Ouabain reduces net acid secretion and increases pHi by inhibiting NH4+ uptake on rat tIMCD Na(+)-K(+)-ATPase

The American Journal of Physiology
S M Wall

Abstract

In the rat terminal inner medullary collecting duct (tIMCD), Na+ pump inhibition reduces transepithelial net acid secretion (JtAMM) [JH = total CO2 absorption (JtCO2)+ total ammonia secretion] and increases resting intracellular pH (pHi). The increase in pHi and reduction in JH that follow ouabain addition do not occur in the absence of NH4+ nor when NH4+ is substituted with another weak base. The purpose of this study was to explore the mechanism of the NH4(+)-dependent reduction in JtCO2 and increase in pHi that follow ouabain addition. We hypothesized that NH4+ enters the tIMCD cell through the Na(+)-K(+)-ATPase with proton release in the cytosol. To test this hypothesis, tIMCDs were dissected from deoxycorticosterone-treated rats and perfused in vitro with symmetrical physiological saline solutions containing 6 mM NH4Cl. Since K+ and NH4+ compete for a common binding site on the Na+ pump, increasing extracellular K+ should limit NH4+ (and hence net H+) uptake by the Na+ pump. Upon increasing extracellular K+ concentration from 3 to 12 mM, the NH4(+)-dependent, ouabain-induced increase in pHi and reduction in JtCO2 were attenuated. In the presence but not in the absence of NH4+, reducing Na+ pump activity by limiting Na+ ent...Continue Reading

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Citations

Mar 27, 2009·American Journal of Physiology. Renal Physiology·Hyun-Wook LeeI David Weiner
May 29, 2015·American Journal of Physiology. Renal Physiology·Masayoshi NanamiSusan M Wall
Sep 28, 2006·Annual Review of Physiology·I David Weiner, L Lee Hamm
May 20, 2004·American Journal of Physiology. Renal Physiology·Mary E HandlogtenI David Weiner
Jan 9, 2009·American Journal of Physiology. Renal Physiology·Hye-Young KimI David Weiner
Aug 20, 2010·American Journal of Physiology. Renal Physiology·Jesse M BishopI David Weiner
Sep 24, 2004·Physiological Reviews·Carsten A WagnerJohn P Geibel
Mar 31, 2005·American Journal of Physiology. Renal Physiology·Mary E HandlogtenI David Weiner
Dec 12, 2012·American Journal of Physiology. Renal Physiology·Jesse M BishopI David Weiner
Nov 5, 2010·American Journal of Physiology. Renal Physiology·I David Weiner, Jill W Verlander
Dec 12, 2001·American Journal of Physiology. Renal Physiology·Susan M WallKathryn A Hassell

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