PARADOXICAL ACTIONS OF QUINIDINE IN HYPERPERMEABLE HEART-CELLS

The effect of quinidine on the inotropic state was examined using small fragments of hyperpermeable ventricular muscle in vitro. In concentrations of 10-5 and 10-4 M, quinidine had no effect on the force of spontaneously contracting fibers. At a concentration of 10-3 M, contractile force increased by at least twofold. We conclude that the negative inotropic action of quinidine is not by a direct action on intracellular organelles of the heart. © 1979 Raven Press, New York.