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Relation among cytochrome p450, ah-active pcb congeners and dioxin equivalents in pipping black-crowned night-heron embryos

Authors

  • Barnett A. Rattner,

    Corresponding author
    1. National Biological Survey, Patuxent Environmental Science Center, 12011 Beech Forest Road, Laurel, Maryland 20708
    • National Biological Survey, Patuxent Environmental Science Center, 12011 Beech Forest Road, Laurel, Maryland 20708
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  • Jeff S. Hatfield,

    1. National Biological Survey, Patuxent Environmental Science Center, 12011 Beech Forest Road, Laurel, Maryland 20708
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  • Mark J. Melancon,

    1. National Biological Survey, Patuxent Environmental Science Center, 12011 Beech Forest Road, Laurel, Maryland 20708
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  • Thomas W. Custer,

    1. National Biological Survey, Patuxent Environmental Science Center, 12011 Beech Forest Road, Laurel, Maryland 20708
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  • Donald E. Tillitt

    1. National Biological Survey, Midwest Science Center, 4200 New Haven Road, Columbia, Missouri 65201
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Abstract

Pipping black-crowned night-heron (Nycticorax nycticorax) embryos were collected from a relatively uncontaminated site (next to Chincoteague National Wildlife Refuge, VA) and three polluted sites (Cat Island, Green Bay, Lake Michigan, WI; Bair Island, San Francisco Bay, CA; West Marin Island, San Francisco Bay, CA). Hepatic cytochrome P450-associated monooxygenases and cytochrome P450 proteins, induced up to 85-fold relative to the reference site, were associated with concentrations of total polychlonrinated biphenyls (PCBs) and 11 PCB congeners that are presumed to express toxicity through the arylhydrocarbon (Ah) receptor Multiple regression revealed that up to 86% of the variation of cytochrome P450 measurements was accounted for by variation in the concentration of these PCB congeners. Toxic equivalents (TEQs) of sample extracts, predicted mathematically (summed product of PCB congener concentrations and toxic equivalency factors), and dioxin equivalents (TCDD-EQs), derived by bioassay (ethoxyresorufin-O-dealkylase activity of treated H4IIE rat hepatoma cells), were greatest in Cat Island samples. Cytochrome P450-associated monooxygenases and cytochrome P450 proteins were related to TEQs and TCDD-EQs; adjusted r2 often exceeded 0 5 for the relation among mathematically predicted TEQs and cytochrome P450 measurements. These data extend previous observations in heron embryos of an association between P450 and total PCB burdens to include Ah-active PCB congeners, and presumably other compounds, which interact similarly with the Ah receptor Benzyloxyresorufin O-dealkylase, ethoxyresorufin O-dealkylase, and cytochrome P450 1A appear to be the most reliable measures of exposure to Ah-active PCB congeners in black-crowned night-heron embryos. These findings provide further evidence that cytochrome P450-associated parameters have considerable value as a biomarker for assessing environmental contamination of wetlands

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