title: Morphological and functional deterioration of the rat thyroid following chronic exposure to low-dose PCB118.
abstract: Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that can severely disrupt the synthesis and secretion of endocrine hormones. To investigate the effects of 2,3',4,4',5-pentachlorobiphenyl (PCB118) on thyroid structure and function, 40 male Wistar rats were divided into 4 equal treatment groups and administered vehicle or one of three doses of PCB118. The experimental groups received intraperitoneal (i.p.) injection of 10, 100, or 1000μg/kg/day PCB118, 5 days per week for 13 weeks, whereas the control group was injected with corn oil (vehicle). Serum concentrations of free thyroxine (FT4), free triiodothyronine (FT3) and thyroid stimulating hormone (TSH) were measured by radioimmunoassays. Histopathological and ultrastructural changes in the thyroid were observed under light microscopy and transmission electron microscopy (TEM). The mRNA expression levels of the sodium-iodide symporter (NIS) and thyroglobulin (TG) were quantified by real-time PCR. Increasing doses of PCB118 resulted in progressively lower FT3, FT4 and TSH concentrations in serum. Injection of PCB118 at all doses led to histopathological deterioration of the thyroid characterized by follicular hyperplasia and expansion, shedding of epithelial cells and fibrinoid necrosis. Follicle cells exhibited swollen or vacuolated endoplasmic reticula, as revealed by TEM. Exposure to PCB118 also caused significant decreases in NIS and TG mRNA expression levels. Chronic exposure to low-dose PCB118 and other PCB congeners may be a significant risk factor for thyroid diseases.
authors.affiliation: Department of Endocrinology, First Affiliated Hospital, Nanjing Medical University, Nanjing, PR China.
authors.forename: Jin-Mei
authors.initials: JM
authors.lastname: Tang
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Xie
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Guo
authors.forename: Pei
authors.initials: P
authors.lastname: Cheng
authors.forename: Huan-Huan
authors.initials: HH
authors.lastname: Chen
authors.forename: Xu-Qin
authors.initials: XQ
authors.lastname: Zheng
authors.forename: Lin
authors.initials: L
authors.lastname: Jiang
authors.forename: Dai
authors.initials: D
authors.lastname: Cui
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.forename: Guo-Xian
authors.initials: GX
authors.lastname: Ding
authors.forename: Yu
authors.initials: Y
authors.lastname: Duan
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D046529:Microscopy, Electron, Transmission; D011078:Polychlorinated Biphenyls / Q000008:administration & dosage / Q000633:toxicity*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D027981:Symporters / Q000096:biosynthesis; D013954:Thyroglobulin / Q000096:biosynthesis; D013961:Thyroid Gland / Q000187:drug effects* / Q000473:pathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D000099209:Sodium-Iodide Symporters
chemical_list: D004785:Environmental Pollutants; D011078:Polychlorinated Biphenyls; D012333:RNA, Messenger; D027981:Symporters; D013954:Thyroglobulin; D013972:Thyrotropin; D013974:Thyroxine; D014284:Triiodothyronine; D000099209:Sodium-Iodide Symporters; C070055:2,3',4,4',5-pentachlorobiphenyl
keywords: Environmental endocrine disruptors; Polychlorinated biphenyls 118; Sodium-iodide symporter; Thyroglobulin; Thyroid hormones; Thyroidal histopathology disturbance