Objective：To explore the ERK1/2 expressions and significances in hypoxia/reoxygenation cardiomyocytes post-processed by H2S. Methods：H9C2 cardiomyocytes were exposed to hypoxia/reoxygenation and then post－processed by H2S. The cardiomyocytes were divided into five groups：hypoxia/reoxygenation group（H/R），hydrogen sulfide post-treatment group（H2S），hydrogen sulfide post-treatment with ERK inhibitor group（H2S+PD），ERK inhibitor group（PD） and control group（control）. The expressions of ERK1/2 mRNA were detected by qPCR，and ERK1/2 protein expressions were detected by Western blot. In each group the proliferation rates of cardiomyocytes were analyzed by CCK-8，and the cell apoptosis rates were analyzed by flow cytometry. Results：There were signifi－cantly statistical differences in expression of ERK1/2 mRNA gene among H2S group，H/R group，H2S+PD group and PD group（F=23.000，P=0.000）. ERK1/2 mRNA was over expressed in rat H9C2 cells in H2S group（P=0.005），more evident in H2S+PD group（0.895±0.106） than in H/R group（P=0.027）. There were significantly statistical differences in expression of ERK1/2 protein among H2S group，H/R group，H2S+PD group and PD group（F1=5.15，P1=0.016，F2=5.44，P2=0.045）. CCK-8 assay showed that of myocardial cell proliferation was significantly increased in H2S group than in the other groups. Flow cytometry results suggested that myocardial cell apoptosis rate was significantly lower in H2S group than in the other groups. Conclusion：ERK1/2 mRNA and protein expressions of hypoxia/reoxygenation cardiomyocytes are significantly increased，with higher proliferation rate and lower apoptosis rate after H2S treatment. Exogenous donor H2S could activate ERK signal pathway，further benefiting the recovery of hypoxia/reoxygena－tion cardiomyocytes and leading to myocardial protection.
