In Vitro Assay Shows That PCB Metabolites Completely Saturate Thyroid Hormone Transport Capacity in Blood of Wild Polar Bears (Ursus maritimus)

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• 作者：Arno C. Gutleb ; Peter Cenijn ; Martin van Velzen ; Elisabeth Lie ; Erik Ropstad ; Janneche Utne Skaare ; Tina Malmberg ; Å ; ke Bergman ; Geir W. Gabrielsen ; Juliette Legler
• 刊名：Environmental Science & Technology
• 出版年：2010
• 出版时间：April 15, 2010
• 年：2010
• 卷：44
• 期：8
• 页码：3149-3154
• 全文大小：173K
• 年卷期：v.44,no.8(April 15, 2010)
• ISSN：1520-5851

文摘

Persistent chemicals accumulate in the arctic environment due to their chemical reactivity and physicochemical properties and polychlorinated biphenyls (PCBs) are the most concentrated pollutant class in polar bears (Ursus maritimus). Metabolism of PCB and polybrominated biphenyl ether (PBDE) flame-retardants alter their toxicological properties and these metabolites are known to interfere with the binding of thyroid hormone (TH) to transthyretin (TTR) in rodents and humans.

In polar bear plasma samples no binding of [¹²⁵I]-T₄ to TTR was observed after incubation and PAGE separation. Incubation of the plasma samples with [¹⁴C]-4-OH-CB107, a compound with a higher binding affinity to TTR than the endogenous ligand T₄ resulted in competitive binding as proven by the appearance of a radio labeled TTR peak in the gel. Plasma incubation with T₄ up to 1 mM, a concentration that is not physiologically relevant anymore did not result in any visible competition.

These results give evidence that the binding sites on TTR for T₄ in wild living polar bears are completely saturated. Such saturation of binding sites can explain observed lowered levels of THs and could lead to contaminant transport into the developing fetus.