title: Transthyretin-binding activity of contaminants in blood from polar bear (Ursus maritimus) cubs.
abstract: We determined the transthyretin (TTR)-binding activity of blood-accumulating contaminants in blood plasma samples of approximately 4-months-old polar bear (Ursus maritimus) cubs from Svalbard sampled in 1998 and 2008. The TTR-binding activity was measured as thyroxine (T4)-like equivalents (T4-EQMeas). Our findings show that the TTR-binding activity related to contaminant levels was significantly lower (45%) in 2008 than in 1998 (mean ± standard error of mean: 1998, 2265 ± 231 nM; 2008, 1258 ± 170 nM). Although we cannot exclude a potential influence of between-year differences in capture location and cub body mass, our findings most likely reflect reductions of TTR-binding contaminants or their precursors in the arctic environment (e.g., polychlorinated biphenyls [PCBs]). The measured TTR-binding activity correlated positively with the cubs' plasma levels of hydroxylated PCBs (OH-PCBs). No such association was found between TTR-binding activity and the plasma levels of perfluoroalkyl substances (PFASs). The OH-PCBs explained 60 ± 7% and 54 ± 4% of the TTR-binding activity in 1998 and 2008, respectively, and PFASs explained ≤1.2% both years. Still, almost half the TTR-binding activity could not be explained by the contaminants we examined. The considerable levels of TTR-binding contaminants warrant further effect directed analysis (EDA) to identify the contaminants responsible for the unexplained part of the observed TTR-binding activity.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, NO-7491 Trondheim, Norway.
authors.forename: Jenny
authors.initials: J
authors.lastname: Bytingsvik
authors.forename: Eszter
authors.initials: E
authors.lastname: Simon
authors.forename: Pim E G
authors.initials: PE
authors.lastname: Leonards
authors.forename: Marja
authors.initials: M
authors.lastname: Lamoree
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lie
authors.forename: Jon
authors.initials: J
authors.lastname: Aars
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Derocher
authors.forename: Oystein
authors.initials: O
authors.lastname: Wiig
authors.forename: Bjørn M
authors.initials: BM
authors.lastname: Jenssen
authors.forename: Timo
authors.initials: T
authors.lastname: Hamers
mesh_terms: D000818:Animals; D001665:Binding Sites; D004785:Environmental Pollutants / Q000378:metabolism*; D011228:Prealbumin / Q000378:metabolism*; D011869:Radioligand Assay; D001503:Ursidae / Q000097:blood*
chemical_list: D004785:Environmental Pollutants; D011228:Prealbumin