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Prolactin increases open-channel density of epithelial Na⁺ channel in adult frog skin

Makoto Takada^* and Miyoko Kasai

Department of Physiology, Saitama Medical School, Moroyama, Iruma-gun, Saitama, 3500495 Japan

View larger version (16K): [in a new window]   Fig. 4. Blocker-dependent changes in 2fc (see Equation 2) and short-circuit current (i). The blocking K01 and and unblocking K10 coefficients for CDPC are determined from the slope and intercept on the ordinate of corner-frequency plots (A). The single-channel current was calculated by extrapolation of the CDPC concentration versus i curve to the ordinate (B). Values are means ± S.E.M.; N=9.

View larger version (15K): [in a new window]   Fig. 1. A typical example of the effect of prolactin (PRL) on short-circuit current (SCC) I tree frog skin (inset shows data for the initial phase of response). Values are means ± S.E.M.; N = number of experiments. PRL (10 µg ml-1) was applied to the basolateral side of the skin and amiloride (Am; 10-4 mol l-1) to the apical side, at the times shown.

View larger version (12K): [in a new window]   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.

View larger version (28K): [in a new window]   Fig. 3. Summary of effect of prolactin (PRL; 10 µg ml-1) on short-circuit current (SCC; i), Na+ channel density (M), K01 and K10 (blocking and unblocking rate coefficients, respectively) and Km of adult skin of tree frog. Values are means ± S.E.M.; N=9. Asterisks show a significant difference (P<0.05) from control values (before PRL).