Abstract: ObjectiveTo observe apoptosis related cell morphology,biochemical changes and phosphrylations of phosphoralated extracellularc signal-regulated kinase(p-Erk)in pheochromocytoma cells(PC12)exposed to manganese at different concentration and exposure time.MethodsPC12 cells in logarithm growth period were incubated in culture media with 200,400,600,and 800μmol/L manganese(MnCl 2)for 1,2,3 and 4 days,respectively.The cell viability was examined with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrasolium bromide(MTT)and morphological changes of PC12 cells were investigated with transmission electron microscope.Agarose gel electrophoresis was adopted to detect the genomic DNA of Mn-treated PC12 cells.Western blot was used to test p-Erk in manganese-treated PC12 cell at different time and concentration of the exposure.ResultsManganese at different concentrations could suppress the proliferation of PC12 cells in doseand time-dependent manner at 1,2,3,4 days,respectively.The cell inhibited ratio on the fouth day in 600μmol/L MnCl 2 group approached 50% or more and the apoptosis was observed with transmission electron microscope as well as biochemical hallmark of DNA fragments.The results of western blot showed that the phosphorylation of Erk of PC12 cells exposed to 600μmol/L MnCl₂ increased gradually on the 1st,2nd,3rd,and 4th day,respectively.The activation of Erk on the 3rd day was 6.6 times higher than that of control group(n=3,P<0.05).The phosphorylation of Erk was enhanced by the exposures of 200,400,and 600μmol/L MnCl₂ in PC12 cells within 4 days.The activation of Erk of 400μmol/L MnCl₂ treated group at the 4th day was 4.7 times higher than that of control group(n=3,P<0.05).ConclusionThe neuron toxicity of manganese could induce apoptosis in PC12 cells by down-regulaton of p-Erk.