Changes of vascular endothelial growth factor and angiopoietin-1 expression in the rat model of brain ischemic tolerance induced by transient ischemia preconditioning

Objective To study the effects of focal ischemia preconditioning on vascular endothelial growth factor(VEGF)and angiopoietin-1(Ang-1)expression.Methods Wistar rats were randomly assigned to three groups:sham surgery(n=9),non-ischemic preconditioning(NIP,n=45),and ischemic preconditioning(IP,n=45).For IP,the rats were given middle cerebral artery occlusion for 10 minutes.In the NIP group,pre-ischemia was replaced by sham surgery.Subsequently,the latter two groups were equally divided into five subgroups according to time of first reperfusion,including 1d,3d,7d,14d and 21d subgroups.The models were evaluated with examinating neurologic deficit scores and infarct.The expression VEGF and Ang-1 protein were determined by immunohistochemical staining.Results(1)Intergroup comparison:Compared with the NIP group,neurologic deficit scores and infarct volume significantly decreased on 1d,3d,7d in subgroups of IP group(P0.05,P0.01).The expression of VEGF protein of 1d,3d,7d subgroups and Ang-1 protein of 7d subgroups significantly increased in the rat cerebral cortex and corpus striatum in the ischemic hemisphere of IP group.(2)In the IP group:Infarct volume significantly decreased in the1d,3d,7d subgroups(P0.05).The expression of VEGF protein on 3d and 7d significantly increased compared with other groups(P0.05).Conclusion IP induced cerebral ischemic tolerance and increased expression of VEGF,and Ang-1 induced by IP might play an important roles in process of brain ischemic tolerance.