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Thyroid hormones and deiodinase activities in plasma and tissues from East Greenland polar bears (Ursus maritimus) during winter season

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Abstract

Thyroid hormones (THs) are essential for metabolism and thermoregulation in arctic animals. Still, there is a lack of deeper basic knowledge regarding the regulation and functioning of THs in the environmental physiology of polar bears (Ursus maritimus). This is necessary in order to understand the true impact and consequences of the combination of stressors such as depletion of sea ice and endocrine-disrupting contaminants for the polar bear species. As a first step to gain insight into TH physiology in polar bears, TH concentrations in liver, kidney and muscle in East Greenland polar bears sampled February–March 2011 were analysed and their associations with circulating levels of THs were investigated. In addition, type 1 deiodinase (D1) activities in liver, kidney and muscle and type 2 deiodinase (D2) activities in muscle were analysed. Concentrations of 3,5,3′,5′-tetraiodothyronine (T4) were highest in plasma, followed by liver, kidney and muscle, whereas concentrations of 3,5,3′-triiodothyronine (T3) were highest in kidney followed by liver, plasma and muscle. D1 activities in the tissues varied in the order liver > kidney ≫ muscle, while D2 activity was only analysed in muscle. There were significant positive relationships between T4 in plasma and liver as well as between T4 in plasma and D1 activity in liver. This implies that liver is an important non-thyroidal organ for deiodination of T4, thus providing T3 to the plasma pool, in polar bears. The polar bears with the lowest body condition also had the lowest concentrations of free T3 in plasma and D2 activities in muscle.

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Acknowledgments

The field work for this study was funded by the Danish Co-operation for Environment in the Arctic (DANCEA). The analyses of thyroid hormones and deiodinase activities in tissues were supported by research Grants SAF2012-32491 from MINECO and S2010/BMD-2423 from CAM, Spain. The authors thank all those who contributed to the field work in the Scoresby Sound area in East Greenland, including the local hunters who provided the polar bears for this study through their aboriginal hunting quotas. The authors would also like to thank Sigga Joensen and Rune Dietz at Aarhus University for performing the ageing of the polar bears and Grethe Stavik Eggen at NTNU for help with the thyroid hormone analysis in plasma. The study was funded by the Norwegian University of Science and Technology (NTNU).

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Authors and Affiliations

  1. Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, Norway

    Kristin Møller Gabrielsen, Julie Stene Krokstad, Gro Dehli Villanger & Bjørn Munro Jenssen

  2. Instituto de Investigaciones Biomedicas, Centro Mixto from CSIC-UAM, 28029, Madrid, Spain

    Maria-Jesus Obregon

  3. Department of Bioscience, Arctic Research Centre, Aarhus University, P.O. Box 358, 4000, Roskilde, Denmark

    Christian Sonne & Rune Dietz

  4. Department of Child Development and Mental Health, Norwegian Institute of Public Health, P.O. Box 4404, 0473, Nydalen, Oslo, Norway

    Gro Dehli Villanger

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  1. Kristin Møller Gabrielsen
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Correspondence to Kristin Møller Gabrielsen or Bjørn Munro Jenssen.

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Gabrielsen, K.M., Krokstad, J.S., Obregon, MJ. et al. Thyroid hormones and deiodinase activities in plasma and tissues from East Greenland polar bears (Ursus maritimus) during winter season. Polar Biol 38, 1285–1296 (2015). https://doi.org/10.1007/s00300-015-1694-z

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