Blood-based biomarkers of selenium and thyroid status indicate possible adverse biological effects of mercury and polychlorinated biphenyls in Southern Beaufort Sea polar bears.

Abstract We examined biomarkers of selenium status (whole blood Se; serum Se; glutathione peroxidase activity) and thyroid status (concentrations and ratios of thyroxine, T4; tri-iodothyronine, T3; albumin) in polar bears to assess variations among cohorts, and relationships to circulating concentrations of contaminants. Concentrations of total mercury (Hg) in whole blood were similar among cohorts (prime aged males and females, older animals, ages ≥16 years, and young animals, ages 1–5 years; 48.44±35. 81; p =0.253). Concentrations of sum of seven polychlorinated biphenyls (∑PCB 7 ) in whole blood were greater in females (with and without cubs, 26.44±25.82 ng/g ww) and young (26.81±10.67 ng/g ww) compared to males (8.88±5.76 ng/g ww, p p p =0.019; albumin, males, 4.34±0.34 g/dl, females, 4.10±0.29 g/dL, p =0.018). Glutathione peroxidase activity ranged from 109.1 to 207.8 mU/mg hemoglobin, but did not differ significantly by sex or age ( p >0.08). Thyroid hormones were greater in females (solitary females and females with cubs) compared to males ( p p 7 ( p 7 in solitary females ( p =0.045). These data suggest that female polar bears were more susceptible to changes in blood-based biomarkers of selenium and thyroid status than males. Further classifications of the physiologic states of polar bears and repeated measures of individuals over time are needed to accurately assess the biological impact of combined toxicant exposures.