title: Vasopressin rapidly increases phosphorylation of UT-A1 urea transporter in rat IMCDs through PKA.
abstract: The UT-A1 urea transporter plays an important role in maintaining the hyperosmolar milieu of the inner medulla. Vasopressin increases urea permeability in rat terminal inner medullary collecting ducts (IMCDs) within 5-10 min. To elucidate the mechanism, IMCD suspensions were radiolabeled with [(32)P]orthophosphate. UT-A1 was immunoprecipitated and analyzed by autoradiogram and Western blot. Both the 97- and 117-kDa UT-A1 proteins were phosphorylated. Vasopressin treatment increased the phosphorylation of both UT-A1 proteins at 2 min, which peaked at 5-10 min and remained elevated for up to 30 min. There was a discernable increase in UT-A1 phosphorylation with 10 pM and a 50% increase with 10-100 nM vasopressin. 1-Desamino-8-D-arginine vasopressin (dDAVP) or 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) also increased UT-A1 phosphorylation. The vasopressin-stimulated increase in UT-A1 phosphorylation was blocked by H-89 or a specific peptide inhibitor of protein kinase A. Phosphatase inhibitors (okadaic acid, calyculin) increased UT-A1 phosphorylation. We conclude that vasopressin increases UT-A1 phosphorylation via protein kinase A within 2-5 min in rat IMCDs. This suggests that phosphorylation of UT-A1 may be the mechanism by which vasopressin rapidly increases urea permeability in vivo.
authors.affiliation: Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Chi
authors.initials: C
authors.lastname: Zhang
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Sands
authors.forename: Janet D
authors.initials: JD
authors.lastname: Klein
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007671:Kidney Concentrating Ability / Q000187:drug effects; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008387:Marine Toxins; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014508:Urea / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014667:Vasopressins / Q000494:pharmacology*; D000096982:Urea Transporters
chemical_list: D002352:Carrier Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D019319:Okadaic Acid; D010080:Oxazoles; D010749:Phosphoprotein Phosphatases; D014508:Urea; D014662:Vasoconstrictor Agents; D014667:Vasopressins; D000096982:Urea Transporters; C059041:calyculin A