Innate Immunity and Stress and Reproductive Hormone Metrics for Southern Beaufort Sea Polar Bears, 2013-2015

Hair and blood samples were collected from subadult and adult polar bears captured on the sea ice of the southern Beaufort Sea. Hair samples were stored in plastic bags from the point of collection until analysis. Blood samples were stored in the field in coolers with heating pads that prevented freezing during field operations. At the end of the day, blood samples were centrifuged and the serum was removed and blood and hair samples were immediately frozen. All samples were transported frozen from the field to the USGS office in Anchorage, Alaska, where they were put into long-term storage in -80C freezers until the time of analysis.

Hair and blood samples were analyzed to determine hormone concentrations as described by others (Davenport et al. 2006, MacBeth et al. 2012), and hormone concentrations in serum were measured using a protocol modified from Moore (1986). Blood serum samples were analyzed to determine urea and creatinine concentrations to derive urea:creatinine. Cortisol concentrations in hair were validated for radioimmunoassay, however, the samples were previously measured via enzyme immunoassay (Salimetrics, State College, PA) following the manufacturer’s instructions, and those data were used for statistical analysis in the present study. Reproductive hormones were both validated and measured via radioimmunoassay. Validation used pooled samples for hair and serum (small amounts of several samples were combined into one sample for the validation), and tested for parallelism, interference, and matrix effect. Samples were assayed in duplicate, and separate assays were used to measure each reproductive hormone. The intra- and inter-assay coefficients of variation were calculated for each reproductive hormone for both the validation and sample assays. Estimates of urea and creatinine were derived from blood samples using a Vetscan VS2 analyzer, and quality control methods included the use of blanks and comparison of sample duplicates. Measures of innate immunity from blood biomarkers (bactericidal ability, lysis, reactive oxygen species, and oxidative barrier) were determined using established methods (French and Neuman-Lee 2012, Beaulieu et al. 2014, Matson et al. 2005, Schafer and Buettner 2001). Use of land in summer/fall was determined using the methods described in Atwood et al. (2017).