Figure 11. The chloride dependence of the surface pH (pH_s) in the distal colon of guinea-pig.

A, in the presence of bicarbonate (KH) chloride was removed (Cl-free) from the mucosal (m) or the serosal (s) side. B, in bicarbonate-free 21 mmol l⁻¹ Hepes buffer solution (HCO₃-free), chloride was removed from the mucosal solution in the absence or in the presence of 21 mmol l⁻¹ butyrate (Bu) on both sides of the epithelium. C, addition of 0.2 mmol l⁻¹ H₂-DIDS to the mucosal KH in the presence or absence of chloride. All solutions had been titrated to pH 7.4.