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

The short-term effect of prolactin on the skin of the adult tree frog Hyla arborea japonica was investigated using current-fluctuation analysis. Basolateral application of ovine prolactin (10 microg ml(-1)) (1) increased the amiloride-blockable short-circuit current (SCC) across the skin 2.6+/-0.4-fold and (2) increased the open-channel density (M) of the epithelial Na(+) channel 6.1+/-1.2-fold but decreased the single-channel current i to 0.4+/-0.1 times the control value (N=9). The increase in SCC induced by prolactin was thus due to an increase in M, not i. Apparently, in amphibians prolactin has not only a counteracting effect on metamorphosis but also a stimulatory effect on the development of adult-type features, such as this amiloride-blockable SCC.