The deposition of lipids from serum into cells cultured in vitro

The deposition of lipid into a line of fibroblasts cultured in vitro was studied. When cells were transferred from a low lipid serum to high lipid serum prepared from a cholesterol fed rabbit, an increased amount of lipid was deposited within the cells. An increase in all major classes of lipid was observed. Particularly striking, however, was the increase in the amount of cholesterol esters relative to cholesterol during growth in lipemic serum. The source of the major part of this lipid was the serum of the medium, less than 6% arising from de novo synthesis. In normal serum 80% of the radioactivity incorporated into neutral cell lipids from [1- 14C]acetate was recovered in cholesterol, only 7% in cholesterol esters and 8% in triglycerides. In lipemic serum only 3% was recovered in cholesterol whereas 65% was recovered in cholesterol esters and 25% in triglycerides.