Effect of intracellular acidification on colonic NaCl absorption

Pierre Dagher, R. W. Egnor, A. N. Charney

Research output: Contribution to journalArticle

29 Citations (Scopus)

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)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume264
Issue number3 27-3
StatePublished - 1993
Externally publishedYes

Fingerprint

Colon
Methazolamide
Chloride-Bicarbonate Antiporters
Nigericin
HEPES
Carbonic Anhydrases
Sprague Dawley Rats
2-(2-(2-chloro-3-(2-(3,3-dimethyl-5-sulfo-1-(4-sulfo-butyl)-3H-indol-2-yl)-vinyl)-cyclohex-2-enylidene)-ethylidene)-3,3-dimethyl-1-(4-sulfo-butyl)-2,3-dihydro-1H-indole-5-carboxylic acid
6-carboxyfluorescein

Keywords

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

ASJC Scopus subject areas

  • Physiology
  • Gastroenterology

Cite this

Effect of intracellular acidification on colonic NaCl absorption. / Dagher, Pierre; Egnor, R. W.; Charney, A. N.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 264, No. 3 27-3, 1993.

Research output: Contribution to journalArticle

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AB - 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.

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