Modulation of chloride secretion in the rat ileum by intracellular bicarbonate

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Abstract

Increasing intracellular bicarbonate concentration ([HCO3-](i)) inhibits calcium-mediated Cl- secretion in rat distal colon and T84 cells. We investigated the effect of [HCO3-](i) on Cl- secretion in rat ileum. Segments of intact ileum from Sprague-Dawley rats were studied in Ussing chambers and villus and crypt intracellular pH and [HCO3-](i) were determined using BCECF. A range of crypt and villus [HCO3-](i) from 0 to 31 mM was obtained by varying Ringer's composition. Basal serosal-to-mucosal Cl- flux (J(sm)(Cl)) averaged 8.5 ± 0.2 μeq·h-1·cm-2 and was unaffected by changing [HCO3-](i) or serosal bumetanide. Carbachol increased J(sm)(Cl) by 39 ± 0.5 μeq·h-1·cm-2 at [HCO3-] (i) = 0 mM but only by 1.0 ± 0.3 μeq·h-1·cm-2 at high crypt and villus [HCO3-](i). Dibutytyl-cAMP increased J(sm)(Cl) by 2.5 ± 0.2 μeq. h-1·cm-2 at all [HCO3-](i). Carbachol and db-cAMP showed mutual antagonism at low [HCO3-](i) and near-additivity at high [HCO3-](i). We conclude that like rat colon and T84 cells, calcium-mediated but not cAMP-mediated Cl- secretion in the ileum is inhibited by increasing [HCO3-](i). Mutual antagonism between carbachol and db-cAMP at low [HCO3-](i) was present in ileum and distal colon but not in T84 cells.

Original languageEnglish (US)
Pages (from-to)89-97
Number of pages9
JournalComparative Biochemistry and Physiology - A Physiology
Volume117
Issue number1
DOIs
StatePublished - May 1 1997

Keywords

  • bicarbonate
  • cAMP
  • carbachol
  • colon
  • intracellular hydrogen ion concentration

ASJC Scopus subject areas

  • Physiology

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