中文摘要：

目的：观察尾部悬吊模拟失重时大鼠腹主动脉舒张反应性与一氧化氮合酶表达的影响。方法：体重300～330g的20只雄性SD大鼠按体重配对随机分为对照组与模拟失重组，模拟失重大鼠采用尾部悬吊方法模拟失重。4周后，利用离体动脉血管环舒张实验与Western blot蛋白免疫印迹方法观察了腹主动脉舒张反应性和腹主动脉一氧化氮舍酶eNOS（endothelial NOS）和iNOS（inducible NOS）的表达。结果：悬吊大鼠腹主动脉环时左旋精氨酸（L—Arg）与乙酰胆碱（Ach）的舒张反应显著低于对照，而对硝普钠（SNP）与环磷酸鸟苷（eGMP）的舒张反应在两组间无显著不同。其敏感性在两组间均无显著差别。腹主动脉的eNOS与iNOS表达在模拟失重组与对照组阃亦未发现显著差别。结论：本工作提示尾部悬吊模拟失重下大鼠腹主动脉舒张反应的减弱可能是动脉血管内皮功能改变的结果，尤其是NOS活性的变化可能更为重要。

英文摘要：

Aim： To investigate the effects of simulated microgravity on dilatory responsiveness and NOS expression of abdominal aorta in rats. Mehods： Twenty male healthy SD rats, which body weight ranged from 300 g to 330 g, were divided into control group and simulated micogravity group randomly. After 4 weeks, uing isolated arterial rings from rats, arterial dilatory responsiveness of abdominal aorta were examined in vitro. And the expression of nitric oxide synthase （NOS）, including endothelial NOS （eNOS） and in-ducible NOS （iNOS）, were observed by Western blot. Results： Dilatory responses of arterial rings to L-Arginin （10^-8 -- 10^-3 mol/ L）, and Acetylcholine mol/L） were decreased in simulated microgravity rats compared with that of controls; but dilatory responses of isolated aortic rings to sodium nitroprusid（mol/L） and 8-bromo-cGMP（mol/L） were similar in both simulated microgravity rats and control, rats. The expression of both eNOS and iNOS had not showed significant differences between two groups. Conlusion： The data indicate that endothelium dependent vasorelaxation in abdominal aortic rings are decreased by 4-week simulated microgravity, and this change may be result from altered NOS activity in endothelium.