Effect of 2,4 dinitrophenol on electrical activity in Purkinje and ventricular muscle fibers of hog heart.

• Fn a recent study, it was observed that 2,4. dinitrophenol, in concentrations of 2 to 5 X 10~ M, produced a shortened action potential duration and a decrease in the amplitude of the action potential in the atrial fiber of the isolated mouse heart and in the ventricular fibers of the intact and isolated perfused frog heart. The membrane resting potential was unchanged even during the period of cardiac arrest. Similar findings had been reported in the rat atrium and cat ventricular muscle fiber/' In the study reported here, the investigation was extended to the specialized conductive (Purkinje) fiber in order to make comparative observations of the effects of 2,4 dinitrophenol on the electrical activity of this fiber as compared to its effect on ventricular muscle fiber. A false tendon-ventricular muscle preparation of the hog heart was used because its greater mass compared to a frog heart preparation facilitated visualization and employment of the technical procedures suitable for this study.