Chronic hyperosmolality increases NHE3 activity in OKP cells

Patrice Ambühl, Morimasa Amemiya, Patricia A. Preisig, Orson W. Moe, Robert J. Alpern

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

This study investigated the effect of chronic hypertonicity on the OKP cell Na/H antiporter, encoded by Na/H exchanger 3 (NHE3). Chronic (48 h) increases in extracellular glucose, mannitol, or raffinose concentration caused a significant increase in Na/H antiporter activity, while increases in urea concentration were without effect. This effect was seen with changes in osmolality of only 20 mOsm/liter, a magnitude that is observed clinically in poorly controlled diabetes mellitus. Increases in mannitol concentration acutely inhibited and chronically stimulated Na/H antiporter activity. The increase in Na/H antiporter activity induced by hypertonic incubation was resistant to 10-7 and 5 x 10-6 M but inhibited by 10-4 M ethylisopropyl amiloride, consistent with regulation of NHE3. In addition, hypertonicity increased total cellular and plasma membrane NHE3 protein abundance twofold, with only a small increase in NHE3 mRNA abundance. We conclude that chronic pathophysiologically relevant increases in tonicity lead to increases in NHE3 protein abundance and activity. This may be responsible for increased proximal tubule apical membrane Na/H antiporter activity in poorly controlled diabetes mellitus, which could then contribute to hypertension, glomerular hyperfiltration and diabetic nephropathy.

Original languageEnglish (US)
Pages (from-to)170-177
Number of pages8
JournalJournal of Clinical Investigation
Volume101
Issue number1
DOIs
StatePublished - Jan 1 1998

Keywords

  • Diabetes mellitus
  • Hyperglycemia
  • Hypertension
  • Hypertonicity
  • Na/H antiporter

ASJC Scopus subject areas

  • Medicine(all)

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