Molecular approaches to urea transporters.
Urea plays a critical role in the urine-concentrating mechanism in the inner medulla. Physiologic data provided evidence that urea transport in red blood cells and kidney inner medulla was mediated by specific urea transporter proteins. Molecular approaches during the past decade resulted in the cloning of two gene families for facilitated urea transporters, UT-A and UT-B, encoding several urea transporter cDNA isoforms in humans, rodents, and several nonmammalian species. Polyclonal antibodies have been generated to the cloned urea transporter proteins, and the use of these antibodies in integrative animal studies has resulted in several novel findings, including: (1) 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; (2) vasopressin increases UT-A1 phosphorylation in rat inner medullary collecting duct; (3) UT-A protein abundance is upregulated in uremia in both liver and heart; and (4) UT-B is expressed in many nonrenal tissues and endothelial cells. This review will summarize the knowledge gained from using molecular approaches to perform integrative studies into urea transporter protein regulation, both in normal animals and in animal models of human diseases, including studies of uremic rats in which urea transporter protein is upregulated in liver and heart.
Sands
Jeff M
JM
Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA. jsands@emory.edu
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism; D007671:Kidney Concentrating Ability / Q000502:physiology; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000502:physiology; D026901:Membrane Transport Proteins; D014511:Uremia / Q000378:metabolism; D000096982:Urea Transporters
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D000096982:Urea Transporters