Distribution and regulation of apical Cl/anion exchanges in surface and crypt cells of rat distal colon
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Updated: Oct 26, 2026

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique
Published on: May 26, 2021
1Departments of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Abstract:
Na depletion inhibits electroneutral Na-Cl absorption in intact tissues and Na/H exchange in apical membrane vesicles (AMV) of rat distal colon. Two anion (Cl/HCO3 and Cl/OH) exchanges have been identified in AMV from surface cells of rat distal colon. To determine whether Cl/HCO3 and/or Cl/OH exchange is responsible for vectorial Cl movement, this study examined the spatial distribution and the effect of Na depletion on anion-dependent 36Cl uptake by AMV in rat distal colon. These studies demonstrate that HCO3 concentration gradient-driven 36Cl uptake (i.e., Cl/HCO3 exchange) is 1) primarily present in AMV from surface cells and 2) markedly reduced by Na depletion. In contrast, OH concentration gradient-driven 36Cl uptake (i.e., Cl/OH exchange) present in both surface and crypt cells is not affected by Na depletion. In Na-depleted animals HCO3 also stimulates 36Cl via Cl/OH exchange with low affinity. These results suggest that Cl/HCO3 exchange is responsible for vectorial Cl absorption, whereas Cl/OH exchange is involved in cell volume and/or cell pH homeostasis.
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