Effects of Anions on Frog Ventricle

Abstract

The effects of replacement of external chloride by other anions on the electrical and mechanical properties of frog ventricular muscle have been studied.The effects of methylsulfate were similar to those expected for replacement of a permeant anion with an impermeant anion. Increased twitch tension was largely dependent on action potential prolongation. Other anions of the sulfate–sulfonate series produced similar changes, but minor differences in their actions indicated that their effects could not be explained entirely by the elimination of chloride current.Acetate and its analogues produced dramatic changes in both the electrical and mechanical properties of frog heart. All caused a marked hyperpolarization of the resting membrane potential, accompanied by characteristic changes in the shape and duration of the repolarization phase of the action potential. Enhanced contractile performance was characterized by an increased rate of tension development and a slow onset of relaxation. These effects were equally prominent upon transfer to acetate Ringer's solution after previous equilibration to a medium containing methylsulfate in place of chloride. Although similar qualitatively, the members of this series of anions also displayed marked quantitative differences in the intensity and time course of their effects.