Vasodilative Ettects Of The Water Extract Of The Rheum Palmatum Linne On Rat Thoracic Aorta And Its Mechanisms

Purpose:The objective to explore the effect of the water extract of Rheum palmatum linne on contraction or relaxation of rat thoracic endothelium-intact and endothelium-dunuded vascular rings and to investigate underlying mechanisms.Methods:The perfusion model of thoracic aortaring of rats was established in vitro to observe the dialative effects of water extract of the Rheum palmatum Linne for integrated endothelium intact or denuded vascular ring preconstricted by1.OWnol/L phenylephrine(PE).The nitric oxide synthase inhibitor Nω-nitro-L-arginine methy ester(L-NAME), guanylyl cyclase inhibitor methylene blue, cyclooxygenase inhibitor indomethacin, calciumactivated potassium channel blocker tetrathyl ammonium(TEA), ATP-sensitive potassium channel bloker glibenclamide and voltage dependent potassium channel blocker4-aminopyridine(4-AP)were used to the effects of vasodilation of water extract of the Rheum palmatum Linne.Results:The water extracts of Rheum palmatum Linne had no significant effets on aortic rings with intact endothelium preconstricted with phenylphrine(PE), while accumulated the water extract of the Rheum palmatum Linne enhance the contraction markedly. Howeher accumulated water extract of the Rheum palmatum Linne had no significant effcts on endothelium dunuded aortic rings in resting tension or with phenylphrine (PE). When the endothelium duneded aortic rings were incubated with wather extract of the Rheum palmatum Linne (0.1mg/mL), contraction elicited by phenylphrine (PE) were not inhibited. Incubation with the Rheum palmatum Linne din’t inhibit contraction elicited by phenylphrine (PE) via Ca2+release and Ca2+influx in the ehdothelium duneded aortic rings. Vasorelaxation effects of Rheum palmatum Linne were endothelium-independent, but L-NAME,metylen blue(MB), indomethacin, glibenclamide and4-aminopyridine did not attenuate the relaxation reponses of the water extracts of Rheum palmatum Linne. In the absence of tetraethylmmonium(1mM), pre-incubation of thr aortic rings with the water extracts of Rheum palmatum Linne significantly reduced the contraction by phenylphrine(PE)Conclusions:These results suggest that the endothelium-independent relaxation in via both voltage operative Ca2+channel blockage and K+channel activation in the water extracts of Rheum palmatum Linne.