Effects of ginsenosides on vascular reactivity in rat cerebral and renal arteries

Objective To investigate possible mechanisms underlying the antioxidant property(1)and the in vitro vasodilator effects(2)of the two ginsenosides,Rb1 and Rg1,in isolated rat renal and cerebral arteries.Methods Arterial rings were mounted in a multi-channel myograph for recording of isometric tension.To examine the antioxidant activity,some rings were exposed to a free radical-generating reaction(hypoxanthine and xanthine oxidase)with and without pre-treatment with ginsenosides.The calcium antagonistic effects were tested on rings contracted by membrane depolarization in elevated extracellular potassium ions,a condition that promoted Ca2+ influx in vascular smooth muscle cells.Results Ginsenosides protected endothelial function(endothelial nitric oxide-dependent relaxation)against oxidative stress;(2)ginsenoside Rb1 reduced the high K+-induced contractions of both renal and cerebral arteries while ginsenoside Rg1 relaxed the rat cerebral artery but not the renal artery.Conclusions Ginsenosides are vaso-protective via(1)the antioxidant activity which protects endothelial cell function and(2)the inhibition of Ca2+ influx through voltage-sensitive Ca2+ channels in vascular smooth muscle.The vasodilator effects may suggest the potential preventive or therapeutic values of ginsenosides against stroke and renal hypertension.