桑叶乙酸乙酯提取物的血管作用及其机制

目的:探讨桑叶乙酸乙酯提取物对离体大鼠胸主动脉环收缩张力的作用及其机制。方法:采用生物信号采集系统记录灌流胸主动脉环张力变化。结果:①桑叶乙酸乙酯提取物(0.25~32.0 g/L)对苯肾上腺素(PE,1-0 6m o l/L)和KC l(6×1-0 2m o l/L)预收缩的内皮完整和去内皮的血管环均有舒张作用,且呈浓度依赖性;②EC50(KC l 6 g/L,PE 6.4 g/L)的桑叶乙酸乙酯提取物可使CaC l2量效曲线下移,最大反应降低;③经钙通道阻断剂维拉帕米预处理的去内皮血管,桑叶乙酸乙酯提取物可加强PE引起的血管收缩,与ryanod ine受体阻断剂钌红共孵育可取消维拉帕米的上述作用,而IP3受体阻断剂肝素则不能取消其作用。结论:桑叶乙酸乙酯提取物对血管呈非内皮依赖性的双重作用,其舒张效应大于收缩效应。桑叶乙酸乙酯提取物产生的血管舒张作用可能是通过抑制电压依从性钙通道和受体依从性钙通道减少Ca2 内流入血管平滑肌细胞所致;其收缩作用可能是通过激活内质网ryanod ine受体,引起内质网内Ca2 释放引起的。

Vascular effect of extract from mulberry leaves and underlying mechanism

Objective: To investigate the vascular activity of extract from mulberry leaves(EML) on rat thoracic aorta and the underlying mechanism.Methods: Isolated thoracic rings of Sprague-Dawley rats were mounted on the organ bath and the tension of the vessel was recorded.Results:(1)EML produced a concentration-dependent vasorelaxation of aorta preconstricted by high K~( )(60 mmol/L) or 10~(-6)mol/L phenylephrine(PE) in endothelium-intact and endothelium-denuded arteries.(2)EML at EC_(50) concentration reduced the calcium dose-response curve.(3)After incubation of aorta with verapamil,EML induced vasocontraction of aorta preconstricted by PE,which was abolished by ruthenium red.Conclusions: The vascular effect of EML is biphasic,the vasorelaxation is greater than the vasocontraction.The vasorelaxation induced by EML may be mediated by inhibition of voltage-and receptor-dependent calcium channels in vascular smooth muscle cells,while the vasocontraction is via activation of ryanodine receptor in endoplasmic reticulum.