Objective To study the effects of ouabain on
action potential and calcium ion current of myocytes. Methods Action potentials
of papillary muscle in isolated guinea pig and sinoatrial node from rabbits were examined using standard and ion-selective microelectrode techniques. Single ventricular cells were isolated enzymatically. Effect of ouabain on voltage-dependent
calcium current in isolated guinea pig ventricular myocytes was recorded using whole-cell patch clamp techniques. Results 1 μmol·L -1 ouabain shortened APD in papillary muscles of guinea pig and increased rate of diastolic depolarization (RDD) and maximal velocity of phase 0 depolarization(V max) in sinuatrial node.\ 10 μmol·L -1 ouabain induced irregalar rhythm of
action potential in papillary muscle and sinoatrial node.\ Furthermore, 100 μmol·L -1 ouabain induced fluther beats of action potential of papillary muscle and sinoatrial node. 1 and 10 μmol·L -1 ouabain increased while 100 μmol·L -1 decreased the L-type calcium currents. Conclusion Besides its inhibition of Na +/K +-ATPase, ouabain had direct effect on electrophysiology of myocytes.