Comparative hepatic activity of xenobiotic‐metabolizing enzymes and concentrations of organohalogens and their hydroxylated analogues in captive greenland sledge dogs ( Canis familiaris)

• Published in: Environmental Toxicology and Chemistry
• Main Authors: Verreault, Jonathan, Maisonneuve, France, Dietz, Rune, Sonne, Christian, Letcher, Robert J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Greenland; Balaenoptera acutorostrata; minke whale
• Online Access: http://dx.doi.org/10.1897/08-176.1; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1897%2F08-176.1; https://setac.onlinelibrary.wiley.com/doi/pdf/10.1897/08-176.1

Abstract A captive study was performed with Greenland sledge dogs ( Canis familiaris ) fed a naturally organohalogen‐contaminated diet (Greenland minke whale [ Balaenoptera acutorostrata ] blubber; exposed group) or a control diet (pork fat; control group). The catalytic activity of major xenobiotic‐metabolizing phase I and II hepatic microsomal enzymes was assessed. Relative to control dogs, ethoxyresorufin‐ O ‐deethylase (EROD) activity in exposed dogs was twofold higher ( p = 0.001). Testosterone hydroxylation yielded 6β‐ and 16β‐hydroxy (OH) testosterone and androstenedione, with higher rates of production (23–27%; p ≤ 0.03) in the exposed individuals. In the exposed dogs, epoxide hydrolase (EH) activity was 31% higher ( p = 0.02) relative to the control dogs, whereas uridine diphosphoglucuronosyl transferase (UDPGT) activity was not different ( p = 0.62). When the exposed and control dogs were combined, the summed (Σ) plasma concentrations of OH‐polychlorinated biphenyl (PCB) congeners were predicted by plasma ΣPCB concentrations and EROD activity ( p ≤ 0.04), whereas testosterone hydroxylase, EH, and UDPGT activities were not significant predictors of these concentrations. Consistent results were found for individual OH‐PCB congeners and their theoretical precursor PCBs (e.g., 4‐OH‐CB‐187 and CB‐183, and 4‐OH‐CB‐146 and CB‐146) and for EROD activity. No association was found between ΣOH–polybrominated diphenyl ether (PBDE) and ΣPBDE plasma concentrations, or between potential precursor‐metabolite pairs, and the enzyme activities. The present results suggest that liver microsomal EROD activity and plasma PCB concentrations have a greater (e.g., relative to EH activity) predictive power for the occurrence of plasma OH‐PCB residues in sledge dogs. These results also suggest that plasma OH‐PBDEs likely are not products of cytochrome P450‐mediated transformation but, rather, are accumulated via the diet.