Oxysterols in cultured bovine aortic smooth muscle cells and in the monocyte-like cell line U937.

Oxysterols in cultured bovine aortic smooth muscle cells and in the monocyte-like cell line U937 were analyzed by gas-liquid chromatography. The following products were detected: 7 alpha- and 7 beta-hydroxycholesterol, 7-ketocholesterol, cholesterol-alpha-epoxide, cholesterol-beta-epoxide, cholestanetriol, and 20- and 25-hydroxycholesterol. The proportions of oxidized cholesterol varied from 1 to 3% of total cholesterol. The concentrations of oxysterols were lower when the smooth muscle cells were maintained in a vitamin E-enriched medium, and were higher in U937 cells when the cells were activated with phorbol myristate acetate. The cell oxysterol content appears to be regulated by factors that inhibit or enhance free radical generation. The concentrations of oxysterols found in cells may serve as an indicator of the extent of lipid peroxidation.