Responses to salinity and the effect of prolactin on whole animal transepithelial potential in the gobiid teleost, Gillichthys mirabilis.

Whole-animal transepithelial potential (TEP) of the goby, Gillichthys mirabilis, was measured. TEP was the same whether the electrode was implanted in the dorsal muscle or in the peritoneal cavity. TEP response to different salinities was linear from 0 to 100% seawater, and stable from 100 to 200% seawater. TEP decreased significantly in 225 and 250% seawater, and the fish became dehydrated. Plasma Na and Cl concentrations showed a linear relationship with increase in salinity from 0 to 200% seawater. In hypophysectomized Gillichthys, TEP was significantly lower than in sham-operated fish, but hypophysectomized fish with a rostral pars distalis autotransplant showed TEP similar to that of intact fish. Plasma Na and Cl in hypophysectomized fish were lower than in intact and RPD-autotransplanted fish, suggesting that prolactin is involved in maintaining normal whole-animal TEP.