Vasopressin-independent renal urinary concentration: Increased rBSC1 and enhanced countercurrent multiplication

Mari Michimata, Kazuhiko Mizukami, Michiko Suzuki, Itsuro Kazama, Yohsuke Nakamura, Katsuya Suzuki, Teruyuki Yanagisawa, Yutaka Imai, Sei Sasaki, Mitsunobu Matsubara

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Background. A close association between the expression of the sodium transporter, rat bumetanide sensitive cotransporter (rBSC), in thick ascending limb of Henle and urinary concentration has been reported. However, direct evidence for this association and the mechanism of rBSC1 expression are still to be elucidated. Methods. Brattleboro (BB) rats weighing approximately 200 g were dehydrated by water restriction for 4 hours, which induced around a 5% body weight reduction. Although plasma arginine vasopressin (AVP) was undetectable even after the water restriction, BB rats concentrated urine from 182 ± 23 (mean ± SD) at baseline to 404 ± 65 mOsm/kg · H2O. Results. Urinary volume was reduced from 5.8 ± 1.8 to 1.4 ± 0.6 mL/h. This treatment significantly increased sodium and urea accumulation in the renal medulla and reduced urinary sodium excretion. rBSC1 signals for both mRNA and protein were increased in dehydrated rats, although aquaporin type 2 (AQP2) expression was not enhanced in dehydrated BB rats. Subcutaneous infusion of desmopressin acetate (DDAVP) intensified rBSC1 signals of BB rats more than those in dehydrated condition. Conclusion. Dehydration increased rBSC1 expression and enhanced countercurrent multiplication even in AVP deficiency. These results supply strong evidence for the association between rBSC1 expression and urinary concentration, and indicate the presence of an AVP-independent mechanism for urine concentration.

Original languageEnglish
Pages (from-to)933-938
Number of pages6
JournalKidney international
Volume64
Issue number3
DOIs
Publication statusPublished - 2003 Sep 1

Keywords

  • AQP2
  • AVP deficiency
  • Renal medulla
  • Thick ascending limb of Henle

ASJC Scopus subject areas

  • Nephrology

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