Metabolism of 25-hydroxycholesterol in mammalian cell cultures. Side-chain scission to pregnenolone in mouse L929 fibroblasts.

Three mammalian cell lines were examined for their ability to metabolize the regulatory oxysterol, 25-hydroxycholesterol, and derepress 3-hydroxy-3-methylglutaryl CoA reductase. In mouse L cell fibroblasts reductase activity was restored with the concomitant metabolism of 25-hydroxycholesterol via side-chain hydroxylation and scission of the C20-C22 bond. Chinese hamster lung cells did not appear to derepress the reductase and these cells and Chinese hamster ovary cells did not metabolize 25-hydroxycholesterol to a significant extent. Only 5-10% of the oxysterol became esterified with a fatty acid in any of the cell lines when grown in the described culture conditions.