Abstract： Objective To investigate the effects of polybrominated diphenyl ether-153 (BDE-153) exposure during lactation period on the calcium ion (Ca2+) concentration and calcium-activated enzyme levels in cerebral cortical cells among adult rats and to provide a scientific basis for the study on the developmental neurotoxicity of BDE-153.Methods Forty newborn male rats were randomly and equally divided into four groups according to their body weights and litters:1,5,and 10 mg/kg BDE-153 groups and olive oil solvent control group.On postnatal day 10 (PND 10),the BDE-153 groups were administrated BDE-153 (0.1 ml/10 g body weight) by intraperitoneal injection,while the olive oil solvent control group was given an equal volume of olive oil.Two months later,these rats were decapitated,and the cerebral cortex was separated quickly on an ice-cold dish.The Ca2+ concentration in cerebral cortical cells was measured by flow cytometry.The activities of calcineurin (CaN) and Ca2+-Mg2+-ATP enzyme were determined by colorimetric method.The mRNA and protein expression of calpain-1 and calpain-2 was measured by real-time quantitative PCR and Western blot.Results The mean fluorescence intensities of intracellular Ca2+ in control group and 1,5,and 10 mg/kg BDE-153 groups were 10.83,1.48,1.93,and 0.62,respectively; the 1,5,and 10 mg/kg BDE-153 groups had significantly lowerintercellular Ca2+ concentrations than the control group (P＜0.05).The activities of CaN and Ca2+-Mg2+-ATP enzyme and mRNA and protein expression of calpain-1 showed no significant differences between the 1,5,and 10 mg/kg BDE-153 groups and control group (P＞).05).The protein expression of calpain-2 increased as the dose of BDE-153 rose.Compared with the control group (mRNA:0.81±0.26; protein:0.15±0.07),the 5 and 10 mg/kg BDE-153 groups had significantly higher mRNA expression of calpain-2 (5 mg/kg BDE-153 group:1.16±0.52; 10 mg/kg BDE-153 group:1.32±0.23) and significantly higher protein expression of calpain-2 (5 mg/kg BDE-153 group:0.31±0.07; 10 mg/kg BDE-153 group:0.37±0.06) (P＜0.05).The 10 mg/kg BDE-153 group had significantly higher protein expression of calpain-2 than the 1 mg/kg BDE-153 group (0.37±0.06 vs 0.22±0.07,P＜0.05).Conclusion Ca2+mediated calpain-2 activation may be one of the main mechanisms of BDE-153 neurotoxicitv.