Diphenylamine-2-carboxylate stimulates sodium ion transport in frog skin epithelium

1. Diphenylamine-2-carboxylate (DPC), added to the mucosal side of the frog skin, increased reversibly the short-circuit current (I0), even in SO2-(4) Ringer. Amiloride blocked this effect. 2. The maximal stimulation was 140% of the control value and the EC50 was 0.26 mM DPC. 3. The stimulatory effect of DPC was additive to that of oxytocin. 4. The dose-response curves for amiloride determined in the absence and in the presence of 1 mM DPC showed an IC50 of 1.0 microM and 0.8 microM amiloride, respectively. 5. Thus DPC, a blocker of Cl- channels in various Cl-transporting epithelia, exerts a stimulatory effect on the amiloride-sensitive Na+ transport in frog skin.