11 alpha- and 11 beta-hydroxyprogesterone, potent inhibitors of 11 beta-hydroxysteroid dehydrogenase (isoforms 1 and 2), confer marked mineralocorticoid activity on corticosterone in the ADX rat.

The effects of 11 alpha- and 11 beta-hydroxyprogesterone (11 alpha-OHP, 11 beta-OHP), on the activity of the glucocorticoid inactivating enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) were studied. 11 alpha-OHP and 11 beta-OHP were potent inhibitors of both 11 beta-HSD1 in rat liver microsomes and 11 beta-HSD2 in lysates of JEG-3 cells, a human choriocarcinoma cell line. In addition, both progesterone metabolites were markedly potent in conferring mineralocorticoid activity upon B in the adrenalectomized rat. These results provide insight into the structural properties required of inhibitors of 11 beta-HSD activity and indicate a possible role for endogenous 11 beta-HSD inhibitors in the regulation of glucocorticoid-induced Na+ retention.