EROD and CYP1A protein in channel catfish (Ictalurus punctatus) from an urban estuary relative to that in benzo[a]pyrene-exposed hatchery specimens

Bottom-feeding fish such as flounder and killifish have been widely used in monitoring hepatic monooxygenase induction in polluted water bodies. While channel catfish are often utilized in tissue monitoring of fresh and estuarine water bodies, few data are available on their use in environmental monitoring of hepatic monooxygenase activity. In this project, the presence of CYP1A protein was verified in channel catfish through recognition by Mab 1-12-3, an antibody which recognizes the CYP1A homologue in a variety of teleost species. CYP1A protein levels and 7-ethoxyresorufin-o-deethylase (EROD) activity in laboratory control and benzo-a-pyrene (BaP)-challenged channel catfish were compared to those in feral channel catfish from Back River, an urban estuarine tributary to Chesapeake Bay. Though more variable, mean CYP1A protein levels in the field-collected fish were similar to those of the BaP-induced laboratory fish. However, EROD activity of the Back River fish was less than one half that observed in the BaP-induced laboratory fish. When normalized to CYP1A protein levels, EROD activity was slightly lower in the Back River fish than either the laboratory control or BaP-treated fish. This finding may indicate possible inhibition or inactivation of the CYP1A protein in the feral fish.