Figure 3. Effects of forskolin on Cl⁻ flux across the luminal membrane in the presence of HCO₃⁻/CO₂.

Initially the bath and lumen of the duct segments were perfused with the standard HCO₃⁻-buffered solution. A, forskolin (1 μm) was applied to the bath and then the luminal perfusate was switched to the low Cl⁻-high HCO₃⁻ solution in the continued presence of forskolin. One of seven experiments. B, the luminal membrane was pretreated with H₂DIDS (200 μm) and forskolin (1 μm) was applied to the bath. One of four experiments. C, the luminal perfusate was switched to the low Cl⁻-high HCO₃⁻ solution in the absence and presence of forskolin (1 μm). One of five experiments.