Enzyme activity and liver tissue PCB concentrations of chicks of northern fulmars (F. glacialis) and black-legged kittiwakes (R. tridactyla) from Kongsfjorden

Arctic seabirds are exposed to a wide range of halogenated organic contaminants (HOCs). Exposure occurs mainly through food intake, and many pollutants accumulate in lipid-rich tissues. Little is known about how HOCs are biotransformed in arctic seabirds. In this study, we characterized biotransformation enzymes in chicks of northern fulmars (Fulmarus glacialis) and black-legged kittiwakes (Rissa tridactyla) from Kongsfjorden (Svalbard, Norway). Phase I and II enzymes were analyzed at the transcriptional, translational and activity levels. For gene expression patterns, quantitative polymerase chain reactions (qPCR), using gene-sequence primers, were performed. Protein levels were analyzed using immunochemical assays of western blot with commercially available antibodies. Liver samples were analyzed for phase I and II enzyme activities using a variety of substrates including ethoxyresorufin (cytochrome (CYP)1A1/1A2), pentoxyresorufin (CYP2B), methoxyresorufin (CYP1A), benzyloxyresorufin (CYP3A), testosterone (CYP3A/CYP2B), 1-chloro-2,4-nitrobenzene (CDNB) (glutathione S-transferase (GST)) and 4-nitrophenol (uridine diphosphate glucuronyltransferase (UDPGT)). In addition, the hydroxylated (OH-) polychlorinated biphenyls (PCBs) were analyzed in the blood, liver and brain tissue, whereas the methylsulfone (MeSO2-) PCBs were analyzed in liver tissue. Results indicated the presence of phase I (CYP1A4/CYP1A5, CYP2B, and CYP3A) and phase II (GST and UDPGT) enzymes at the activity, protein and/or mRNA level in both species. Northern fulmar chicks had higher enzyme activity than black-legged kittiwake chicks. This in combination with the higher XOH-PCB to parent PCB ratios suggests that northern fulmar chicks have a different biotransformation capacity than black-legged kittiwake chicks.

(Table 1) Polychlorinated biphenyl (PCB) and PCB metabolite concentrations in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea

Polychlorinated biphenyls (PCBs) may induce activity of hepatic enzymes, mainly Phase I monooxygenases and conjugating Phase II enzymes, that catalyze the metabolism of PCBs leading to formation of metabolites and to potential adverse health effects. The present study investigates the concentration and pattern of PCBs, the induction of hepatic phase I and II enzymes, and the formation of hydroxy (OH) and methylsulfonyl (CH3SO2=MeSO2) PCB metabolites in two ringed seal (Phoca hispida) populations, which are contrasted by the degree of contamination exposure, that is, highly contaminated Baltic Sea (n = 31) and less contaminated Svalbard (n = 21). Phase I enzymes were measured as ethoxyresorufin-O-deethylation (EROD), benzyloxyresorufin-O-dealkylation (BROD), methoxyresorufin-O-demethylation (MROD), and pentoxyresorufin-O-dealkylation (PROD) activities, and phase II enzymes were measured as uridine diphosphophate glucuronosyl transferase (UDPGT) and glutathione-S-transferase (GST). Geographical comparison, multivariate, and correlation analysis indicated that sum-PCB had a positive impact on Phase I enzyme and GST activities leading to biotransformation of group III (vicinal ortho-meta-H atoms and <=1 ortho-chlorine (Cl)) and IV PCBs (vicinal meta-para-H atoms and <=2 ortho-Cl). The potential precursors for the main OH-PCBs detected in plasma in the Baltic seals were group III PCBs. MeSO2-PCBs detected in liver were mainly products of group IV PCB metabolism. Both CYP1A- and CYP2B-like enzymes are suggested to be involved in the PCB biotransformation in ringed seals.

(Table 1) Concentration of PCB and other contaminants in blood plasma of polar bears (Ursus maritimus) from Svalbard

Persistent chemicals accumulate in the arctic environment due to their chemical reactivity and physicochemical properties and polychlorinated biphenyls (PCBs) are the most concentrated pollutant class in polar bears (Ursus maritimus). Metabolism of PCB and polybrominated biphenyl ether (PBDE) flame-retardants alter their toxicological properties and these metabolites are known to interfere with the binding of thyroid hormone (TH) to transthyretin (TTR) in rodents and humans. In polar bear plasma samples no binding of [125I]-T4 to TTR was observed after incubation and PAGE separation. Incubation of the plasma samples with [14C]-4-OH-CB107, a compound with a higher binding affinity to TTR than the endogenous ligand T4 resulted in competitive binding as proven by the appearance of a radio labeled TTR peak in the gel. Plasma incubation with T4 up to 1 mM, a concentration that is not physiologically relevant anymore did not result in any visible competition. These results give evidence that the binding sites on TTR for T4 in wild living polar bears are completely saturated. Such saturation of binding sites can explain observed lowered levels of THs and could lead to contaminant transport into the developing fetus.

(Table 3) Liver weight, blood liver parameters, and blood plasma PCB concentrations in 14 sledge dog bitches and their 14 pups in Aasiaat, west Greenland

We assessed the relationship between exposure to organohalogen polluted minke whale (Balaenoptera acutorostrata) blubber and liver morphology and function in a generational controlled study of 28 Greenland sledge dogs (Canis familiaris). The prevalence of portal fibrosis, mild bile duct hyperplasia, and vascular leukocyte infiltrations was significantly higher in the exposed group (all Chi-square: p<0.05). In case of granulomas, the frequency was significantly highest in the bitches (P generation) while the prevalence of portal fibrosis was highest in the F generation (pups) (both Chi-square: p<0.05). No significant difference between exposed and controls was found for bile acid, ALAT, and ALKP, while ASAT and LDH were significantly highest in the control group (both ANOVA: p<0.05). We therefore suggest that a daily intake of 50-200 g environmentally organohalogen polluted minke whale blubber can cause liver lesions in Greenland sledge dogs. It is reasonable to infer that other apex predators such as polar bears (Ursus maritimus) and humans may suffer from similar impacts.

Body measurements and blood plasma lipid, PCB and OH-PCB content of polar bear (U. maritimus) mothers and cubs, Svalbard

The aim of this study was to examine the plasma concentrations and prevalence of polychlorinated biphenyls (PCBs) and hydroxylated PCB-metabolites (OH-PCBs) in polar bear (Ursus maritimus) mothers (n = 26) and their 4 months old cubs-of-the-year (n = 38) from Svalbard to gain insight into the mother-cub transfer, biotransformation and to evaluate the health risk associated with the exposure to these contaminants. As samplings were performed in 1997/1998 and 2008, we further investigated the differences in levels and pattern of PCBs between the two sampling years. The plasma concentrations of Sum(21)PCBs (1997/1998: 5710 ± 3090 ng/g lipid weight [lw], 2008: 2560±1500 ng/g lw) and Sum(6)OH-PCBs (1997/1998: 228 ± 60 ng/g wet weight [ww], 2008: 80 ± 38 ng/g ww) in mothers were significantly lower in 2008 compared to in 1997/1998. In cubs, the plasma concentrations of Sum(21)PCBs (1997/1998: 14680 ± 5350 ng/g lw, 2008: 6070 ± 2590 ng/g lw) and Sum(6)OH-PCBs (1997/1998: 98 ± 23 ng/g ww, 2008: 49 ± 21 ng/g ww) were also significantly lower in 2008 than in 1997/1998. Sum(21)PCBs in cubs was 2.7 ± 0.7 times higher than in their mothers. This is due to a significant maternal transfer of these contaminants. In contrast, Sum(6)OH-PCBs in cubs were approximately 0.53 ± 0.16 times the concentration in their mothers. This indicates a lower maternal transfer of OH-PCBs compared to PCBs. The majority of the metabolite/precursor-ratios were lower in cubs compared to mothers. This may indicate that cubs have a lower endogenous capacity to biotransform PCBs to OH-PCBs than polar bear mothers. Exposure to PCBs and OH-PCBs is a potential health risk for polar bears, and the levels of PCBs and OH-PCBs in cubs from 2008 were still above levels associated with health effects in humans and wildlife.