title: Estradiol regulates AQP2 expression in the collecting duct: a novel inhibitory role for estrogen receptor α.
abstract: While there is evidence that sex hormones influence multiple systems involved in salt and water homeostasis, the question of whether sex hormones regulate aquaporin-2 (AQP2) and thus water handling by the collecting duct has been largely ignored. Accordingly, the present study investigated AQP2 expression, localization and renal water handling in intact and ovariectomized (OVX) female rats, with and without estradiol or progesterone replacement. OVX resulted in a significant increase in urine osmolality and increase in p256-AQP2 in the renal cortex at 7 days post-OVX, as well as induced body weight changes. Relative to OVX alone, estradiol repletion produced a significant increase in urine output, normalized urinary osmolality and reduced both total AQP2 (protein and mRNA) and p256-AQP2 expression, whereas progesterone repletion had little effect. Direct effects of estradiol on AQP2 mRNA and protein levels were further tested in vitro using the mpkCCD principal cell line. Estradiol treatment of mpkCCD cells reduced AQP2 at both the mRNA and protein level in the absence of deamino-8-d-AVP (dDAVP) and significantly blunted the dDAVP-induced increase in AQP2 at the protein level only. We determined that mpkCCD and native mouse collecting ducts express both estrogen receptor (ER)α and ERβ and that female mice lacking ERα displayed significant increases in AQP2 protein compared with wild-type littermates, implicating ERα in mediating the inhibitory effect of estradiol on AQP2 expression. These findings suggest that changes in estradiol levels, such as during menopause or following reproductive surgeries, may contribute to dysregulation of water homeostasis in women.
authors.affiliation: Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark;
authors.forename: Muhammad Umar
authors.initials: MU
authors.lastname: Cheema
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska; and.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Irsik
authors.affiliation: Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark;
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark;
authors.forename: William
authors.initials: W
authors.lastname: Miller-Little
authors.affiliation: Division of Nephrology, University of Alabama at Birmingham, Birmingham, Alabama.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Hyndman
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska; and.
authors.forename: Eileen S
authors.initials: ES
authors.lastname: Marks
authors.affiliation: Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark;
authors.forename: Jørgen
authors.initials: J
authors.lastname: Frøkiær
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska; and.
authors.forename: Erika I
authors.initials: EI
authors.lastname: Boesen
authors.affiliation: Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark; rn@clin.au.dk.
authors.forename: Rikke
authors.initials: R
authors.lastname: Norregaard
mesh_terms: D000818:Animals; D051399:Aquaporin 2 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000819:agonists* / Q000172:deficiency / Q000235:genetics; D015914:Estrogen Replacement Therapy; D005260:Female; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009994:Osmolar Concentration; D064587:Osmoregulation / Q000187:drug effects*; D010052:Ovariectomy; D010766:Phosphorylation; D011374:Progesterone / Q000494:pharmacology; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D017208:Rats, Wistar; D013997:Time Factors; D014554:Urination / Q000187:drug effects; D015430:Weight Gain / Q000187:drug effects
chemical_list: C496023:AQP2 protein, human; C496025:Aqp2 protein, rat; D051399:Aquaporin 2; D047628:Estrogen Receptor alpha; D012333:RNA, Messenger; D011374:Progesterone; D004958:Estradiol
keywords: AQP2; ERα; KO mice; estrogen