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This Article Full Text Full Text (PDF) All Versions of this Article: 288/5/R1264    most recent 00793.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Richardson, S. J. Articles by Renfree, M. B. Search for Related Content PubMed PubMed Citation Articles by Richardson, S. J. Articles by Renfree, M. B.

COMPARATIVE AND EVOLUTIONARY PHYSIOLOGY

Developmentally regulated thyroid hormone distributor proteins in marsupials, a reptile, and fish

¹Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria, Australia; ²Department of Biology, University of Bergen, Bergen, Norway; ³Department of Zoology, University of Canterbury, Christchurch, New Zealand; ⁴Centro de Ciências de MAR, Universidade do Algarve, Faro, Portugal; ⁵Department of Zoology, La Trobe University, Bundoora, Victoria, Australia; ⁶Institut für Experimentelle Endokrinologie und Endokrinologisches Forschungs-Centrum der Charité Berlin, Berlin, Germany; ⁷Department of Zoology, University of Melbourne, Parkville, Victoria, Australia

Submitted 23 November 2004 ; accepted in final form 5 January 2005

Thyroid hormones are essential for vertebrate development. There is a characteristic rise in thyroid hormone levels in blood during critical periods of thyroid hormone-regulated development. Thyroid hormones are lipophilic compounds, which readily partition from an aqueous environment into a lipid environment. Thyroid hormone distributor proteins are required to ensure adequate distribution of thyroid hormones, throughout the aqueous environment of the blood, and to counteract the avid partitioning of thyroid hormones into the lipid environment of cell membranes. In human blood, these proteins are albumin, transthyretin and thyroxine-binding globulin. We analyzed the developmental profile of thyroid hormone distributor proteins in serum from a representative of each order of marsupials (M. eugenii; S.crassicaudata), a reptile (C. porosus), in two species of salmonoid fishes (S. salar; O. tshawytsch), and throughout a calendar year for sea bream (S. aurata). We demonstrated that during development, these animals have a thyroid hormone distributor protein present in their blood which is not present in the adult blood. At least in mammals, this additional protein has higher affinity for thyroid hormones than the thyroid hormone distributor proteins in the blood of the adult. In fish, reptile and polyprotodont marsupial, this protein was transthyretin. In a diprotodont marsupial, it was thyroxine-binding globulin. We propose an hypothesis that an augmented thyroid hormone distributor protein network contributes to the rise in total thyroid hormone levels in the blood during development.

transthyretin; thyroxine-binding globulin; albumin