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目的研究五溴联苯醚(BDE-99)对大鼠甲状腺结构和功能的影响。方法将健康清洁级4周龄SD大鼠40只随机分为溶剂对照(玉米油)组和低(30mg/kg)、中(60mg/kg)和高(120mg/kg)剂量BDE-99染毒组,每组10只。采用灌胃方式进行染毒,染毒剂量为2.5ml/kg体重,连续染毒15d。采用放射免疫法测定游离三碘甲状腺原氨酸(FT3)、游离四碘甲状腺原氨酸(FT4)和促甲状腺素(TSH)的浓度。分别采用二氨基联苯胺(DAB法)和四唑氮(NBT)法对甲状腺过氧化物酶(thyroperoxidase,TPO)和琥珀酸脱氢酶(succinate dehydro-genase,SDH)的酶组织化学情况进行观察,并采用免疫组化检测和HE染色观察组织病理改变。电镜下观察甲状腺滤泡细胞超微结构改变。结果随着BDE-99染毒剂量的升高,血清FT4、FT3浓度呈降低趋势,而血清TSH浓度则呈升高趋势;甲状腺组织的TPO、SDH活力呈降低趋势,甲状腺组织的PCNA阳性细胞数则呈升高趋势。BDE-99染毒组TPO、SDH显色加深,电镜观察可见甲状腺滤泡细胞胞浆内有大量明显扩张呈囊状的粗面内质网,胞核、胞膜和线粒体未见损伤。结论 BDE-99有可能通过降低甲状腺球蛋白的合成水平而减低甲状腺激素的浓度,反馈性升高TSH浓度,从而导致腺体组织代偿性增生、细胞酶活力增高。
Objective To investigate the effects of pentabromodiphenyl ether (BDE-99) on the thyroid structure and function in rats. Methods 40 healthy 4-week-old Sprague-Dawley rats were randomly divided into two groups: the solvent control (corn oil) group and the low (30mg / kg), middle (60mg / kg) and high (120mg / kg) BDE-99 Group, 10 in each group. The gavage method was used to inoculate, the dose was 2.5ml / kg body weight, continuous exposure for 15d. The levels of free triiodothyronine (FT3), free tetraethionine (FT4) and thyrotropin (TSH) were determined by radioimmunoassay. The enzymatic histochemistry of thyroperoxidase (TPO) and succinate dehydro-genase (SDH) were observed by DAB method and NBT method respectively , And histopathological changes were observed by immunohistochemistry and HE staining. Ultrastructural changes of thyroid follicular cells were observed under electron microscope. Results With the increase of the dose of BDE-99, the concentrations of FT4 and FT3 in serum decreased, while the concentrations of serum TSH increased. The activities of TPO and SDH in thyroid tissue decreased. The number of PCNA positive cells in thyroid tissue It is rising trend. The color of TPO and SDH in BDE-99-treated group deepened. Electron microscopy showed a large number of cytoplasm in the follicular cells of thyroid follicles with a large number of rough endoplasmic reticulum, no damage of nucleus, cell membrane and mitochondria. Conclusions BDE-99 may reduce thyroid hormone concentration by decreasing the synthesis level of thyroglobulin, and increase the TSH concentration retrospectively, resulting in the compensatory proliferation of glandular tissue and the increase of the cellular enzyme activity.