Isoproterenol-induced current changes in glands of frog skin

Abstract

In this study we report on isoproterenol-induced changes in short-circuit current (SCC) that are located in the glands of the frog skin. Following complete inhibition of the SCC with amiloride (10(-4) M), the addition of isoproterenol (9.0 X 10(-7) M) to the serosal side of the skin elicits a significant increase in SCC from 0.6 +/- 0.1 to 3.9 +/- 0.5 microA/cm2 (p less than 0.001). The conductance is doubled, and both effects are blocked completely with the beta-blocking agent propranolol. In the split-skin preparation, in which no glands are present, there is no current response to isoproterenol following amiloride. This indicates that the amiloride-insensitive isoproterenol-stimulated SCC resides in the glands. In the intact skin, removal of sodium (choline replacement) from the serosal (but not the mucosal) medium abolishes this current change. The postisoproterenol current change in amiloride-inhibited skins is also dependent on the presence of chloride in the serosal bath. Preincubation of the amiloride-inhibited skin with ouabain (10(-4) M) for 10 min prior to the addition of isoproterenol reduces the isoproterenol response by 50%. These results indicate that there is a sodium- and chloride-dependent ouabain-sensitive secretory mechanism in the skin glands of the frog that is responsible for the development of the isoproterenol-stimulated SCC observed in the presence of amiloride.