Contractions of ventricular muscle in absence of certain cations

¹ Baker Medical Research Institute, Melbourne, Australia

The contractile activity of toad, lizard, and tortoise ventricles was investigated during perfusion with isotonic Ca⁺⁺-free solutions containing sucrose, LiCl, and tetraethylammonium chloride instead of NaCl. In the absence of added Ca⁺⁺ contractions were abolished by EDTA and by preliminary perfusion with modified Tyrode solution containing 100 mm Mg⁺⁺. These findings are discussed in accordance with the hypothesis that Ca⁺⁺ may be involved in the contractile activity of cardiac muscle perfused with Ca⁺⁺-free solutions.

Key Words: cardiac contractile activity • Ca and cardiac contractility excitation-contraction coupling • Ca-Na antagonism • toad • lizard • tortoise • chelating agents (EDTA), TEAC and cardiac contractility

Submitted on July 5, 1963