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


METHODS
A two-electrode voltage clamp technique was used. HERG currents were recorded in Xenopus oocytes injected with HERG cRNA.


RESULTS
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.


CONCLUSIONS
Ginseng saponins enhance HERG currents, which could be in part a possible mechanism of the shortening cardiac action potential of ginseng saponins.
Kim
Cuk-seong
CS
Department of Physiology, College of Medicine, Chungnam National University, Daejeon 301-131, Korea. jinbong@cnu.ac.kr.
Son
Sook-jin
SJ
Kim
Hyo-shin
HS
Kim
Yong-duk
YD
Lee
Kyu-seung
KS
Jeon
Byeong-hwa
BH
Kim
Kwang-jin
KJ
Park
Jin-kyu
JK
Park
Jin-bong
JB
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D036145:Ginsenosides / Q000302:isolation & purification / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects* / Q000378:metabolism; D005894:Panax / Q000737:chemistry; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*; D014982:Xenopus laevis
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D036145:Ginsenosides; C000606913:KCNH2 protein, human; D024642:Potassium Channels, Voltage-Gated; C442759:ginsenoside Rb1; C055328:ginsenoside Rf; C035054:ginsenoside Rg1