Aim To explore the role of heat-shock protein 90 in protective effect of hydrogen sulfide against H9C2 cardiac cells injuries induced by cobalt chloride.Methods H9C2 cells were exposed to cobalt chloride at different doses to set up the chemical hypoxia-induced cardiomyocyte injury model.Sodium hydrosulfide(a hydrogen sulfide donor)was added into cell medium for 30 min before cobalt chloride treatment.Cell viability was tested by using cell counter kit-8.Morphological changes in apoptotic cardiomyocytes were detected by Hoechst 33258 staining and photofluorography.The expression of heat-shock protein 90 was evaluated by Western blot.Results H9C2 cell viability was inhibited by cobalt chloride at the concentrations from 600 to 1000 μmol/L for 24 h in a dose-dependent manner.Pretreatment with 400 μmol/L sodium hydrosulfide 30 min before exposure to cobalt chloride significantly blocked the cardiomyocyte cell injuries induced by cobalt chloride at 600,800 and 1000 μmol/L respectively,leading to an increase in cell viability.Heat-shock protein 90 expression was upregulated after treatment with 400 μmol/L sodium hydrosulfide for 30 min,peaking at 6 h to 9 h,returning to the basal level at 18 h.17-allylamino-17-demethoxygeldanamycin(2 μmol/L),an inhibitor of heat-shock protein 90,not only enhanced H9C2 cells injury induced by cobalt chloride,but also obviously blocked the inhibition of hydrogen sulfide on cobalt chloride-induced cardiomyocyte damage,reducing viability of H9C2 cells,increasing number of apoptotic cells,which didn't damage H9C2 cells alone.Conclusion Hydrogen sulfide can protect H9C2 cells against cobalt chloride-induced injury and upregulate expression of heat-shock protein 90.17-allylamino-17-demethoxygeldanamycin not only increases cobalt chloride-induced H9C2 cell injury,but also significantly inhibits the cardioprotection of hydrogen sulfide,suggesting that heat-shock protein 90 may mediate the cardioprotective effect afforded by hydrogen sulfide.