title: Effects in vitro of medroxyprogesterone acetate on steroid metabolizing enzymes in the rat: selective inhibition of 3 alpha-hydroxysteroid oxidoreductase activity.
abstract: The effects of 6 alpha-methyl-17 alpha-acetoxy-4-pregnene 3,20-dione (MPA) on the activity of different steroid metabolizing enzymes in vitro were investigated in several organs in the rat. MPA seems to be a potent inhibitor of 3 alpha-reduction of 17 beta-hydroxy-5 alpha-androstan-3-one (Dht) in homogenates of the testis, ovary, epididymis, prostate, kidney and the adrenal glands. In testicular homogenates MPA acts like a competitive inhibitor of the 3 alpha-reduction of Dht, with Ki of 0.42 [microM]. MPA seems to be a selective inhibitor of 3 alpha-hydroxysteroid oxidoreductase in numerous organs. Steroid metabolizing enzymes like 5 alpha-reductase, 7 alpha-hydroxylase, 3 beta-hydroxysteroid oxidoreductase and 17 beta-hydroxysteroid oxidoreductase were not inhibited by MPA under the conditions of incubation employed in these studies.
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D015096:3-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D003271:Contraceptive Agents, Female / Q000494:pharmacology*; D004822:Epididymis / Q000201:enzymology; D005260:Female; D007668:Kidney / Q000201:enzymology; D008297:Male; D008525:Medroxyprogesterone / Q000031:analogs & derivatives* / Q000494:pharmacology; D017258:Medroxyprogesterone Acetate; D010053:Ovary / Q000201:enzymology*; D011467:Prostate / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D013737:Testis / Q000201:enzymology*
chemical_list: D003271:Contraceptive Agents, Female; D017258:Medroxyprogesterone Acetate; D015067:17-Hydroxysteroid Dehydrogenases; D015096:3-Hydroxysteroid Dehydrogenases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D008525:Medroxyprogesterone