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

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

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Homeostasis
  • Humans
  • Hyperkalemia / metabolism
  • Hyperkalemia / physiopathology
  • Kidney / metabolism*
  • Kidney / physiopathology
  • Potassium / metabolism*
  • Urea / metabolism*
  • Water-Electrolyte Balance

Substances

  • Urea
  • Potassium