AIM: To investigate the role of renin-angiotensin system (RAS) disequilibrium in hyporeactivity and injury of aorta after tourniquet shock ( TS) by observing the changes of aortic contractile reactivity and RAS components after TS.METHODS:Male C57BL/6 mice (8 months old) were divided into 7 groups including control group and 6 mod-el groups.The mice in model groups were sacrificed at reperfusion of 10 min, 1 h, 2 h, 4 h, 6 h and 12 h.The mice in control group were not subjected to tourniquet ligation .The Doppler flowmetry was used to determine the limb blood flow . The carotid artery catheter was applied to detect the blood pressure .The isolated vascular tension tester was available to measure the reactivity of the aorta .HE staining combined with transmission electron microscopy was used to evaluate the morphology of injured aortas .The protein expression of AT 1 receptor , Mas receptor , ACE and ACE2 was measured by Western blot.The serum contents of Ang Ⅱand Ang (1-7) were detected by ELISA.RESULTS:Compared with control group, the blood flow in model groups decreased gradually with the prolongation of reperfusion time .The blood pressure in-creased at 10 min after reperfusion, and then decreased gradually.Accordingly, vascular reaction to norepinephrine (NE) in-creased at 10 min and then descended .The vascular reactivity reached the lowest level at 4 h.Morphological injury score in-creased gradually .Vascular AT1 receptor and ACE2 proteins were reduced , while Mas receptor and ACE proteins were up-regulated compared with control group .The content of AngⅡin the serum elevated, while the content of Ang (1-7) was re-duced.CONCLUSION:The mechanism of aortic reaction to NE increased temporarily in the early stage of shock and then decreased .It may be related to the morphological injury of aorta and the imbalance of RAS .