Figure 3. Effects of extracellular ATP and pH on S_in.

A, current-voltage relations of S_in elicited by 50 μM ATP (•), 1 mM ATP (○), or 1 mM ACh (▵). Data are from 5–13 follicles (2-3 frogs) in each condition held at -60 mV. B, superimposed current traces representative of the S_in elicited by the agonists at membrane potentials from +40 to -120 mV. Horizontal lines indicate zero current. C, superimposed current traces obtained at the peak of S_in elicited by 50 μM ACh at the membrane potentials stepped to +80 and +60 mV from a holding potential of -60 mV. At each potential the set of current traces corresponds with S_in generated in extracellular medium buffered to pH 8, 7, or 6. The inactivation kinetics at +80 mV were fitted to simple exponentials and the mean of the time constants (τ) in each value of extracellular pH were plotted in the bar graph. The open bars are the mean τ inactivation for the I_Cl,swell generated by HR₈₀ (3 follicles, 2 frogs), while the filled bars are those for the S_in elicited by 50 μM ACh in HR₉₀ (7 follicles, 2 frogs) in follicles from the same frogs.