罗布麻叶提取物对离体大鼠胸主动脉环的舒张作用

目的:研究罗布麻叶提取物(extracts from leaves of Apocynum venetum,ELA)对离体大鼠胸主动脉环的作用及其可能的机制。方法:采用累积加药法,观察ELA对苯肾上腺素(PE)预收缩的主动脉环张力的影响;观察hemoglobin,亚甲蓝(MB)预处理对ELA扩血管作用影响;观察左旋硝基精氨酸甲酯盐酸盐(L-NAME),甲基异硫脲硫酸盐(SMT)预处理对ELA的扩血管作用的影响;观察四乙胺(TEA),4-氨基吡啶(4-AP)和格列苯脲(GLB)对ELA的血管舒张作用的影响;采用Ca2+剥夺和复加法,观察ELA对细胞内钙释放和外钙内流所引起的血管环收缩反应的作用。结果:ELA可显著舒张PE预收缩的主动脉环,低浓度下(1×10-6～3×10-4)g.mL-1为内皮依赖性作用,而高浓度下(3×10-4,1×10-3)g.mL-1则为内皮非依赖性舒张。低浓度下(1×10-6～3×10-4)g.mL-1,ELA的扩血管作用可被Hemoglobin,MB(P<0.05)和L-NAME,SMT(P<0.05)阻断。高浓度下(3×10-4～3×10-3)g.mL-1,ELA可显著抑制细胞内钙释放和细胞外钙内流(P<0.05);钾通道阻滞剂TEA,4-AP和格列苯脲可不同程度地阻断ELA扩血管作用。结论:ELA可剂量依赖性的舒张PE预收缩的胸主动脉环,呈现低浓度下内皮依赖、高浓度下内皮非依赖的特点。低浓度下ELA的血管舒张作用可能与NO释放有关,高浓度下其作用需要Ca2+,K+通道参与。

Vasodilator Responses of Extracts from Leaves of Apocynum venetum on Thoracic Aorta of Rats

Objective : To investigate the vascular effects of extracts from leaves of Apocynum venetum (ELA) and its mechanisms. Method : Phenylephrine(PE) was used to contract isolated rat thoracic aorta. Concentration relaxation curve of ELA (1× 10^-6-3×10^-3 g·mL^-1) was constructed in cumulative doses manner. Moreover, vasodilator effects of ELA were re-determined after pre-incubated with several antagonists. Result : ELA showed significant vasodilator properties. At low concentration, vascular effects of ELA were inhibited by hemoglobin, methylene blue(MB), NG-nitro-L-arginine methyl ester (L-NAME) and S-methylisothiourea sulfata (SMT). At high concentration, Ca²⁺-induced contraction was suppressed by ELA. In addition, the K⁺ channel blocking agents tetraethylammonium (TEA), 4-aminopyridine (4-AP) and glibenclamide (GLB) inhibited the vasodilator responses of ELA. Conclusion : ELA showed vasodilator effects with property of endothelium-dependency at low concentration and endothelium-independency at high concentration. At low concentration, the vasodilator response of ELA was related to the release of NO, but at high concentration, this action may be associated with Ca²⁺ and K⁺.