Abstract: Objective To study the effects and significance of manganese on the expression of Caspase-3 and Ki-67 in sperm atogenic cells of malerats.Methods Forty-eight male rats were randomly divided in to 6 groups(2 blank control groups,2,15mg/kg MnCl₂,and 30mg/kg MnCl₂ groups)and were exposed to manganese(MnCl₂H₂O)by I.P.for 4 and 6 weeks,respectively and blank control group was in jected with NS.All rats were injected once everyday,five tmies per week.In the 4 th and 6th weekend,their testis were collected for examination.The expression of Caspase 3 and Ki 67 intestis were determined by immunoh istochemical methods(SABC).Results Compared with blank control group,the Caspase-3-positive cell rate in all exposure groups were increased significantly(P<0.01).Among manganese exposure groups of same dose,the Caspase-3 positive cell rate of 6wks exposure groups was increased significantly than those in 4wks exposure groups(P<0.01).Among exposure groups of same tmie,the Caspase-3 positive cell rate of 30mg/kg MnCl₂ group was increased significantly than those of 15mg/kg MnCl₂ group(P<0.01).Compared with blank control group,the Ki 67 positive cell rate in 15mg/kg MnCl₂ 4wks group was decrea sed(P<0.05),those of 15mg/kg MnCl₂-6wks group,30mg/kg MnCl₂ 4wks group and 30mg/kg MnCl₂ 6wks group were much lower(P<0.01).Among exposure groups of same dose,the Ki-67 positive cell rate of 15mg/kg MnCl₂-6wks group was decreased significantly compared with that of 15mg/kg MnCl₂ 4wks group(P<0.01).Among exposure groups of same tmie,the Ki-67 positive cell rate of cells in 30mg/kg MnCl₂ group was decreased significantly than that of 15mg/kg MnCl₂ group(P<0.01).There existed a negative correlation between Caspase-3 positive cell rate and Ki-67 positive rate(r=-0.798,P<0.01).Conclusion 15mg/kg MnCl₂ exposure for 4wks could promote the expression of Caspase-3 and inhibit the expression of Ki-67 in ratsperma to genic cells with dose effect and tmie effect relation ship.Itmay be an important mechanism of spermatogenic dy sfuction