氯菊酯和溴氰菊酯对大鼠血清及脑甲状腺激素水平的影响

目的探讨拟除虫菊酯对大鼠甲状腺激素（TH）水平的影响。方法经口连续１５d给予大鼠氯菊酯（PM）１００、２００、４００mg·kg－１·d－１和溴氰菊酯（DM）６．２５、１２．５０、２５．００mg·kg－１·d－１。用放射免疫分析法检测大鼠血清、脑组织及其亚细胞结构中的TH水平。结果（１）PM：２００、４００mg·kg－１·d－１组大鼠血清三碘甲腺原氨酸（T３）、四碘甲腺原氨酸（T４）、游离T３（fT３）、游离T４（fT４）均下降，而促甲状腺激素（TSH）上升，且现PM呈现剂量依赖关系（T４：r＝０．６７９，fT４：r＝０．５１１，TSH：r＝０．７３８，均P＜０．０１）；１００mg·kg－１·d－１组大鼠T４和fT４下降，T３、fT３、TSH无明显变化。３个处理组大鼠大脑皮层T４分别为（３９．９±５．０）、（３３．４±９．２）、（３２．３±８．２）pg／mgpro，明显低于对照［（４４．２±７．１）g／mgpro］，且有剂量依赖性（r＝０．５２９，P＜０．０１）；而PM染毒４００mg·kg－１·d－１组的T３［（２１．２±５．２）pg／mgpro比对照［（３０．９±１０．０）pg／mgpro］明显降低。２００、４００mg·kg－１·d－１组大鼠海马T４为（１９．１±５．５）、（１９．２±６．５）pg／mgpro，T３为（３

Effects of pyrethroids on the concentrations of thyroid hormones in the rat serum and brain

OBJECTIVE: To investigate the effects of pyrethroids on the concentrations of thyroid hormone in rat brain. METHOD: Permethrin (PM) and deltamethrin (DM) were administered to the rats with daily doses of 100, 200 and 400 mg.kg-1.d-1 and 6.25, 12.5 and 25 mg.kg-1.d-1, respectivelly for 15 days. Serum and brain tissue determinations of thyroxin (T4) and triiodothyronine (T3) were performed by radioimmunoassay (RIA). RESULTS: PM induced a dose dependent decrease in the serum levels of T4, T3, fT4 and fT3 and an increase in the serum TSH levels, whereas DM was only able to induce a dose dependent decrease in the serum levels of T4. PM treatment reduced both the levels of T4 and T3 in homogenates of the cerebral cortex and hippocampus respectively, whereas the highest dose of DM decreased only the cerebral cortex levels of T4. The effects of subchronic treatment with PM and DM on the concentrations of T3 were further investigated in the subcellular fractions, namely nuclei, mitochondria, myelin and synaptosomes of the cerebral cortex and hippocampus. PM treatment induced a decrease in the nuclear and synaptosomal concentrations of T3 of either the cerebral cortex or hippocampus, whereas DM reduced the levels of T3 especially in the mitochondria of the cortex and hippocampus. CONCLUSIONS: Treatment with pyrethroids subchronically to the rats would affect the serum and brain tissue levels of T4 and T3. These results indicate that the pyrethroids-induced neurotoxicity may involve at least in part an impairment of the physiological action of T3 at its subcellular targets.