Reference intervals for blood-based biochemical analytes of southern Beaufort Sea polar bears

Abstract

Accurate reference intervals (RIs) for commonly measured blood-based analytes are essential for health monitoring programmes. Baseline values for a panel of analytes can be used to monitor physiologic and pathophysiologic processes such as organ function, electrolyte balance and protein catabolism. Our reference population includes 651 serum samples from polar bears (Ursus maritimus) from the southern Beaufort Sea (SB) subpopulation sampled in Alaska, USA, between 1983 and 2016. To establish RI for 13 biochemical analytes, we defined specific criteria for characterizing the reference population and relevant subgroups. To account for differences in seasonal life history characteristics, we determined separate RI for the spring and fall seasons, when prey availability and energetic requirements of bears differ. We established RI for five subgroups in spring based on sex, age class and denning status, and three subgroups in fall based on sex and age class in females only. Alkaline phosphatase activities were twice as high in subadult as in adult polar bears in spring (zmales = 4.08, Pmales < 0.001, zfemales = 3.90, Pfemales < 0.001) and did not differ between seasons. Denning females had significantly higher glucose concentrations than non-denning females (z = 4.94, P < 0.001), possibly reflecting differences in energy expenditure during lactation. A total of 10 of the 13 analytes differed significantly between seasons in either males or females; however, the physiologic importance of these differences may be minimal. Establishing these RIs allows for temporal monitoring of polar bear health in the SB and may prove useful for assessing and monitoring additional polar bear subpopulations in a changing Arctic environment.

Long‐term assessment of relationships between changing environmental conditions and the physiology of southern Beaufort Sea polar bears (Ursus maritimus)

“…We also observed annual changes in biomarkers linked to liver function. In clinical veterinary medicine, small increases in liver enzyme activity are often masked by wide reference intervals (Fry et al, 2019) with pathologic concerns indicated by at least a twofold or greater change in enzyme activity. Although we did not see multifold increases in ALT, it significantly increased with capture year in both male and female bears (Appendix S2, Figure 6).…”

“…We further explored the extent to which differences in summer habitat selection (i.e., use of land versus sea ice), breeding status of females, and short-term fasting status influenced physiologic biomarkers. Because demographic characteristics of polar bears and season affect physiology (Atwood, Peacock, et al, 2016;Derocher et al, 1990;Fry et al, 2019; Kirk et al, 2010a;Rode et al, 2017;Rode, Regehr, et al, 2021;Whiteman et al, 2015Whiteman et al, , 2018, we included sex, age, and denning status, as well as season of capture and year as co-variates in our analysis.…”

“…Frozen sera were transported to the laboratory and stored at −70°C until analyzed. All serum samples were analyzed on the same VetScan VS2 biochemistry analyzer (Abaxis, Union City, California) using a comprehensive diagnostic panel commonly used to assess general physiologic health in animals (Fry et al, 2019; Thrall et al, 2012). The panel included measurements of the following analytes: alanine aminotransferase (ALT), alkaline phosphatase (ALP), albumin (ALB), blood urea nitrogen (BUN), calcium (Ca), creatinine (CREA), phosphorus, sodium, and total protein (TP).…”

“…For some samples, only a subset of these analytes was available. The functional and interpretive characteristics of the biomarkers evaluated are summarized in Table 1 (recreated from Fry et al, 2019). The long-term stability of stored blood samples can be a concern in retrospective studies.…”

Physiological implications of life at the forest interface of oil palm agriculture: blood profiles of wild Malay civets (Viverra tangalunga)

“…We suggest it is unlikely there is evidence of age-driven variation in Malay civet renal performance, as urea levels did not vary with animal age, as would be clinically expected from renal complications. Similar patterns were documented in Iberian lynx ( Beltrán et al, 1991 ; García et al ., 2010 ), Amur leopard ( Bodgener and Lewis, 2017 ), polar bear ( Ursus maritimus, Fry et al, 2019 ) and Chinese pangolin ( Manis pentadactyla, Khatri-Chhetri et al, 2015 ).…”