RESUMO
Objective To investigate the effect of low dose of BDE209 on thyroid hormone and thyroid hormone metabolism enzyme-iodothyroninedeiodinases Ⅱ(D2) in off spring mice after pregnancy exposure .Methods Total 64 adult SPF female Kun-ming mice were randomly divided into 4 groups ,which treated with oral gavage of 0 ,50 ,100 ,300 μg · kg -1 · d-1 dose of BDE209 after successful pregnancy ,the exposure continue to 21 days after delivery .10 mice was randomly selected in each offspring group and get the peripheral blood and brain sample ,the serum thyroid hormones level ,oxidative damage and the expression of D2 mRNA in brain were detected .Results Compared with the control group(0μg · kg -1 · d-1 dose of BDE209) ,the TT4 ,TT3 ,FT4 and FT3 levels of offspring mice increased significantly in every exposure group (P< 0 .05);antioxidant enzyme glutathione-S transferees (GST) ,superoxide dismutase (SOD) activity decreased with the BDE209 dose increase (P<0 .05) ,and malondialdehyde (MDA) level increased (P<0 .05);the D2 mRNA relative expression of brain in middle(100μg · kg -1 · d-1 dose of BDE209) and high(300μg · kg -1 · d-1 dose of BDE209) dose group decreased when compared with control group (P< 0 .05) .Conclusion Low level of BDE209 exposure in pregnancy resulted in the increasing of thyroid hormone levels in offspring mice ,which may cause oxidative damage and decrease expression of D2 mRNA in the brain .