Modulating effect of ginseng saponins on heterologously expressed HERG currents in Xenopus oocytes.

To examine the effects of ginseng saponins on the heterologously expressed human ether-a-go-go related gene (HERG) that encodes the rapid component of the delayed rectifier K+ channel. A two-electrode voltage clamp technique was used. HERG currents were recorded in Xenopus oocytes injected with HERG cRNA. Crude saponins of Korean red ginseng (GS) induced a minimal increase of the maximal HERG conductance without changes in the voltage-dependent HERG current activation and inactivation curves. GS, however, decelerated HERG current deactivation in a concentration-dependent manner, which was more noticeable with panaxitriol (PT) than panaxidiol (PD). Consistently, ginseng saponins increased the HERG deactivation time constants with the order of potency of Rg1 (a major component of PT)>Rf1>Rb1 (a major component of PD). Re had little effect on HERG deactivation. During a cardiac action potential, GS increased the outward HERG current. Ginseng saponins enhance HERG currents, which could be in part a possible mechanism of the shortening cardiac action potential of ginseng saponins.