title: Thyroid hormones and deiodinase activity in plasma and tissues in relation to high levels of organohalogen contaminants in East Greenland polar bears (Ursus maritimus).
abstract: Previous studies have shown relationships between organohalogen contaminants (OHCs) and circulating levels of thyroid hormones (THs) in arctic wildlife. However, there is a lack of knowledge concerning the possible functional effects of OHCs on TH status in target tissues for TH-dependent activity. The relationships between circulating (plasma) levels of OHCs and various TH variables in plasma as well as in liver, muscle and kidney tissues from East Greenland sub-adult polar bears (Ursus maritimus) sampled in 2011 (n=7) were therefore investigated. The TH variables included 3.3',5.5'-tetraiodothyronine or thyroxine (T4), 3.3',5-triiodothyronine (T3) and type 1 (D1) and type 2 (D2) deiodinase activities. Principal component analysis (PCA) combined with correlation analyses demonstrated negative relationships between individual polychlorinated biphenyls (PCBs) and their hydroxylated (OH-) metabolites and T4 in both plasma and muscle. There were both positive and negative relationships between individual OHCs and D1 and D2 activities in muscle, liver and kidney tissues. In general, PCBs, OH-PCBs and polybrominated dipehenyl ethers (PBDEs) were positively correlated to D1 and D2 activities, whereas organochlorine pesticides and byproducts (OCPs) were negatively associated with D1 and D2 activities. These results support the hypothesis that OHCs can affect TH status and action in the target tissues of polar bears. TH levels and deiodinase activities in target tissues can be sensitive endpoints for exposure of TH-disrupting compounds in arctic wildlife, and thus, tissue-specific responses in target organs should be further considered when assessing TH disruption in wildlife studies.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. Electronic address: kristiga@bio.ntnu.no.
authors.forename: Kristin Møller
authors.initials: KM
authors.lastname: Gabrielsen
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Julie Stene
authors.initials: JS
authors.lastname: Krokstad
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; Division of Mental Health, Department of Child Development and Mental Health, Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, 0473 Oslo, Norway.
authors.forename: Gro Dehli
authors.initials: GD
authors.lastname: Villanger
authors.affiliation: Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, Ontario, Canada K1A 0H3; Department of Chemistry, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
authors.forename: David A D
authors.initials: DA
authors.lastname: Blair
authors.affiliation: Instituto de Investigaciones Biomedicas, Centro Mixto from CSIC-UAM, 28029 Madrid, Spain.
authors.forename: Maria-Jesus
authors.initials: MJ
authors.lastname: Obregon
authors.affiliation: Department of Bioscience, Arctic Research Centre, Aarhus University, Roskilde, P.O. Box 358, DK-4000, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Sonne
authors.affiliation: Department of Bioscience, Arctic Research Centre, Aarhus University, Roskilde, P.O. Box 358, DK-4000, Denmark.
authors.forename: Rune
authors.initials: R
authors.lastname: Dietz
authors.affiliation: Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, Ontario, Canada K1A 0H3; Department of Chemistry, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Letcher
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. Electronic address: bmj@bio.ntnu.no.
authors.forename: Bjørn Munro
authors.initials: BM
authors.lastname: Jenssen
mesh_terms: D000818:Animals; D006116:Greenland; D006219:Halogens / Q000032:analysis* / Q000633:toxicity; D007453:Iodide Peroxidase / Q000097:blood / Q000378:metabolism*; D009930:Organic Chemicals / Q000032:analysis* / Q000633:toxicity; D013963:Thyroid Hormones / Q000097:blood / Q000378:metabolism*; D001503:Ursidae; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity
chemical_list: D006219:Halogens; D009930:Organic Chemicals; D013963:Thyroid Hormones; D014874:Water Pollutants, Chemical; D007453:Iodide Peroxidase
keywords: Deiodinase activity; East Greenland; Organohalogen contaminants; Polar bears; Thyroid hormones