Thyroid hormones and deiodinase activity in plasma and tissues in relation to high levels of organohalogen contaminants in East Greenland polar bears (Ursus maritimus)

• Published in: Environmental Research
• Main Authors: Møller Gabrielsen, Kristin, Obregón, María Jesús, Munro Jenssen, Bjørn
• Other Authors: Danish Cooperation for Environment in the Arctic, Ministerio de Economía y Competitividad (España), Norwegian University of Science and Technology, Comunidad de Madrid
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2015
• Subjects: Arctic; Greenland; East Greenland; Ursus maritimus
• Online Access: http://hdl.handle.net/10261/125126; https://doi.org/10.1016/j.envres.2014.09.019; https://doi.org/10.13039/501100003329; https://doi.org/10.13039/100012818

et al. 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. The field work was funded by the Danish Co-operation for Environment in the Arctic (DANCEA). The analysis of thyroid hormones and deiodinase activitites in tissues was supported by research grants SAF2012-32491 from MINECO and S2010/BMD-2423 from CAM, Spain. This study was funded by NTNU. Peer Reviewed