Effect of intracellular acidification on colonic NaCl absorption

P. C. Dagher, R. W. Egnor, A. N. Charney

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29 Scopus citations

Abstract

CO2 stimulates Na+ and Cl- absorption in rat distal colon. This is most likely due to intracellular generation of H+ and HCO3 and stimulation of apical NA+-H+ and Cl--HCO3 exchangers. We examined whether intracellular acidification by means other than CO2 would also stimulate Na+ absorption. Stripped segments of distal colon from male Sprague-Dawley rats were studied under short-circuit conditions in Ussing chambers. Identically prepared tissues were used for intracellular pH (pH(i)) measurements with the pH- sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. When the Ringer PCO2 was increased from 20 to 34 mmHg, pH(i) decreased from 7.50 ± 0.04 to 7.35 ± 0.04 and net Na absorption increased from 2.4 ± 0.7 to 3.7 ± 0.7 μeq · cm-2 · h-1. A similar degree of intracellular acidification was obtained with 2.6 μM nigericin, but no stimulation of Na+ absorption was seen. When Ringer-HCO3/- concentration was reduced from 39 to 11 mM at constant PCO2 = 35 mmHg, pH(i) decreased from 7.55 ± 0.02 to 7.11 ± 0.02 with no effect on net Na+ absorption. A similar reduction in pH(i) in a CO2-HCO3-free, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered Ringer also did not stimulate Na+ absorption. Methazolamide had no effect on steady state pH(i) at any given PCO2 but caused marked reductions in net Na+ absorption (9.6 ± 2.4 to 5.2 ± 1.2 μeq · cm-2 · h-1 at PCO2 = 70 mmHg). We conclude that Na+ absorption in rat distal colon is not stimulated by intracellular acidification per se but rather has an absolute requirement for CO2 and carbonic anhydrase activity.

Original languageEnglish (US)
Pages (from-to)G569-G575
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume264
Issue number3 27-3
StatePublished - Jan 1 1993

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Keywords

  • carbon dioxide
  • carbonic anhydrase
  • intracellular pH
  • methazolamide
  • nigericin

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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