Effects of 22S-hydroxy-cholesterol and other hydroxylated sterols on the ACTH-stimulated steroid production in rat adrenal cells.

Several effects of hydroxylated sterols on cell cultures are known. Most of these can be explained by an inhibition of the cholesterol synthesis at the level of the 3-hydroxy-3-methylglutaryl CoA reductase. When studying cholesterol metabolism in rat adrenal cells, an inhibitory action of some sterols on the ACTH-stimulated corticosterone production was observed. The effects of one sterol, 22S-OH-cholesterol, were investigated further. The sterol had no effect on the ACTH-stimulated cyclic AMP production, suggesting an intact receptor-adenylate cyclase complex and cellular membrane. In the presence of ACTH and 22-OH-cholesterol particularly the free cholesterol concentration was elevated; 22S-OH-cholesterol therefore probably exerts its inhibitory effect at a step located after hydrolysis of the cholesterol esters. 22S-OH-cholesterol had no effect on the conversion of exogenous pregnenolone into corticosterone. These results make it probable, that the inhibitory effect of 22S-OH-cholesterol on the ACTH-stimulated corticosterone production is situated at the level of the cholesterol side-chain cleavage.