Ouabain stimulates Na-K-ATPase through a sodium/hydrogen exchanger-1 (NHE-1)-dependent mechanism in human kidney proximal tubule cells

Kristine A. Holthouser, Amritlal Mandal, Michael L. Merchant, Jeffrey R. Schelling, Nicholas A. Delamere, Ronald R. Valdes, Suresh C. Tyagi, Eleanor D. Lederer, Syed J. Khundmiri

Research output: Contribution to journalArticle

42 Scopus citations

Abstract

Recent investigations demonstrate increased Na/H exchanger-1 (NHE-1) activity and plasma levels of ouabain-like factor in spontaneously hypertensive rats. At nanomolar concentrations, ouabain increases Na-K-ATPase activity, induces cell proliferation, and activates complex signaling cascades. We hypothesize that the activity of NHE-1 and Na-K-ATPase are interdependent. To test whether treatment with picomolar ouabain regulates Na-K-ATPase through an NHE-1-dependent mechanism, we examined the role of NHE-1 in ouabain-mediated stimulation of Na-K-ATPase in kidney proximal tubule cell lines [opossum kidney (OK), HK-2, HKC-5, and HKC-11] and rat kidney basolateral membranes. Ouabain stimulated Na-K-ATPase activity and tyrosine phosphorylation in cells that express NHE-1 (OK, HKC-5, and HKC-11) but not in HK-2 cells that express very low levels of NHE-1. Inhibition of NHE-1 with 5 μM EIPA, a NHE-1-specific inhibitor, prevented ouabain-mediated stimulation of 86Rb uptake and Na-K-ATPase phosphorylation in OK, HKC-5, and HKC-11 cells. Expression of wild-type NHE-1 in HK2 cells restored regulation of Na-K-ATPase by picomolar ouabain. Treatment with picomolar ouabain increased membrane expression of Na-K-ATPase and enhanced NHE-1-Na-K-ATPase α1-subunit association. Treatment with ouabain (1 μg·kg body wt-1·day -1) increased Na-KATPase activity, expression, phosphorylation, and association with NHE-1 increased in rat kidney cortical basolateral membranes. Eight days' treatment with ouabain (1 μg·kg body wt -1·day-1) resulted in increased blood pressure in these rats. These results suggest that the association of NHE-1 with Na-K-ATPase is critical for ouabain-mediated regulation of Na-K-ATPase and that these effects may play a role in cardioglycoside-stimulated hypertension.

Original languageEnglish (US)
Pages (from-to)F77-F90
JournalAmerican Journal of Physiology - Renal Physiology
Volume299
Issue number1
DOIs
StatePublished - Jul 1 2010
Externally publishedYes

Keywords

  • Cardioglycosides
  • Phosphorylation

ASJC Scopus subject areas

  • Physiology
  • Urology

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