title: Vasopressin increases expression of UT-A1, UT-A3, and ER chaperone GRP78 in the renal medulla of mice with a urinary concentrating defect.
abstract: Activation of V2 receptors (V2R) during antidiuresis increases the permeability of the inner medullary collecting duct to urea and water. Extracellular osmolality is elevated as the concentrating capacity of the kidney increases. Osmolality is known to contribute to the regulation of collecting duct water (aquaporin-2; AQP2) and urea transporter (UT-A1, UT-A3) regulation. AQP1KO mice are a concentrating mechanism knockout, a defect attributed to the loss of high interstitial osmolality. A V2R-specific agonist, deamino-8-D-arginine vasopressin (dDAVP), was infused into wild-type and AQP1KO mice for 7 days. UT-A1 mRNA and protein abundance were significantly increased in the medullas of wild-type and AQP1KO mice following dDAVP infusion. The mRNA and protein abundance of UT-A3, the basolateral urea transporter, was significantly increased by dDAVP in both wild-type and AQP1KO mice. Semiquantitative immunoblots revealed that dDAVP infusion induced a significant increase in the medullary expression of the endoplasmic reticulum (ER) chaperone GRP78. Immunofluorescence studies demonstrated that GRP78 expression colocalized with AQP2 in principal cells of the papillary tip of the renal medulla. Using immunohistochemistry and immunogold electron microscopy, we demonstrate that vasopressin induced a marked apical targeting of GRP78 in medullary principal cells. Urea-sensitive genes, GADD153 and ATF4 (components of the ER stress pathway), were significantly increased in AQP1KO mice by dDAVP infusion. These findings strongly support an important role of vasopressin in the activation of an ER stress response in renal collecting duct cells, in addition to its role in activating an increase in UT-A1 and UT-A3 abundance.
authors.affiliation: Dept. of Physiology, College of Medicine, Univ. of Arizona, Tucson, AZ 85724-5218, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Cai
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Nelson
authors.forename: Matthew R
authors.initials: MR
authors.lastname: McReynolds
authors.forename: Maggie Keck
authors.initials: MK
authors.lastname: Diamond-Stanic
authors.forename: David
authors.initials: D
authors.lastname: Elliott
authors.forename: Heddwen L
authors.initials: HL
authors.lastname: Brooks
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000235:genetics / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007671:Kidney Concentrating Ability / Q000235:genetics* / Q000502:physiology; D007679:Kidney Medulla / Q000187:drug effects* / Q000378:metabolism* / Q000503:physiopathology; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D009994:Osmolar Concentration; D012333:RNA, Messenger; D014667:Vasopressins / Q000494:pharmacology*; D000096982:Urea Transporters
chemical_list: D051398:Aquaporin 1; D003894:Deamino Arginine Vasopressin; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D014667:Vasopressins; D000096982:Urea Transporters; C496021:Aqp1 protein, mouse; C000717248:Hspa5 protein, mouse