Regular ArticleImmunoquantitation and Microsomal Monooxygenase Activities of Hepatic Cytochromes P4501A and P4502B and Chlorinated Hydrocarbon Contaminant Levels in Polar Bear (Ursus maritimus)
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Simulating changes in polar bear subpopulation growth rate due to legacy persistent organic pollutants – Temporal and spatial trends
2021, Science of the Total EnvironmentConcentrations and profiles of organochlorine contaminants in North Pacific resident and transient killer whale (Orcinus orca) populations
2020, Science of the Total EnvironmentCitation Excerpt :Organochlorines (OCs), such as DDTs and polychlorinated biphenyls (PCBs), are persistent, widespread environmental contaminants that are resistant to metabolism and have been shown to bioaccumulate through marine food webs (Fisk et al., 2001; Ruus et al., 2002; Hoekstra et al., 2003). However, some large marine mammal species, notably polar bears (Ursus maritimus), have an excellent ability to metabolize some OCs (Muir et al., 1988; Letcher et al., 1996, 1998). Accordingly, OCs have been used as intrinsic chemical tracers to infer sources of OCs, foraging areas, and migration patterns of many marine species (Ramos and González-Solís, 2012), including Pacific herring (West et al., 2008), Atlantic salmon (Salmo salar) (Svendsen et al., 2008, 2009), bluefish (Pomatomus saltatrix) (Deshpande et al., 2016a), bluefin tuna (Thunnus thynnus) (Deshpande et al., 2016b), Greenland sharks (Somniosus microcephalus) (Fisk et al., 2002), bottlenose dolphins (Tursiops truncatus) (Borrell et al., 2006; Fair et al., 2010), humpback whales (Megaptera novaeangliae) (Elfes et al., 2010), and killer whales (Herman et al., 2005; Krahn et al., 2007a).
Hepatic phase I and II biotransformation responses and contaminant exposure in long-finned pilot whales from the Northeastern Atlantic
2018, Marine Environmental ResearchCitation Excerpt :For example, BROD and PROD have not been useful markers of CYP2B induction in hamster (Mesocricetus auratus) and cynomologus monkey (Macaca fascicularis) (Weaver et al., 1994). The use of PROD as a biomarker of CYP2B induction in marine wildlife has been called into question as PROD has been found to be highly correlated to CYP1A protein content (Letcher et al., 1996) and EROD activity, suggesting that CYP1A is a single and common catalyst of these substrates (Ruus et al., 2002). In seals, it has been proposed that CYP2B enzymes may be structurally different and have different substrate specificities than in rodent and humans, and may not be a good biomarker for contaminants that induce CYP2B (Nyman et al., 2001).
Ecotoxicologic Stress in Arctic Marine Mammals, With Particular Focus on Polar Bears
2018, Marine Mammal Ecotoxicology: Impacts of Multiple Stressors on Population HealthSea ice-associated decline in body condition leads to increased concentrations of lipophilic pollutants in polar bears (Ursus maritimus) from Svalbard, Norway
2017, Science of the Total EnvironmentCitation Excerpt :We expected that mobilization of lipophilic PCBs from adipose tissue in bears with poor body condition would lead to the induction of biotransformation systems and formation of OH-PCBs, yet this is not what we observed. The activity of enzymes involved in biotransformation of PCBs in polar bears (cytochromes P450 isozymes CYP1A, CYP2B and CYP3A, Bandiera et al., 1995; Letcher et al., 1996) may also be regulated by nutritional status. For example, in an experimental study on arctic foxes CYP2B and CYP3A activities measured as 6β and 2β-hydroxylation of testosterone were higher in fat compared to lean foxes irrespective of contaminant exposure (Helgason et al., 2013).
Evaluation of hepatic biotransformation of polybrominated diphenyl ethers in the polar bear (Ursus maritimus)
2016, ChemosphereCitation Excerpt :Whether the rates would be greater if freshly-prepared polar bear liver microsomes were used is unknown. The total CYP content of the polar bear liver microsomes used for the present study was previously shown to be similar to the total CYP content typically measured in rat liver microsomes (Bandiera et al., 1995; Letcher et al., 1996). Moreover, CYP-mediated activities, including alkoxyresorufin O-dealkylase and testosterone hydroxylase, were easily measurable in the polar bear liver microsomes (Bandiera et al., 1995; Letcher et al., 1996), indicating that the hepatic preparations were catalytically active.