[Inhibition of guan-fu base A on delayed rectifier current (Ik) in guinea pig ventricular myocytes]

Guan-fu base A (GFA) is a terpenoid alkaloid isolated from the tuber of Aconitum coreanum, which has been shown to prolong cardiac repolarization in vivo and in vitro. In the present study, the effects of GFA on the delayed rectifier current (Ik) were investigated using the whole cell patch-clamp technique in isolated guinea pig ventricular myocytes. In the presence of CdCl2 100 mumol.L-1, Ik was observed upon depolarizing pulses to +50 mV from a holding potential -40 mV for variable duration (550, 1100, 1650, 2200, 2750, 3300, 3850 ms). The magnitude of Ik after a 2200 ms pulse was 293 +/- 90 pA prior to drug and 227 +/- 59 pA in the presence of GFA 100 mumol.L-1. In a 3850 ms pulse, the magnitude of Ik decreased from 290 +/- 90 to 231 +/- 66 pA after exposure to GFA. The inhibitory effects of GFA on Ik was not dependent on the duration of depolarization. The inward rectifier current (Ik1) was not affected by GFA 100 mumol.L-1. It is concluded that GFA has inhibitory effects on Ik, which may contribute to its prolongation of cardiac repolarization.