Isolation and characterization of single canine cardiac purkinje cells

Single cardiac Purkinje cells should permit improved control of membrane potential during voltage clamp studies. We have developed a method for isolation of single canine Purkinje cells and studied their basic electrophysiological properties using conventional single and double microelectrode techniques. The single Purkinje cells appeared free of connective tissue, had regular striations, excluded trypan blue vital stain, and remained quiescent in solutions containing 1.8 mM calcium. Electrophysiological studies at 22 degrees C showed normal resting membrane potentials, and action potentials could be elicited by extracellular or intracellular stimulation. Plot of the upstroke velocity of the action potential (Vmax) vs. the holding potential showed a sigmoid curve with the peak mean Vmax of 167 V/sec, and voltage corresponding to half-maximal Vmax was about -70 mV. Plot of the overshoot of the action potential vs. the holding potential was similar, with maximal values of about +30 mV. The mean membrane input resistance was 21 M omega and the mean membrane capacitance was 360 pF. These experiments demonstrate that single Purkinje cells have electrical properties similar to intact Purkinje fibers and that they should be useful for more detailed electrophysiological experiments.