中文摘要：

目的：探讨RhoA调节失血性休克大鼠血管反应性的机制。方法：采用SD大鼠复制休克模型，取离体血管环，观察Rho激酶、肌球蛋白轻链磷酸酶（MLCP）、肌球蛋白轻链磷酸激酶（MLCK）对RhoA增加血管反应性的作用；同时取原代血管平滑肌细胞（VSMCs），观察RhoA对缺氧后VSMCRho激酶、MLCP和MLCK活性的调节作用以及对肌球蛋白轻链（MLC20）磷酸化水平的影响。结果：失血性休克后大鼠肠系膜上动脉（SMA）对NE收缩反应性明显降低，RhoA的激动剂U-46619可明显升高休克后血管反应性，RhoA特异性抑制剂C3酶可拮抗U-46619所引起的血管收缩反应性的升高。Rho激酶抑制剂Y-27632可降低由U-46619所引起的血管反应性的升高，MLCP的抑制剂CMyculin可进一步增加由U-46619所引起的血管反应性的升高，而MLCK抑制剂对U-46619的作用影响不明显。缺氧后MLCK、Rho激酶活性以及MLC20磷酸化水平明显降低，MLCP活性明显升高，RhoA激动剂U-46619可明显升高缺氧后VSMC的MLC。磷酸化水平、Rho激酶活性和降低MLCP的活性，且U-46619的这一作用可被RhoA抑制剂C3酶所拮抗，调节RhoA的活性对MLCK活性无明显调节作用。结论：RhoA可通过Rho激酶调节MLCP活性和MLC加磷酸化水平调节休克后血管反应性。

英文摘要：

AIM： To observe the mechanisms of RhoA on vascular reactivity following hemorrhagic shock （HS） in rats. METHODS： The superior mesenteric artery （SMA） in rats subjected to hemorrhagic shock was adopted to assay the vascular reactivity via observing the contraction initiated by norepinephrine （NE） with isolated organ perfusion system. Meanwhile, the effects of Rho kinase, myosin light chain phosphatase （MLCP）, myosin light chain kinase （ML- CK） on RhoA regulating vascular reactivity were observed. The effects of RhoA agonist U -46619 and inhibitor C3 enzyme on the activities of Rho kianse, MLCP, MLCK and phosphorylation of MLC20 in the vascular smooth muscle cells （VSMC） with hypoxia were also measured. RESULTS： As compared to control group, the cumulative dose - response curves of SMA to NE at 2 h after shock shifted to the right, the maximal contractions （ Emax ） of NE was significantly decreased. RhoA agonist U -46619 increased the vascular reactivity in the late period of shock. C3 enzyme abolished U -46619 induced the increase in the contractile response of SMA to NE. Rho kinase inhibitor Y - 27632 decreased U - 46619 - induced the increase in the vascular reactivity, MLCP inhibitor calyculin further promoted the increase in the vascular reactivity. However, MLCK inhibitor had no effect on the U -46619 -induced change of vascular reactivity. After hypoxia, the activities of Rho kinase and MLCK, and the level of MLC20 phosphorylation were decreased, MLCP activity was increased. RhoA agonist U- 46619 increased the activity of Rho kinase and phosphorylation of MLC20, decreased the activity of ML- CP, but had no effects on MLCK activity. CONCLUSION： RhoA plays an important role in the regulation of vascular reactivity following shock. The mechanism is closely related to regulating the activities of Rho kinase and MLCP, and increasing the phosphorylation of MLC20 in VSMC.