Abstract: BACKGROUND AND AIM: To explore the potential mechanisms of neural apoptosis induced by deltamethrin(DM). MATERIAL AND METHODS: PC12 cells were respectively given with 10－4 mol/L, 10－5 mol/L and 10－6 mol/L deltamethrin. Fas, FasL and TNFR1 protein in PC12 cells were qualitatively determined by immunocytochemistry at 24 hours after deltamethrin treatment. Fas, FasL and TNFR1 protein were indirectly marked with fluorescein FITC and their relative contents(rate of positive cells ，RPC and mean fluorescence intensity,MFI) were quantitatively determined with flow cytometry , meanwhile apoptosis of PC12 cells was studied using flow cytometry with PI staining at 24 hours and 48 hours after deltamethrin treatment. RESULTS: Immunostaining for Fas, FasL and TNFR1 protein was found in the control and deltamethrin treatment PC12 cells. But the different expressions of these three proteins were not detected among the control and deltamethrin treatment PC12 cells. Twenty-four hours after deltametrin treatment, we discovered that Fas, FasL protein did not altered but TNFR1 protein increased in cells with 10－5 mol/L and 10－4 mol/L deltamethrin treatment(each MFI was 3.50±0.26,3.74±0.33) opposite to the control(MFI was 2.69±0.19)(P<0.05). Forty-eight hours after cells were exposed to deltematrin , Fas, FasL and TNFR1 protein increased only in cells with 10－4 mol/L deltamethrin treatment(each MFI was 42.85±8.4,37.91±1.65,8.09±1.83) opposite to their own control(each MFI was 29.37±3.07,29.71±0.68,5.30±0.33)(P<0.05). Compared with the control, the apoptotic ratio increased only when the cells were treated with 10－4 mol/L deltamethrin for 48 hours[(0.60± 0.08) ％ vs(2.62±1.37) ％]. And there are correlations between apoptotic ratio and DM，Fas，Fasl protein. CONCLUSIONS: Apoptosis of PC12 cells induced by deltamethrin maybe be mediated by death receptor Fas. 　　

Key words: deltamethrin, Fas protein, FasL protein, TNFR1 protein, apoptosis, flow cytometry