Phasic efflux of potassium from frog ventricle

¹ Department of Physiology, University of Minnesota School of Medicine, Minneapolis, Minnesota

A phasic effiux of K⁴² during the cardiac cycle, first described by Wilde in the turtle heart, has been observed in perfused strips of frog ventricle. This was shown to represent an actual increase in the outward movement of K, occurring during the action potential, and of approximately the same duration as the electrical transient. Perfusion with K-free Ringer's prolonged both events, and, within the limits of resolution of the method, appeared to do so to about the same extent. The level of K in the perfusion medium was found to have a pronounced effect on the K efflux, a result which may be interpreted in terms of an effect of extracellular [K⁺] on the permeability of the cell membrane to K. The finding that the increase in K efflux observed during the action potential is much smaller than that predicted from the increase in the voltage gradient (assuming the voltage gradient to be the only variable) is consistent with a diminished K conductance during the action potential.