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Title: Cytochrome P450 Induction and Gene Expression in Channel Catfish (Ictalurus punctatus) Following Wastewater Treatment Plant Effluent Exposure in Field and Laboratory Settings

item WHATLEY, ALICIA - Troy University
item CHO, IN - Troy University
item MAGRATH, CHRISTI - Troy University
item STEWART, PAUL - Troy University
item Li, Robert

Submitted to: Journal of Environmental Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2010
Publication Date: 10/16/2010
Citation: Whatley, A., Cho, I.K., Magrath, C., Stewart, P.M., Li, R.W. 2010. Cytochrome P450 Induction and Gene Expression in Channel Catfish (Ictalurus punctatus) Following Wastewater Treatment Plant Effluent Exposure in Field and Laboratory Settings. Journal of Environmental Protection. 1:362-373.

Interpretive Summary: Molecular biomarkers are useful tools for determining the impact of water-bourne contaminants on living organisms in the aquatic environment. Channel catfish has a very wide natural distribution in the North America. They thrive in many water habitats of rivers, reservoirs, ponds, and lakes, preferring clear and slow-moving water. As a highly mobile species, channel catfish is susceptible to contaminants in the aquatic environment. Given the importance of catfish as a protein source for humans, pollutant intake by catfish has both a direct and indirect effect on human health. The ubiquitous distribution and unique habitats of catfish make it an excellent candidate to be exploited for water quality assessment. One important and useful molecular biomarker is induction of the cytochrome P450 enzyme, measured as ethoxyresorufin-O-deethylase (EROD) activity, which is involved in metabolism of a variety of drugs and xenobiotics. Our Results suggested monitoring hepatic cytochrome p450 induction and EROD activity in channel catfish provides a means to assess the environmental impact of water pollution.

Technical Abstract: The objectives of this study were as follows: (1) to establish a baseline ethoxyresorufin-O-deethylase (EROD) activity level in channel catfish (Ictalurus punctatus), (2) to assess changes in induction of cytochrome P450 enzyme in channel catfish following exposure to creek water at the discharge point from the Troy (Alabama) Wastewater Treatment Plant (TWWTP) compared to upstream samples from Walnut Creek, (3) to compare EROD activity in populations maintained in laboratory and field settings, and (4) to quantify cytochrome P450 (CYP1A) gene expression. Enzyme activity was measured fluorometrically and CYP1A gene expression was analyzed by quantitative real-time reverse transcription polymerase chain reaction. A mean EROD baseline was established at 0.03 nmol/min/µg of protein. The overall mean field effluent (TF) EROD had a significant 5-fold increase over field upstream (UF) exposed catfish; and overall mean laboratory effluent (TL) exposed catfish EROD had a significant 1.8-fold increase over laboratory upstream (UL) exposed catfish. Field exposures generally showed more robust enzyme induction over laboratory exposures on all sampling days. Expression of the CYP1A gene following TF exposure was 6-fold over UF. Results suggested that in situ exposure to wastewater pollutants using caged test organisms provided a much more sensitive local monitor of pollutant exposure and biological impact than ex situ toxicological studies.