Molecular cell biology and physiology of solute transport: Edited by Alan YuIntrarenal urea recycling leads to a higher rate of renal excretion of potassium an hypothesis with clinical implicationsKamel, Kamel S.a,b; Halperin, Mitchell L.a,b Author Information aKeenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital bDivision of Nephrology, University of Toronto, Toronto, Ontario, Canada Correspondence to Mitchell L. Halperin, MD, Division of Nephrology, St. Michael's Hospital, Room 5-078, Shuter Street Wing, 30 Bond Street, Toronto, ON M5B 1W8, Canada Tel: +1 416 864 5292; fax: +1 888 3259302; e-mail: [email protected] Current Opinion in Nephrology and Hypertension 20(5):p 547-554, September 2011. | DOI: 10.1097/MNH.0b013e328349b8f9 Buy Metrics Abstract Purpose of review This review aims to illustrate why urea recycling may play an important role in potassium (K+) excretion and to emphasize its potential clinical implications. Recent findings A quantitative analysis of the process of intrarenal urea recycling reveals that the amount of urea delivered to the distal convoluted tubule is about two-fold larger than the quantity of urea excreted in the urine. As the number of osmoles delivered to the late cortical distal nephron (CCD) determines its flow rate when aquaporin 2 water channels have been inserted in the luminal membrane of principal cells, urea recycling may play an important role in regulating the rate of excretion of K+ when the distal delivery of electrolytes is not very high. Summary Urea recycling aids the excretion of K+; this is especially important in patients with disorders or those who are taking drugs that lead to a less lumen-negative voltage in the CCD. As a large quantity of urea is reabsorbed daily in the inner medullary collecting duct, the assumption made in the calculation of the transtubular K concentration gradient that there is no appreciable reabsorption of osmoles downstream CCD is not valid. © 2011 Lippincott Williams & Wilkins, Inc.