amount of cholesterol ester. The present data do not permit a distinction to be drawn between hydrolysis in the cell and on the cell membrane. It is clear, however, that cells were required for hydrolysis and it is not due to enzymes excreted into the culture medium.