Paradoxical Influence of Calcium Ions on the Permeability of the Cell Membranes of the Isolated Rat Heart

IN the course of an investigation of the specificity of acetoacetate which causes electromechanical dissociation 1 we found that pyruvate also inhibited contractility of the rat heart and dog heart, leaving electrical activity intact 2 . Later we found that perfusion of the heart with sodium citrate caused essentially the same phenomenon. Although the inhibition of cardiac contraction by potassium citrate has already been demonstrated by Melrose et al. 3 , it is essential to use sodium citrate in order to demonstrate electromechanical dissociation, as high potassium-levels per se inhibit electrical activity.