Separation and quantitation of free cholesterol and cholesteryl esters in a macrophage cell line by high-performance liquid chromatography.

A method for the direct high-performance liquid chromatographic (HPLC) determination of free cholesterol and the individual cholesteryl esters in cell culture experiments is described. The murine macrophage-like J774 cell line was loaded with cholesterol by incubation with low-density lipoproteins. After extraction of the cellular lipids with hexane-isopropanol (3:2, v/v), the cholesteryl esters were identified and quantified by isocratic HPLC. Unesterified cholesterol and its esters were eluted with acetonitrile-isopropanol (50:50, v/v) on a Zorbax ODS column within 25 min and detected at 210 nm. Cholesteryl heptadecanoate was used as an internal standard. The detection response is linear in the analytical range of interest; the overall coefficients of variation are less than 8% and the detection limit is between 50 and 150 ng. The results demonstrate that HPLC is suitable for the determination of cellular cholesteryl ester profiles and could usefully contribute to the understanding of the mechanism of foam cell formation during the development of atherosclerosis. This method can also be applied to all experimental systems involving the study of cholesteryl esters.