Figure 3. Effect of proton transport inhibitors on I_eq and net HCO₃⁻ secretion across Calu-3 ‘Alter’ shRNA control cells.

A, ouabain (100 μmol l⁻¹) had no effect when added to the apical side to inhibit putative H⁺/K⁺-ATPase (n= 3), B and C, pretreatment with the V-ATPase inhibitor bafilomycin (50 nmol l⁻¹), increased basal- and forskolin-stimulated HCO₃⁻ secretion (n= 3). D, apical addition of ZnCl₂ (nominally 1 mmol l⁻¹) to block putative H⁺ channels increased I_eq and HCO₃⁻ secretion (n= 3). •, I_eq; º, HCO₃⁻ secretion. ***P < 0.001.