title: 11beta-hydroxyprogesterone acts as a mineralocorticoid agonist in stimulating Na+ absorption in mammalian principal cortical collecting duct cells.
abstract: The binding of mineralocorticoid hormones to the mineralocorticoid receptor is the first step in a cascade of events leading to the stimulation of Na(+) reabsorption by renal cortical collecting duct (CCD) principal cells. The agonist properties of mineralocorticoid hormones are linked to contacts between their 21-hydroxyl group and Asn770, a residue of the ligand-binding domain of the human mineralocorticoid receptor (hMR). Here, we investigate whether the presence of a hydroxyl group at position 11, 17, or 20 could also alter the activity of progesterone (P), a mineralocorticoid antagonist without the 21-hydroxyl group. Both 17 alpha-hydroxyprogesterone (17OHP) and 20 alpha-hydroxyprogesterone (20OHP) antagonized the aldosterone-induced trans-activation activity (IC(50): 17OHP, 10(-7) M; 20OHP, 10(-8) M) of the hMR transiently expressed in COS-7 cells lacking steroid receptors. In cultured mouse mpkCCD(cl4) principal cells, 17OHP and 20OHP also prevented the aldosterone-stimulated amiloride-sensitive component of the short-circuit current (Ams I(sc)), reflecting Na(+) absorption mediated by the epithelial Na(+) channel (ENaC). In contrast, 11 beta-hydroxyprogesterone (11OHP) activated the transiently expressed hMR in COS-7 cells in a dose-dependent manner (ED(50): 10(-8) M) and, like aldosterone, stimulated Ams I(sc) in mpkCCD(cl4) cells. Docking 11OHP within the hMR-ligand-binding domain homology model revealed that the agonist activity of 11OHP is caused by contacts between its 11 beta-hydroxyl group and Asn770. Furthermore, 11OHP was unable to activate the mutant hMR/N770A, in which Ala is substituted for Asn at position 770. These findings demonstrate that in the absence of the 21-hydroxyl group, the 11 beta-hydroxyl group can produce the contact with the hMR-Asn770 required for the hMR activation leading to stimulated Na(+) absorption.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U478, Institut Fédératif de Recherche 02, Faculté de Médecine Xavier Bichat, Paris, France. oblin@bichat.inserm.fr
authors.forename: Marie-Edith
authors.initials: ME
authors.lastname: Rafestin-Oblin
authors.forename: Jerome
authors.initials: J
authors.lastname: Fagart
authors.forename: Anny
authors.initials: A
authors.lastname: Souque
authors.forename: Cendrine
authors.initials: C
authors.lastname: Seguin
authors.forename: Marcelle
authors.initials: M
authors.lastname: Bens
authors.forename: Alain
authors.initials: A
authors.lastname: Vandewalle
mesh_terms: D000042:Absorption / Q000187:drug effects; D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002474:Cell-Free System; D002522:Chlorocebus aethiops; D006801:Humans; D006908:Hydroxyprogesterones / Q000494:pharmacology*; D007685:Kidney Tubules, Collecting / Q000166:cytology*; D051379:Mice; D011188:Potassium / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology; D018161:Receptors, Mineralocorticoid / Q000819:agonists* / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D006908:Hydroxyprogesterones; D018161:Receptors, Mineralocorticoid; D000450:Aldosterone; D011374:Progesterone; D011188:Potassium