Expression of hypoxia inducible factor-1α and erythropoietin in the rat model of brain ischemic tolerance

Objective:To investigate the expression of hypoxia inducible factor-1α(HIF-lα) and erythropoietin (EPO) in the rat model of brain ischemic tolerance induced by ischemic preconditioning(IP). Method: Ninety nine healthy wistar rats were randomly assigned into three groups for different preconditioning, the sham surgery group(SS+SS,n=9),the sham and middle cerebral artery occlusion group(SS+MCAO, n=45),and the ischemic preconditioning and MCAO group(IP+MCAO ,n=45). The latter two groups were further divided into five subgroups respectively for different preconditioning-ischemia intervals. For ischemic preconditioning, the rats were given MCAO for 10min. On 1,3,7,14 and 21d after IP, the rats were given the second MCAO(or sham surgery) for 2h followed by 22h reperfusion. The protein of HIF-1α and EPO were detected by method of immunohistochemistry. The expression of HIF-1α mRNA and EPO mRNA were detected by reverse transcriptase polymerase chain reaction. Result: ①Compared with each of the SS+MCAO subgroups,the expression of HIF-1α protein in the 1d, 3d and 7d subgroups of IP+MCAO and the expression of EPO protein in the 3d and 7d subgroups of IP+MCAO were significantly higher (P0.05,P0.01=. ②The expression of EPO mRNA and HIF-1α mRNA in the 3d ,7d subgroups of IP+MCAO group increased distinctly compared with that of the SS+MCAO group(P0.05=.⑶The expression of EPO mRNA were positively correlated with the expression of HIF-1α mRNA(r=0.737, P0.01). Conclusion:Endogenously produced HIF-lα and EPO may be essential mediators of cerebral ischemic tolerance.