Entry of esterified cholesterol into foam cells

A mixture of doubly labelled cholesterol linolenate and non-radioactive cholesterollinoleate was injected subcutaneously in rats. The lipid implants were separated into predominantly extracellular and intracellular phases by progressive solvent extractions. Chromatography and scintillation counting of the fractions showed that little esterified cholesterol had been hydrolysed in the intracellular phase and little randomization of fatty acids had occurred between radioactive and non-radioactive cholesterol. It is concluded that foam cells (macrophages) can take up cholesterol in esterified form and that preliminary hydrolysis to free cholesterol is not obligatory for uptake by these cells.