Vasopressin, theophylline, PGE2, and indomethacin on active Na transport in frog skin: studies with microelectrodes.

Active transepithelial Na transport in frog skin is influenced by vasopressin, theophylline, indomethacin, and PGE2. During stimulation or inhibition of the short-circuit current, the transapical membrane voltage of short-circuited skins was recorded using an intracellular microelectrode. The microelectrode also permitted determination of the fractional resistance of the apical barrier of the cells (fRo) and the E'1 (transepithelial voltage at which the apical membrane voltage is zero). Analysis of the data according to an electrical model proposed previously indicated that changes of ISC were mediated primarily via changes of the slope resistance Rfo (Vo negative) of the apical barrier of the cells with little or no effect on the Thévenin emf or resistance of the basolateral membranes. These data are in accordance with previous observations that ADH had no effect on the ENa and are discussed in relation to the origin of the ENa at the basolateral membranes of the epithelial cells.