黄芪的内皮依赖性血管舒缩作用及其机制

目的　黄芪有一定的治疗高血压作用 ,本研究观察其对大鼠离体胸主动脉环舒缩的影响 ,并探讨其可能机制。方法　采用大鼠离体主动脉环灌流模型 ,观察累积浓度黄芪 (0 .0 1～ 10 0g·L- 1)对基础状态、KCl预收缩和去氧肾上腺素 (PE)预收缩的血管环的作用。结果　黄芪 (0 .0 1～ 10 0g·L- 1)对基础状态或KCl预收缩的内皮完整血管环张力无影响。对PE预收缩的内皮完整血管环 ,黄芪在低浓度 (0 .0 1～ 3.0g·L- 1)时呈浓度依赖性舒张作用 ,此作用可被一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(0 .1mmol·L- 1)或鸟苷酸环化酶抑制剂亚甲蓝 (10μmol·L- 1)预处理所抑制 ;而在高浓度 (10～ 10 0g·L- 1)时呈短暂的收缩作用 ,可被内皮素转换酶抑制剂磷阿米酮 (5 μmol·L- 1)预处理所抑制。黄芪对PE预收缩的去除内皮血管环仅呈微弱的浓度依赖性舒张作用。结论　黄芪对主动脉具有内皮依赖性舒缩双相作用。其舒张机制可能为激活血管内皮细胞一氧化氮 鸟苷酸环化酶途径 ;而其收缩机制可能为促进血管内皮合成内皮素。

Astragalus membranaceus induced endothelium-dependent vasomotor effect and its mechanism in rat thoracic aortas

AIM To study why Astragalus membranaceus (AM) can be used as a hypotensive, the vasomotor effect of AM on rat thoracic aorta rings and the underlying mechanism were investigated. METHODS AM 0.01－100 g·L^-1 was cumulatively added into organ bath. Isometric tension of endothelium-intact or denuded thoracic aorta rings in basal tension, preconstricted by KCl or phenylephrine (PE), respectively, was recorded. RESULTS Cumulative administration of AM 0.01－100 g·L^-1 did not affect the vasomotion of aortic rings with endothelium either in basal tension or preconstricted by KCl. Exposure of endothelium intact rings precontricted by PE to AM at low concentration (0.1－3.0 g·L^-1) induced a significant concentration dependent relaxation, which was inhibited by preincubation with N^ω-nitro-L-arginine methyl ester or methylthioninium chloride. But at the high concentration (10－100 g·L^-1), AM transiently potentiated the PE evoked contraction that can be reversed by phosphoramidone. Moreover, a weak vasorelaxant response to AM in endothelium-denuded rings precontracted by PE was observed. CONCLUSION AM has endothelium-dependent diphasic effects of relaxation and contraction on aorta rings. The effect of relaxation may be mediated by the NO-guanylyl cyclase pathway, while the contration may be related to endothelin release.