EFFECTS OF TETRANDRINE ON THE SLOW INWARD CURRENTS IN CANINE CARDIAC PURKINJE FIBERS

Effects of tetrandrine (Tet) on the slow inward currents in canine cardiac Purkinje fibers were studied by using two-microelectrode voltage clamp technique. Tet was shown to inhibit the peak value of the slow inward current (I_si PV) in dose-dependent and time-dependent manners. After pretreatment with Tet 30 and 100 μmol/L for 10 min, respectively, the I_si PV decreased from 47.90±5.6 nA and 38.4±21.5 nA to 21±7.8 nA and 6.3±7.7 nA (p<0.01). I_si PV induced by strontium instead of calcium ions was also significantly reduced after exposure to Tet 100 μmol/L. The results suggest that Tet is a slow channel blocker.