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Curr Opin Nephrol Hypertens. 2011 Sep;20(5):547-54. doi: 10.1097/MNH.0b013e328349b8f9.

Intrarenal urea recycling leads to a higher rate of renal excretion of potassium: an hypothesis with clinical implications.

Author information

1
Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Division of Nephrology, University of Toronto, Toronto, Ontario, Canada.

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.

PMID:
21788894
DOI:
10.1097/MNH.0b013e328349b8f9
[Indexed for MEDLINE]

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