Figure 1. Osmolarity-dependent membrane currents elicited in Xenopus follicles.

A, I_Cl,swell elicited by HR₈₀ in a follicle superfused originally in NR, and F_in and S_in elicited by ACh and ATP in follicles bathed in HR₉₀. All different epithelium-removed follicles were held at -60 mV. In this and subsequent records test solutions and drugs were applied during times indicated by bars at top, and steps to -40 mV were applied periodically to monitor membrane conductance. B, current-voltage relationships for I_Cl,swell (•), and S_in elicited in HR₉₀ by 50 μM ACh (○) and 50 μM ATP (▵); steady-state currents at different potentials were measured by application of a voltage step series in control conditions and at the peak of the currents. Superimposed records are examples of currents during the voltage steps to +40 mV during the indicated conditions. Data (here and throughout are quoted as means ±s.e.m.) from follicles of 7–14 frogs.