Interaction of Epinephrine and Ouabain on Automaticity of Canine Purkinje Fibers

Abstract

The interaction of ouabain and epinephrine on diastolic depolarization of canine Purkinje fibers was studied using conventional microelectrode techniques. When the Purkinje fibers were treated with ouabain alone, they developed slow diastolic depolarization accompanied by a proportionate decrease in the maximum diastolic potential. When these digitalized Purkinje fibers were further treated with epinephrine, the rate of these changes was greatly accelerated, resulting in rapid spontaneous activity in some Purkinje fibers. The rate of development of increased automaticity observed in the preparations treated with both ouabain and epinephrine was two to three times faster than that observed in the preparations exposed to ouabain alone. Epinephrine alone at the same concentration caused minimal changes in diastolic depolarization of these preparations. Propranolol in a beta-receptor blocking dose prevented the potentiating effect of epinephrine but did not interfere with the effect of ouabain on diastolic depolarization of Purkinje fibers. It is concluded that epinephrine potentiates the ouabain-induced increase in automaticity of Purkinje fibers by stimulating beta receptors.