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Hydrocarbon-inducible cytochrome P4501A (CYP1A) expression was measured, as ethoxyresorufin-O-deethylase (EROD) activity, in livers of wintering harlequin ducks (Histrionicus histrionicus) captured in areas of Prince William Sound, Alaska, USA, oiled by the 1989 Exxon Valdez spill and in birds from nearby unoiled areas, during 2005 to 2009 (up to 20 years following the spill). The present work repeated studies conducted in 1998 that demonstrated that in harlequin ducks using areas that received Exxon Valdez oil, EROD activity was elevated nearly a decade after the spill. The present findings strongly supported the conclusion that average levels of hepatic EROD activity were higher in ducks from oiled areas than those from unoiled areas during 2005 to 2009. This result was consistent across four sampling periods; furthermore, results generated from two independent laboratories using paired liver samples from one of the sampling periods were similar. The EROD activity did not vary in relation to age, sex, or body mass of individuals, nor did it vary strongly by season in birds collected early and late in the winter of 2006 to 2007, indicating that these factors did not confound inferences about observed differences between oiled and unoiled areas. We interpret these results to indicate that harlequin ducks continued to be exposed to residual Exxon Valdez oil up to 20 years after the original spill. This adds to a growing body of literature suggesting that oil spills have the potential to affect wildlife for much longer time frames than previously assumed. Environ. Toxicol. Chem. 2010;29:1138–1145. © 2010 SETAC [ABSTRACT FROM AUTHOR]

Six-month-old lesser scaup (Aythya affinis) and nestling tree swallows (Tachycineta bicolor) were injected intraperitoneally with β-naphthoflavone (BNF) in corn oil or in vehicle alone. Liver samples were taken and stored at -80°C until microsome preparation and monooxygenase assay. Skin samples were placed in buffered formalin for subsequent immunohistochemical (IHC) analysis for cytochrome P4501A (CYP1A). Lesser scaup treated with BNF at 20 or 100 mg/kg body weight showed approximately 6- to 18-fold increases in four monooxygenases (benzyloxyresorufin-O-dealkylase, ethoxyresorufin-O-dealkylase, methoxyresorufin-O-dealkylase, and pentoxyresorufin-O-dealkylase). No IHC response was observed for CYP1A in the skin of vehicle-injected ducks, whereas in the skin from BNF-treated ducks, the positive IHC response was of similar magnitude for both dose levels of BNF. Tree swallows injected with BNF at 100 mg/kg, but not at 20 mg/kg, showed significant increases (approximately fivefold) in hepatic microsomal O-dealkylase activities. Cytochrome P4501A was undetectable by IHC response in skin from corn oil-treated swallows, but positive IHC responses were observed in the skin of one of five swallows at 20 mg/kg and four of five swallows at 100 mg/kg. Although these data do not allow construction of significant dose-response curves, the IHC responses for CYP1A in skin support the possible use of this nonlethal approach for biomonitoring contaminant exposure of birds. In addition, the CYP1A signal observed at the bases of emerging feathers suggest that these might provide less invasive sampling sites for IHC analysis of CYP1A. [ABSTRACT FROM AUTHOR]

Yellow perch were given a single intraperitoneal injection of polychlorinated biphenyl (PCB) 126 dissolved in corn oil at nominal concentrations of 0, 10, 100, and 500 µ g/kg body weight. Following the injection, the fish were held for four weeks under photothermal conditions characteristic for Ohio, USA, and fed a commercial fish food. Thereafter, they were sacrificed to examine the PCB 126 concentrations in the liver and to assess the contaminant effects on hepatic P4501A activity, reproductive hormones in plasma, and steroidogenic potential of gonads. The administered doses resulted in liver concentrations of 0.8 (corn oil control), 12.1, 38.9, and 174.5 µ g/kg wet tissue weight. Hepatic P4501A indices were differentially affected depending on both the PCB 126 dose and fish gender. In untreated fish, the P4501A protein and ethoxyresorufin-O-deethylase activity were several times lower in females than in males. In treated males, the hepatic P4501A was inhibited by all three PCB 126 doses. In females, a significant P4501A induction occurred in those dosed with 10 µ g/kg, while no changes were found in the two higher-dosed female groups in comparison to controls. A significant negative correlation was observed between hepatic P4501A indices and gonad somatic indexes values and plasma estradiol concentrations. The PCB 126 administration produced alterations in concentrations of plasma sex hormones in females but not in males. The in vitro steroidogenic potential of the female and male gonads was not affected by the in vivo PCB 126 treatment. [ABSTRACT FROM AUTHOR]

Monoclonal antibody 1-12-3 (MAb 1-12-3) recognizes an epitope exclusive to cytochrome P450s in subfamily 1A (CYP1A) from all vertebrates tested so far, including one amphibian species. In this study, we first tested the utility of MAb 1-12-3 for detection of presumed CYP1A proteins in hepatic microsomes of northern leopard frogs treated without or with 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Statistical analysis showed that ethoxyresorufin-O-deethylase (EROD) activities and CYP1A equivalents in treated groups were significantly increased at doses =/>2.3 mg/kg compared with the control groups (p < 0.05), and the increases were maintained for at least four weeks. This result confirmed that MAb 1-12-3 can be used for detection of CYP1A in northern leopard frogs and indicated that CYP1A is the primary catalyst for EROD in this species. In a subsequent experiment, sections of organs ofPCB 126-treated frogs were immunohistochemically stained with MAb 1-12-3 to identify localization of the CYP1A in different cell types. The CYP1A staining was seen prominently in hepatocytes and epithelium of nephronic duct, while capillaries close to gastric epithelium and submucosal vascular epithelium in both stomach and intestine exhibited moderate to strong staining. The CYP1A was immunodetected in coronary endothelium and the vascular endothelium of lung and gonad. In skin, mild staining was seen in epithelial cells of mucous glands and serous glands and in vascular endothelium, demonstrating induction of CYP1A in the dermal layer. [ABSTRACT FROM AUTHOR]