Effects of Cholesterol and Cholesterol Esters on Cell Function I. Incorporation of Free Cholesterol and Cholesterol Oleate into the Cell Membrane and its Effects on Membrane Fluidity, Membrane Fragility and DNA Synthesis

The incorporation of cholesterol oleate and free cholesterol into the cells was observed by incubating them with the 14C-labeled compounds in vitro. Free cholesterol and cholesterol oleate were incorporated into the cytoplasmic membrane of Ehrlich ascites tumor cells (EATC) and human red blood cells (RBC). The oleate ester was taken up by cells faster than was free cholesterold. The resistance to osmotic hemolysis of RBC incubated with cholesterol oleate for 20 minutes increased but cells incubated with free cholesterol for the same period showed no increase in osmotic resistance. Cholesterol oleate strikingly suppressed FITC-Con A cap formation of EATC but free cholesterol had much less effect. Both free cholesterol and cholesterol oleate suppressed DNA synthesis or 3H-thymidine uptake of EATC, though the oleate ester had a much stronger effect than free cholesterol.