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The previous reports demonstrated that ginseng saponins, active ingredient of Panax ginseng, inhibited blood vessel contraction induced by various hormones or high K+. Recently, we demonstrated that 20(R)- and 20(S)-ginsenoside RG₃ regulate ion channel activities with differential manners. The aim of this study was to examine whether ginsenoside RG₃ isomers also show differential effects on swine coronary artery contractionresponses induced by high K+, serotonin (5-HT) or acetylcholine. Treatment of 20(S)- but not 20(R)-ginsenoside RG₃ caused a concentration-dependent relaxation of coronary artery contracted by 25 mM KCl. 20(S)- and 20(R)-ginsenoside RG₃ induced significant relaxations of coronary artery contraction induced by 5-HT (3 μM) in the presence of endothelium with concentration-dependent manner and, also in the absence of endothelium only 20(S)-ginsenoside RG₃ induced a strong inhibition of coronary artery contraction induced by 5-HT in a concentration-dependent manner. 20(S)-ginsenoside RG₃ caused relaxation of coronary artery in the absence and presence of endothelium. In contrast, treatment of 20(S)- and 20(R)-ginsenoside RG₃ (100 μM) did not show significant inhibition of coronary artery contraction induced by acetylcholine (0.01 to 30 μM) in the presence of endothelium, whereas both isomers caused significant inhibition of coronary artery contraction induced by acetylcholine (0.01 to 30 μM) in the absence of endothelium in a concentration-dependent manner. These findings indicate that 20(S)- or 20(R)-ginsenoside RG₃ exhibits differential relaxation effects of swine coronary artery contractions caused by high K+, acetylcholine, and 5-HT treatment and that this differential vasorelaxing effects of ginsenoside RG₃ isomers also might be dependent on endothelium.
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