Effects of mucosal lanthanum on electrical parameters of isolated frog skin. Mechanism of action.

The effect of mucosal La3+ on electrical parameters of isolated frog skins was studied on isolated frog skins with normally polarized or depolarized apical membrane. La3+ increases R8, the paracellular or shunt resistance and diminishes RNa, the resistance of the active sodium path, in both polarized and depolarized skins. The stimulatory effect of La3+ on short-circuit current (Is.c.) is correlated with this decrease in RNa. The characteristics of the stimulatory effect are: very rapid onset, ionic strength dependency, the possibility of being elicited by many other ions besides La3+. These features allow us to postulate that La3+ might affect the external interfacial potential which in turn affects the resistance of the sodium path.