Effects of Viscum coloratum flavonoids on fast response action potentials of hearts

The effects of the total flavonoids of Viscum coloratum (VCF) on the fast response action potentials (FAP) of canine Purkinje fibers and guinea pig ventricular papillary muscles were studied by glass-microelectrode technique. The effects of VCF on the ionic currents through cellular membrane were analysed with selective ion blockers (CsCl, verapamil, and TEA+), respectively. VCF (100 micrograms.ml-1) accelerated the repolarization of FAP and increased delta ERP/delta APD ratio, which were related to decreasing Isi and increasing Ix. It was suggested that the anti-tachyarrhythmic mechanism of VCF was attributed to prolonging ERP relatively and to abolishing reentrant excitation.