Interaction of selenium and lead on several aspects of thyroid function in Pekin ducklings

Lead shot recovered at necropsy 2 and 3 weeks after being dropped down the throats of Pekin ducklings caused significant increases in thyroid gland weight and 24-hr thyroid uptake of 125I while serum PB125I levels were maintained at or above control values. Supplementation of lead shot with 1 ppm selenium in drinking water reduced these increases. Selenium in the drinking water incurred no increase in thyroid gland weight at 2 weeks but some goitrogenicity at 3 weeks and significant reductions in thyroid radioiodine uptake and serum PB125I levels at 2 and 3 weeks. Chromatographic analyses of thyroid hydrolysates demonstrated a depression in iodothyronine (T4 and T3) labeling in lead shot-treated and selenium-treated animals which was corrected by addition of selenium to lead shot-treated ducklings. These findings indicate that while either lead or selenium treatment, independently, exerts a selective toxic effect on thyroid function, selenium supplementation of lead-treated Pekin ducklings does protect against the toxicity of lead on thyroid function.