Modulation of secretagogue-induced chloride secretion by intracellular bicarbonate

P. C. Dagher, T. Z. Morton, C. S. Joo, A. Taglietta-Kohlbrecher, R. W. Egnor, A. N. Charney

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11 Scopus citations


We have previously demonstrated inhibition of basal Cl- secretion by intracellular bicarbonate concentration ([HCO3/-](i)) in rat distal colon. We now examined whether secretagogue-induced Cl- secretion is inhibited by [HCO3/-](i) as well. Stripped segments of distal colon from male Sprague- Dawley rats and the colon tumor cell line T84 were studied. Flux measurements were performed in the Ussing chamber under short-circuit conditions. [HCO3/-](i) was calculated from intracellular pH (pH(i)) values that were estimated with the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)- carboxyfluorescein. Dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) and carbachol were used as secretagogues. In both distal colon and T84 cells, [HCO3/-](i) did not affect cAMP-induced Cl- secretion. However, carbachol- induced secretion was inhibited by [HCO3/-](i); in rat colon, Cl- secretion decreased from 2.3 to 1.5 μeq · cm-2 · h-1 when [HCO3/- ](i) was increased from 15.0 to 28.4 mM (P < 0.05). In T84 cells, the change in short-circuit current decreased from 8.1 to 1.1 μA/cm2 over a range of [HCO3/-](i) from 0 to 15.6 mM (P < 0.001). We conclude that [HCO3/-](i) is an important modulator of carbachol-stimulated Cl- secretion in both rat distal colon and the T84 cell line. cAMP-mediated secretion is not affected by [HCO3/-](i).

Original languageEnglish (US)
Pages (from-to)G929-G934
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number5 29-5
StatePublished - Jan 1 1994
Externally publishedYes


  • T84 cells
  • adenosine 3',5'-cyclic monophosphate
  • carbachol
  • rat distal colon

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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