内皮依赖性超极化因子在剪切应力引起的内皮依赖性舒张反应中的作用

目的研究内皮依赖性超极化因子(EDHF)在剪切应力引起的内皮依赖性舒张反应中的作用及机制。方法测定不同流量下的血管内径及各种内皮依赖性舒张因子抑制剂、钾通道抑制剂、细胞色素P450单氧化酶抑制剂作用下的血管内径。结果剪切应力在大鼠肠系膜微动脉引起的舒张反应是内皮依赖性的,且在大的肠系膜动脉明显大于小阻力型肠系膜动脉。EDHF在上述两种动脉的内皮依赖性舒张反应中作用均明显大于NO,起主要作用。剪切应力引起的内皮依赖性舒张反应不受SKF525A的抑制，ChTx加apamin明显抑制了此舒张反应，TBA则几乎完全抑制此舒张反应。结论在剪切应力引起的内皮依赖性舒张反应中EDHF起主要作用，钾通道特别是K_Ca通道的激活为主要机制。

Role of endothelium-derived hyperpolarizing factor in shear stress-induced endothelium-dependent relaxations of rats

AIM: To investigate the role and mechanism of endothelium-derived hyperpolarizing factor (EDHF) in shear stress induced vasorelaxation of rat mesenteric artery. METHODS: The changes in vessel diameter in response to variable flow (0-300 microL.min(-1)) were continuously examined. The contribution of prostacyclin (PGI2), NO and EDHF to shear stress induced relaxation were analyzed by inhibitory effects of indomethacin, N(G)-nitro-L-arginine (L-NA) and KCl. The nature and hyperpolarizing mechanism of EDHF were examined by the inhibitory effects of inhibitors of cytochrome P450 pathway and of various K+ channels. RESULTS: The shear stress-induced relaxation were endothelium dependent and the contribution of NO was more prominent in large mesenteric arteries (400-500 microm) than that in resistance arteries (150-250 microm), whereas that of EDHF was noted in both-sized blood vessels. Tetrabutylammonium (a nonselective inhibitor of K channels) almost abolished, whereas the combination of charybdotoxin (an inhibitor of both large and intermediate-conductance Ca2+-activated K channels) and apamin (an inhibitor of small-conductance Ca2+-activated K channels) significantly inhibited the EDHF-mediated component of the shear stress-induced relaxations. CONCLUSION: EDHF plays an important role in shear stress-induced endothelium-dependent relaxations, and K channels especially calcium-activated K channels appear to be involved.