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(506) Do Thyroid Hormone Levels Indicate Stress from Environmental Pollutants in Nestling Bald Eagles?
Bowerman, William*,1, Susan, Lombardini2, Refsal, Kent2, Sikarskie, James2, Croisant, Emma3, Grasman, Keith3, 1 Clemson University, Pendleton, SC, USA2 Michigan State University, East Lansing, MI, USA3 Wright State University, Dayton, OH, USA
ABSTRACT- It has been proposed that levels of thyroid hormones measured in plasma of birds are indicative of stress caused by environmental toxicants, particularly planar halogenated compounds. In order to test this hypothesis we conducted both a field experiment using nestling bald eagles (Haliaeetus leucocephalus) and a controlled laboratory study using leghorn chickens. Nestling eagles were sampled during an ongoing contaminant monitoring project. Up to 12 cc of blood was drawn from the brachial vein using asceptic techniques. Plasma was centrifuged and stored in liquid nitrogen. Fertilized, leghorn chicken eggs were unexposed or injected with 0, 0.100, 0.175, 0.250 or 0.325 ng/g of PCB 126 in sunflower oil into the air cell. Plasma was collected at 5 weeks of age and stored at -80C until analysis. Total T3, Total T4, and Free T4 were determined using radioimmunoassay kits. Using previously determined subpopulations based on exposure to PCBs and p,p'-DDE, we analyzed results from nestling eagles. No significant relationship was found between location and Total T4 levels. Significant differences were found for both Total T3 (p=0.0008) and Free T4 (0.0589) among subpopulations with nestlings from Great Lakes>Lower Michigan>Voyageurs NP>Upper Michigan for Total T3 and Voyageurs NP>Upper Michigan>Great Lakes>Lower Michigan for Free T4. These differences did not follow a dose-response relationship. No significant differences in Total T3, Total T4 or Free T4 were found among the dose groups and controls for the chicken experiment. Based on the results of this chicken experiment, none of the thyroid hormone levels (Total T3, Total T4, Free T4) appear to be useful biomarkers of PCB toxicity. However, this was an in ovo exposure and endpoints were not measured until 5 weeks post-hatch.
Key words: thyroid hormones, bald eagle, chicken, biomarker
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