一氧化氮和内皮素对肝硬化大鼠离体内脏血管条舒缩的影响

目的:探讨一氧化氮(NO)和内皮素(ET)血管活性作用的动静脉差异在门脉高压形成机制中的意义。方法:以四氯化碳皮下注射复制大鼠肝硬化门脉高压模型,取动物门静脉(PV)和肠系膜动脉(MA)制成螺旋血管条,观察NO和ET的最大舒缩反应(Rmax,Cmax),并计算得到EC50值。结果:模型组(n=8)大鼠PV和MA对NO的Rmax显著高于对照组(n=7),EC50显著低于对照组(P<0.05,P<0.01);而对ET的Cmax则显著低于对照组,EC50显著高于对照组(P<0.05,P<0.01)。两组大鼠对NO和ET的最大舒缩反应和EC50,在PV和MA之间均存在显著差异,但模型组相差的幅度显著大于对照组(P<0.05或P<0.01)。结论:NO和ET在肝硬化大鼠内脏血管的舒缩作用存在动静脉差异,这可能是它们参与门脉高压形成的重要因素。

Effects of nitric oxide and endothelin on relaxation and contraction of isolated splanchnic vascular strips in cirrhotic rats

AIM: To investigate the different vasoactive effects of nitric oxide (NO) and endothelin (ET) on splanchnic arterial and venous vessels in cirrhotic rats. METHODS: Cirrhosis was induced in Wistar rats by subcutaneously administration of carbon tetrachloride. Maximal relaxation (Rmax) and contraction (Cmax) to NO and ET were determined in vitro using isolated vascular strips prepared from portal vein (PV) and mesenteric artery (MA) of both cirrhotic and normal rats, and EC50 was calculated for effects of NO and ET, respectively. RESULTS: Rmax of PV and MA to sodium nitroprusside (SNP) (releasing NO) were significantly higher in cirrhotic rats (n=8) than those in normal rats (n=7), and EC50 of NO were dramatically lower in cirrhotic rats than those in control (P<0.05,P<0.01). Cmax of PV and MA to ET were significantly decreased in cirrhotics compared with control, and EC50 of ET were obviously increased in cirrhotic rats compared with normal rats (P<0.05,P<0.01). Furthermore, there were significant differences in Rmax, Cmax and EC50 to NO and ET between PV and MA in both of cirrhotic and normal rats, but these differences in cirrhotics were greater than those in control (P<0.05 or P<0.01). CONCLUSION: There are significant different vasoactive effects of NO and ET on splanchnic arterial and venous vessels in cirrhotic rats, and it may play a crucial role in the pathogenesis of portal hypertension.