Urinary excretion of aquaporin-2 in humans: A potential marker of collecting duct responsiveness to vasopressin

Sharon Elliot, Paul Goldsmith, Mark Knepper, Mary Haughey, Beatriz Olson

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The vasopressin-sensitive water channel (aquaporin 2; AQP-2) mediates water transport across the apical plasma membrane of the renal collecting ducts and is excreted in human urine. This study presents the hypothesis that measurements of the AQP-2 excretion rate might be used as a marker of collecting-duct responsiveness to vasopressin, and therefore could be useful in the clinical evaluation of various water-balance disorders. This study presents information about the development of an antibody to human AQP-2, and measures the urinary excretion of AQP-2 by quantitative Western analysis. A standard curve of band densities was generated by using known quantities of the modified immunizing peptide to derive the amount of AQP-2 contained in aliquots of urine. AQP-2 urinary excretion changed with short-term alterations in hydration status produced either by water loading (76% decrease, P < 0.01) or by 3% sodium chloride (760% increase, P < 0.01). Steady-state 24-h urinary excretion of AQP-2 was 43 ± 10 nmol/24 h (or 28.5 ± 6.9 pmol/mg creatinine), and 20 ± 6 nmol/24 h (or 18.3 ± 7.9 pmol/mg creatinine) in men and women, respectively. Therefore, urinary AQP-2 excretion can be quantified by using Western analysis, and may serve as a marker of collecting-duct responsiveness to vasopressin in different physiologic settings.

Original languageEnglish (US)
Pages (from-to)403-409
Number of pages7
JournalJournal of the American Society of Nephrology
Issue number3
StatePublished - Mar 1 1996
Externally publishedYes



  • Collecting duct
  • Osmotic
  • Urinary excretion
  • Water channel

ASJC Scopus subject areas

  • Nephrology

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