Abstract: Objective To study there lation ship bewteen serumreproductive horm one level and expression of caspase-3 in sperma to genic cell in rats with manganese exposure.Methods Forty eight male rats were randomly divided into one control group and two mang anese chloride(MnCl₂)(15,30 mg/kg)exposure groups.After exposed to manganese for 4 and 6 weeks,the serum testoste rone(T),follicle stmiulating bormone(FSH),and luteinizine hormone(LH)levels were detected with radiomimunoassay.The expression of caspase 3 in spermatogenic cells was detected with mimunoh isto chemical methods (SABC).Results The levels of T,FSH and LH in 30 mg/kg MnCl₂ groups were 2.78±0.74 nmol/L,0.44±0.03 U/L,0.19±0.02 U/L for rats wtih 4 weeks exposure and 2.76±0.81 nmol/L,0.57±0.03 U/L,0.19±0.02 U/L for rats with 6 weeks exposure,respectively.The percentages of caspase-3 positive cell were 65.49±11.34 and 82.65±5.26 for rats with 4 weeks and 6 weeks of mangan sesexposure,respectively.There existed anegative correlation between the caspase-3 positive cell rate and serum level of T(r=0.799,P<0.01).There existed a positive correlation bewteen the caspase-3 positive cell rate and serum levels of FSH and LH(r=0.735,P<0.01;r=0.737,P<0.01).Conclusion The decrease of serum T and the increases of serum FSH and LH may be the miportant causes of the up regulation of caspase-3 expression in spermatogenic cells in rats exposed to manganese.