title: Thyroid disruption in male goldfish (Carassius auratus) exposed to leachate from a municipal waste treatment plant: Assessment combining chemical analysis and in vivo bioassay.
abstract: Several classes of thyroid-disrupting chemicals (TDCs) have been found in refuse leachate, but the potential impacts of leachate on the thyroid cascade of aquatic organisms are yet not known. In this study, we chemically analyzed frequently reported TDCs, as well as conducted a bioassay, to evaluate the potential thyroid-disrupting effects of leachate. We used radioimmunoassay to determine the effects of leachate exposure on plasma 3,3',5-triiodo-l-thyronine (T3), 3,3',5,5'-l-thyroxine (T4), and thyroid-stimulating hormone (TSH) levels in adult male goldfish (Carassius auratus). We also investigated the impacts of leachate treatment on hepatic and gonadal deiodinases [types I (D1), II (D2), and III (D3)] and gonadal thyroid receptor (TRα-1 and TRβ) mRNA expressions by using real-time polymerase chain reaction. The results indicated the presence of five TDCs (bisphenol A, 4-t-octylphenol, di-n-butyl phthalate, di-n-octyl phthalate, and diethylhexyl phthalate); their mean concentrations in the leachate were 18.11, 2.76, 4.86, 0.21, and 9.16 μg/L, respectively. Leachate exposure induced plasma T3 and TSH levels in male fish, without influencing the plasma T4 levels. The highly elevated D2 mRNA levels in the liver were speculated to be the primary reason for the induction of plasma T3 levels. Disruption of thyroid functions by leachate was also suggested by the up-regulation of D1 and D2 as well as TRα-1 mRNA levels in the gonads. Prominent thyroid disruptions despite the very low TDC concentrations in the exposure media used in the bioassay strongly indicated the existence of unidentified TDCs in the leachate. Our study indicated the necessity of conducting in vivo bioassays to detect thyroid dysfunctions caused by leachate.
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Tian
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China.
authors.forename: Xiaona
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China. Electronic address: weiwang@ouc.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Marine Life Science College, Ocean University of China, Qingdao 266003, China. Electronic address: rusg@ouc.edu.cn.
authors.forename: Shaoguo
authors.initials: S
authors.lastname: Ru
mesh_terms: D000818:Animals; D001681:Biological Assay; D003993:Dibutyl Phthalate / Q000633:toxicity; D006054:Goldfish / Q000502:physiology*; D006066:Gonads / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D010795:Phthalic Acids / Q000633:toxicity; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D013961:Thyroid Gland / Q000187:drug effects*; D013972:Thyrotropin / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D015854:Up-Regulation; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D003993:Dibutyl Phthalate; D010795:Phthalic Acids; D012333:RNA, Messenger; D013972:Thyrotropin; D014284:Triiodothyronine; D062065:Wastewater; D014874:Water Pollutants, Chemical; C010715:di-n-octyl phthalate
keywords: Chemical analysis; Deiodinase; Refuse leachate; Thyroid hormones; Thyroid receptors; Thyroid-disrupting chemicals