Abstract: Objective To explore the effect of deltamethrin(DM)on gamma-glutamylcysteine synthetase(γ-GCS) activity and reduced glutathione(GSH)content in PC12 cells.Methods PC12 cells were treated with 0,1,10,100 μmol/L DM for 6 hours or 12 hours,respectively.Cytotoxicity of DM on PC12 cells was measured by methyl thiazolyl tetrazolium(MTT)assay.The cytosolic fraction of PC12 cells was used to determine reduced glutathione(GSH)content andγ-GCS activity by reversed-phase high performance liquid chromatographic assay with o-phthalaldehyde pre-column derivatization.Results The survival rate of PC12 cells treated with 100μmol DM for 6 hours or 12 hours was lower than that of control group(P<0.01,P<0.001).In PC12 cells treated for 6 hours,there was no effect onγ-GCS activity and GSH content.In PC12 cells treated for 12 hours,there was no difference inγ-GCS activity and GSH content between low concentration and control group.Theγ-GCS activity of the high concentration group was significantly lower than that in the control group(P<0.05).Conclusion These findings demonstrate thatγ-GCS activity in PC12 cells could be inhibited by high concentration of DM treatment for a long time.