Glucocorticoids stimulate Na+/H+ antiporter in OKP cells

Michel Baum, Adriana Cano, Robert J. Alpern

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Abstract

Previous studies have demonstrated that systemic administration of glucocorticoids stimulates proximal tubule acidification in part by increasing Na+/H+ antiporter activity; however, these studies could not exclude the possibility that changes in Na+/H+ antiporter activity were secondary to glucocorticoid-induced hemodynamic changes. The present study examined the effect of dexamethasone on Na+/H+ antiporter activity in quiescent OKP cells. Na+/H+ antiporter activity was assayed as the initial rate of Na+-dependent pH recovery from an acid load. Intracellular pH was measured using the pH-sensitive dye 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Dexamethasone produced a dose- and time-dependent stimulation of Na+/H+ antiporter activity in OKP cells. Dexamethasone produced a 24% stimulation in Na+/H+ antiporter activity at 10-9 M and an ∼40% stimulation of Na+/H+ antiporter activity at both 10-8 and 10-6 M. The effect of 10-6 M dexamethasone was seen within 4 h of incubation and was due to an increase in maximal velocity (Vmax, 3.03 vs. 1.79 pH units/min) with no change in the affinity constant for sodium (KNa, 47.2 vs. 42.0 mM). The stimulatory effect of dexamethasone on Na+/H+ antiporter activity was blocked by cycloheximide and was not observed with 10-8 M aldosterone. These data demonstrate a direct effect of glucocorticoids to stimulate Na+/H+ antiporter activity in OKP cells.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume264
Issue number6 33-6
StatePublished - Jun 1993

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Sodium-Hydrogen Antiporter
Glucocorticoids
Dexamethasone
Cycloheximide
Aldosterone
Hemodynamics
Sodium
Acids

Keywords

  • Acidification
  • Dexamethasone
  • Sodium/hydrogen exchanger

ASJC Scopus subject areas

  • Physiology

Cite this

Glucocorticoids stimulate Na+/H+ antiporter in OKP cells. / Baum, Michel; Cano, Adriana; Alpern, Robert J.

In: American Journal of Physiology - Renal Fluid and Electrolyte Physiology, Vol. 264, No. 6 33-6, 06.1993.

Research output: Contribution to journalArticle

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