Possible endogenous regulators of steroid inactivating enzymes and glucocorticoid-induced Na+ retention

Various endogenous substances which bear similar structural resemblances to glycyrrhetininc acid were screened for inhibitory activity against 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) and 5 beta-reductase (5 beta-R). Among the compounds screened, 3 alpha, 5 beta-tetrahydroprogesterone (3 alpha,5 beta-THP) was a potent inhibitor of 11 beta-OHSD and a moderate inhibitor of 5 beta-R. Of the bile acids tested, chenodeoxycholic acid (CDCA) was the most potent inhibitor of both 11 beta-OHSD and 5 beta-R. Cholic acid (CA), a moderate inhibitor of 11 beta-OHSD was a weak inhibitor of 5 beta-R, whereas deoxycholic acid was a moderate inhibitor of 5 beta-R but a weak inhibitor of 11 beta-OHSD. 3 alpha, 5 beta-THP and bile acids were also tested to determine whether, like GA, they could confer mineralocorticoid actions upon corticosterone (B). In adrenalectomized rats pretreated with CDCA or 3 alpha,5 beta-THP, B caused a significant antinatriuresis; the effect of B plus CDCA was blocked by the antimineralocorticoid, RU 28318. Thus, we report on two structurally similar endogenous substances, 3 alpha, 5 beta-THP and CDCA, which inhibit both 11 beta-OHSD and 5 beta-R activity, and which can confer mineralocorticoid actions upon the glucocorticoid, B.