Abstract： Objective To explore the possible mechanism that Gadd45a and Egr-1together participate in the DNA damage repair,by analyzing the influence of hepatic ischemia-reperfusion injury (IRI) on the rnRNA and protein expression of hepatic cell cycle-related genes.Method Methods Forty-two SD rats were divided into normal control group,ischemia 30 min group and reperfusion 30 min,1h,2 h,3 h and 24 h groups.The hepatic specimens of rats at the corresponding time points after success of modeling were obtained. Chip experiment was used to screen out the key genes Gadd45a,Egr-1and GAPDH for target genes.We used Northern blot and RT-PCR to confirm the chip's results. The expression of related proteins was detected by using immunofluorescence and immunohistochemistry.Results Northern blot detection results showed that the RT-PCR products and the target genes for testing were concordant.The expression spectral chip signal and RT-PCR detection revealed that the expression of target genes had a 4-fold increase at early reperfusion period (1h) (up-regulation of Egr-1,Gadd45a and HSP70-1a by 9.39,8.28 and10.8 respectively.At the later stage of reperfusion (24 h),the expression of Egr-1,Gadd45a and Hspala was reduced to the normal levels, and the chip screening results were consistent with the RT-PCR test results.Fluorescence immunohistochemistry demonstrated that in the reperfusion1h and 2 h groups,the expression of Egr-1in nuclei of liver cells was positive. Immunohistochemistry indicated that the Gadd45 expression in the nucleus and cytoplasm was gradually increased with increasing reperfusion time.Conclusion Gadd45a and Egr-1are the key genes of the nuclear factor (NF)-kB regulatory pathways,and involved in the regulation of cell cycle arrest at G2/M phase and repair of damaged DNA in rat hepatic IRI.