RESUMO
AIM:To observe the effect of angiotensin-converting enzyme 2(ACE2)deletion on vasoconstric-tion reactivity of aortic segments in ACE2 knockout(KO)mice with tourniquet shock(TS).METHODS:The 8-month-old male mice with C57BL/6 background were divided into wild-type(WT)control group,WT-TS group,KO group and KO-TS group,with 10 mice in each group,of which five were used for determination of vascular reactivity,and the other five for the other assays.The hindlimbs of the mice in WT-TS group and KO-TS group were ligated with tourniquet for 2 h and loosened for 4 h.The mice in WT group and KO group were subjected to the same treatment except for tourniquet liga-tion.The vasoconstriction reactivity of the aorta was measured on tensiometer.The morphological damage of the aorta was evaluated by vascular histopathology.Western blot was used to detect the expression of AT1,MAS,ACE and ACE2 pro-teins in aorta.The serum levels of angiotensin(Ang)Ⅱ and Ang-(1-7)were determined by enzyme-linked immunosorbent assay.RESULTS:Compared with WT group,the mice in WT-TS group had lower vascular reactivity to norepinephrine(NE)and obvious vascular lesions.The expression of ACE protein increased significantly(P＜0.01),while the expres-sion of ACE2 decreased(P＜0.05).The expression of AT1 protein in aorta decreased significantly,the expression of MAS protein increased significantly,and the AT1/MAS ratio decreased(P＜0.01).Serum Ang II level increased,serum Ang-(1-7)level decreased,and Ang Ⅱ/Ang-(1-7)ratio increased(P＜0.05).Compared with WT group,vascular reactivity in KO group increased at low concentration of NE(＜10-7 mol/L),and decreased at high concentration(＞10-7 mol/L)without vascular lesion.The expression levels of aortic AT1,MAS and ACE were all elevated(P＜0.05).The serum level of Ang Ⅱ increased(P＜0.05),but the level of Ang-(1-7)had no obvious change.Compared with KO and WT-TS groups,the aortic reactivity in KO-TS group subtracted apparently(P＜0.05),representing its curve shifting to the right obviously.The morphological damage aggravated slightly,and the expression of AT1 and ACE increased slightly in KO-TS group com-pared with WT-TS group(P＜0.05).However,the expression of MAS increased significantly in vascular tissue(P＜0.01).The serum levels of Ang Ⅱ and Ang-(1-7)further increased and decreased,respectively,and the Ang Ⅱ/Ang-(1-7)ratio increased(P＜0.01).CONCLUSION:Deficiency of ACE2 induces severe aortic hyporeactivity to NE during TS,which may be related to the increased imbalance of renin-angiotensin system in ACE2 gene knockout mice.
RESUMO
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 .