Prolactin action on short circuit current in the developing tadpole skin: A comparison with ADH

Abstract

The effect of prolactin (PRL) on active sodium transport was investigated in isolated ventral skins of bullfrog tadpoles, stages XXII–XXV. Short circuit current (SCC) was measured as an indicator of active sodium transport. A dose-response study of stage XXV skins showed no response to PRL at a concentration of 0.5 μg/ml; however, SCC increased with PRL concentrations of 5.0 and 10.0 μg/ml. Addition of PRL, 10.0 μg/ml, to the serosal solution produced a 30–40% increase in SCC and this effect plateaued within 60–80 min using stages XXIII and XXIV skins, but the peak response was observed in only 20 min with stage XXV skins. Stage XXII skins were relatively unresponsive to this concentration of PRL. In order to demonstrate that the PRL response was not due to antidiuretic hormone (ADH) contamination, these studies were repeated using ADH. Using a concentration of ADH threefold that reported for possible ADH contamination in 5 μg/ml PRL, i.e., 2 mU ADH/mg PRL, no changes in SCC were observed. Also, no differences were observed in the ADH response (4.5 mU/ml) at the different stages. All stages demonstrated a peak SCC response (90–140% increase) between 20 and 30 min. These results demonstrate that PRL may have a direct effect on ventral skin active sodium transport, as reflected by alterations in SCC.