Fig. 2. Typical examples of effect of CDPC in the presence or absence of prolactin (PRL). CDPC (50-800 µmol l^-1) was applied to the apical side of tree frog skin at the indicated times and the current-noise power-density spectra were measured at each concentration of CDPC (control condition). CDPC was then washed from the apical side (`wash'). Next, PRL (10 µg ml^-1) was applied to the basolateral side of the skin and CDPC (50-800 µmol l^-1) was again applied to the apical side. The current-noise power-density spectra were measured at each concentration of CDPC (PRL condition). At the end of the experiment, amiloride (Am; 10^-4 mol l^-1) was applied to the apical side to allow measurement of the amiloride-insensitive SCC.