Rattner, B. A., Hatfield, J. S., Melancon, M. J., Custer, T. W., and Tillitt, D. E.,
1994, Relation among cytochrome P450, Ah-active PCB congeners and dioxin
equivalents in pipping black- crowned night-heron embryos: Environmental
Toxicology and Chemistry, v. 13, no. 11, p. 1805-1812.

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 polychlorinated 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 r super(2) 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.

Keywords

water-pollution-effects, polychlorinated-biphenyls, biomonitoring-, toxicity-,
birds-, enzymes-, aquatic- environment, USA-, Ah-receptors,
arylhydrocarbon-receptors, PCB-, TCDD-, Nycticorax-nycticorax, water- pollution,
PCB-compounds, pollution-effects, aquatic-birds, toxicology-, enzymatic-activity,
ANW,-USA, USA,- Michigan, INE,-USA,-California, dioxin-