Urea transporters (UTs) are expressed in kidney tubules and microvessels, and in extrarenal tissues. An intrarenal urea recycling process through urea transporters (UTs) is believed to be important in the urinary concentrating mechanism and thus water conservation. We recently generated and analyzed UT-B deficient mice, the first animal model of UT deficiency. Our data provided evidence that UT-B-dependent countercurrent exchange of urea in the renal medulla contributes to approximately one-third of the kidney's total capacity to concentrate urine, but contributes even more greatly to the ability of the kidney to concentrate urea itself. The purpose of this proposal is to generate transgenic mice that lack other UTs, and to characterize their role in the kidney.
In Aim 1, we propose to generate: UT-A2 knockout, UT-A2/UT-B double knockout and UT-A1/A3/A4 triple knockout mice by various targeting strategies. The generation of these mice is technically feasible and appropriate to address specific questions in renal physiology: UT-A2 and UT-A2/UT-B knockout mice to study urea recycling and urea reintroduction into descending limb of Henle's loops and vasa recta, and UT-A1/A3/A4 triple knockout mice to study urea delivery to the tip of the papilla.
In Aim 2, renal function in wild type and knockout mice will be studied systematically by classical urine/plasma collection methods using metabolic cages. The urinary concentrating mechanism will be analyzed under normal and stressed conditions (water deprivation, water-loading, high/low protein diet). These experiments will permit the definitive testing of hypotheses regarding the role of intrarenal urea recycling in the urine concentrating mechanism (roles of urea efflux from collecting duct and urea influx into vasa recta and descending limb of Henle's loops), and provide the first quantitative data on the role of specific UTs. Together the data should provide novel and definitive data regarding the role of specific UTs in mammalian renal physiology and new insights into pathological conditions such as chronic renal failure and hypertension. Also, the new information may provide a rational basis for discovery of UT inhibitors as unique diuretic agents.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21DK066194-02
Application #
6847156
Study Section
General Medicine B Study Section (GMB)
Program Officer
Ketchum, Christian J
Project Start
2004-07-01
Project End
2007-06-30
Budget Start
2005-07-01
Budget End
2007-06-30
Support Year
2
Fiscal Year
2005
Total Cost
$151,500
Indirect Cost
Name
University of California San Francisco
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Yang, Baoxue; Zhao, Dan; Verkman, A S (2009) Hsp90 inhibitor partially corrects nephrogenic diabetes insipidus in a conditional knock-in mouse model of aquaporin-2 mutation. FASEB J 23:503-12
Zhao, Dan; Sonawane, N D; Levin, Marc H et al. (2007) Comparative transport efficiencies of urea analogues through urea transporter UT-B. Biochim Biophys Acta 1768:1815-21
Guo, Lirong; Zhao, Dan; Song, Yuanlin et al. (2007) Reduced urea flux across the blood-testis barrier and early maturation in the male reproductive system in UT-B-null mice. Am J Physiol Cell Physiol 293:C305-12
Yang, Baoxue; Kim, Jung Kyung; Verkman, A S (2006) Comparative efficacy of HgCl2 with candidate aquaporin-1 inhibitors DMSO, gold, TEA+ and acetazolamide. FEBS Lett 580:6679-84
Zhao, Dan; Bankir, Lise; Qian, Liman et al. (2006) Urea and urine concentrating ability in mice lacking AQP1 and AQP3. Am J Physiol Renal Physiol 291:F429-38
Yang, Baoxue; Zhao, Dan; Verkman, A S (2006) Evidence against functionally significant aquaporin expression in mitochondria. J Biol Chem 281:16202-6
Yang, Baoxue; Zhao, Dan; Solenov, Eugene et al. (2006) Evidence from knockout mice against physiologically significant aquaporin 8-facilitated ammonia transport. Am J Physiol Cell Physiol 291:C417-23
Yang, Baoxue; Zhao, Dan; Qian, Liman et al. (2006) Mouse model of inducible nephrogenic diabetes insipidus produced by floxed aquaporin-2 gene deletion. Am J Physiol Renal Physiol 291:F465-72
Yang, Baoxue; Song, Yuanlin; Zhao, Dan et al. (2005) Phenotype analysis of aquaporin-8 null mice. Am J Physiol Cell Physiol 288:C1161-70
Meng, Yan; Zhou, Xueyan; Li, Yang et al. (2005) A novel mutation at the JK locus causing Jk null phenotype in a Chinese family. Sci China C Life Sci 48:636-40

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