Molecular mechanisms of urea transport.
Physiologic data provided evidence for specific urea transporter proteins in red blood cells and kidney inner medulla. During the past decade, molecular approaches resulted in the cloning of several urea transporter cDNA isoforms derived from two gene families: UT-A and UT-B. Polyclonal antibodies were generated to the cloned urea transporter proteins, and their use in integrative animal studies resulted in several novel findings, including: (1) UT-B is the Kidd blood group antigen; (2) UT-B is also expressed in many non-renal tissues and endothelial cells; (3) vasopressin increases UT-A1 phosphorylation in rat inner medullary collecting duct; (4) the surprising finding that UT-A1 protein abundance and urea transport are increased in the inner medulla during conditions in which urine concentrating ability is reduced; and (5) UT-A protein abundance is increased in uremia in both liver and heart. This review will summarize the knowledge gained from studying molecular mechanisms of urea transport and from integrative studies into urea transporter protein regulation.
Sands
J M
JM
Renal Division, Department of Medicine and Department of Physiology, Emory University School of Medicine, 1639 Pierce Dr., NE, Atlanta, GA 30322, USA. jsands@emory.edu
D000809:Angiotensins / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability / Q000187:drug effects; D003920:Diabetes Mellitus / Q000503:physiopathology; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000502:physiology; D007671:Kidney Concentrating Ability / Q000187:drug effects / Q000502:physiology; D007679:Kidney Medulla / Q000187:drug effects / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D051381:Rats; D051437:Renal Insufficiency / Q000503:physiopathology; D014508:Urea / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics*; D014511:Uremia / Q000503:physiopathology; D014556:Urine; D014667:Vasopressins / Q000494:pharmacology; D000096982:Urea Transporters
D000809:Angiotensins; D026901:Membrane Transport Proteins; D014508:Urea; D014667:Vasopressins; D000096982:Urea Transporters