HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 286/1/F144    most recent 00205.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (16) Citing Articles via Google Scholar Google Scholar Articles by Bankir, L. Articles by Yang, B. Search for Related Content PubMed PubMed Citation Articles by Bankir, L. Articles by Yang, B.

Lack of UT-B in vasa recta and red blood cells prevents urea-induced improvement of urinary concentrating ability

¹Departments of Medicine and Physiology, Cardiovascular Research Institute, University of California, San Francisco, California 94143-0521; and ²Institut National de la Santé et de la Recherche Médicale Unit 367, Institut du Fer a Moulin, 75005 Paris, France

Submitted 30 May 2003 ; accepted in final form 29 August 2003

Recycling of urea within the renal medulla is known to play an important role in the capacity of the kidney to concentrate urine. This recycling occurs simultaneously through a tubular and a vascular route (i.e., through the loops of Henle and vasa recta, respectively). In the present study, transgenic mice with a selective deficiency in UT-B (the urea transporter protein expressed in descending vasa recta and red blood cells), were used to evaluate the specific contribution of vascular urea recycling to overall urine-concentrating ability (UCA). The renal handling of urea was studied in normal conditions and after acute or chronic alterations in urea excretion (acute urea loading or variations in protein intake, respectively). In normal conditions, UT-B null mice exhibited a 44% elevation in plasma urea (P_urea), a normal creatinine clearance, but a 25% decrease in urea clearance, with no change in that of sodium and potassium. Acute urea loading induced a progressive increase in urinary urea concentration (U_urea) in wild-type mice and a subsequent improvement in their UCA in contrast to UT-B null mice, in which urinary osmolality and U_urea did not rise, due to the failure to accumulate urea in the medulla. With increasing protein intake (from 10 to 40% protein in diet, leading to a 5-fold increase in urea excretion), P_urea was further increased in null mice while little change was observed in wild-type mice, and null mice were not able to increase U_urea as did wild-type mice. In conclusion, this study in UT-B-deficient mice reveals that countercurrent exchange of urea in renal medullary vessels and red blood cells accounts for a major part of the kidney's concentrating ability and for the adaptation of renal urea handling during a high-protein intake.

urea transport; protein intake; urinary concentrating ability; creatinine clearance; urea clearance

This article has been cited by other articles:

				G. S. Stewart, J. H. O'Brien, and C. P. Smith Ubiquitination regulates the plasma membrane expression of renal UT-A urea transporters Am J Physiol Cell Physiol, July 1, 2008; 295(1): C121 - C129. [Abstract] [Full Text] [PDF]

				R. A. Fenton and M. A. Knepper Mouse Models and the Urinary Concentrating Mechanism in the New Millennium Physiol Rev, October 1, 2007; 87(4): 1083 - 1112. [Abstract] [Full Text] [PDF]

				G. S. Stewart, S. L. King, E. A. Potter, and C. P. Smith Acute regulation of mUT-A3 urea transporter expressed in a MDCK cell line Am J Physiol Renal Physiol, April 1, 2007; 292(4): F1157 - F1163. [Abstract] [Full Text] [PDF]

				R. A. Fenton and M. A. Knepper Urea and Renal Function in the 21st Century: Insights from Knockout Mice J. Am. Soc. Nephrol., March 1, 2007; 18(3): 679 - 688. [Abstract] [Full Text] [PDF]

				D. Zhao, L. Bankir, L. Qian, D. Yang, and B. Yang Urea and urine concentrating ability in mice lacking AQP1 and AQP3 Am J Physiol Renal Physiol, August 1, 2006; 291(2): F429 - F438. [Abstract] [Full Text] [PDF]

				S. Uchida, E. Sohara, T. Rai, M. Ikawa, M. Okabe, and S. Sasaki Impaired Urea Accumulation in the Inner Medulla of Mice Lacking the Urea Transporter UT-A2 Mol. Cell. Biol., August 15, 2005; 25(16): 7357 - 7363. [Abstract] [Full Text] [PDF]

				G. S. Stewart, C. Graham, S. Cattell, T. P. L. Smith, N. L. Simmons, and C. P. Smith UT-B is expressed in bovine rumen: potential role in ruminal urea transport Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2005; 289(2): R605 - R612. [Abstract] [Full Text] [PDF]

				B. Yang and L. Bankir Urea and urine concentrating ability: new insights from studies in mice Am J Physiol Renal Physiol, May 1, 2005; 288(5): F881 - F896. [Abstract] [Full Text] [PDF]

				N. Lucien, P. Bruneval, F. Lasbennes, M.-F. Belair, C. Mandet, J.-P. Cartron, P. Bailly, and M.-M. Trinh-Trang-Tan UT-B1 urea transporter is expressed along the urinary and gastrointestinal tracts of the mouse Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2005; 288(4): R1046 - R1056. [Abstract] [Full Text] [PDF]

				J. D. Klein, J. M. Sands, L. Qian, X. Wang, and B. Yang Upregulation of Urea Transporter UT-A2 and Water Channels AQP2 and AQP3 in Mice Lacking Urea Transporter UT-B J. Am. Soc. Nephrol., May 1, 2004; 15(5): 1161 - 1167. [Abstract] [Full Text] [PDF]