The interaction of potassium with the activation of anomalous rectification in frog muscle membrane.

Abstract

Inward rectification of frog muscle membrane was analyzed with the vaseline gap method. Hyperpolarization under voltage clamp produced inward K currents which had a component that activated with a time constant, .kappa.K. The activation time constant .kappa.K of the inward K currents was voltage-dependent. For a given external K concentration, the time constant was maximal for potentials near the K equilibrium potential, EK. The K chord conductance gK had a sigmoidal voltage dependency, increasing initially e-fold per 11.6 mV of hyperpolarization. When the internal K concentration was fixed, raising external K induced a shift of the .kappa.K-V and the gK-V relations in the positive direction along the voltage axis. The shift was comparable to the change in EK. No shift of the .kappa.K-V and the gK-V relations was observed when the internal K was reduced from 150 to 50 mM. Changes of internal Na concentration between 5-100 mM did not significantly affect the magnitude of inward rectification.