Apparent lack of CYP1A response to high PCB body burdens in fish from a chronically contaminated PCB site Ben F. Brammell * , David J. Price, Wesley J. Birge, Adria A. Elskus Department of Biology, University of Kentucky, Lexington, KY, USA Abstract Chronic exposure to organic contaminants such as polychlorinated biphenyls (PCBs) can lead to the development of resistance to these chemicals, a condition associated with reduced response of CYP1A1, a pollutant-inducible biomarker. We measured CYP1A activity (eth- oxyresorufin o-deethylase, EROD) and PCB concentrations in feral fish from the Town Branch/Mud River system (Logan County, KY), a stream historically contaminated with PCBs and partially remediated. As a first step in evaluating the possible development of re- sistant populations in this system, we measured CYP1A expression and PCB body burdens in resident fish from sites we previously characterized as containing biologically significant levels of CYP1A inducing compounds. Mean PCB concentrations in edible flesh ranged from 75.2 to 16.7 lg/g in fish collected from Town Branch remediated sites and were relatively low (1.23 lg/ g) in Town Branch reference site fish. However, hepatic CYP1A activity was similar among individuals of most species collected from reference and contaminated/remediated sites. The absence of elevated CYP1A levels in resident fish species despite the presence of significant PCB body burdens may indicate these fish have developed reduced sensitivity to CYP1A in- duction, a condition associated with acquired resistance to toxicants. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Resistance; Biomarker; Field collected fish; Mud river; CYP1A1 * Corresponding author: Tel.: +1-859-257-1237; fax: +1-859-257-1717. E-mail address: bfbram0@pop.uky.edu (B.F. Brammell). 0141-1136/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.marenvres.2004.03.067 www.elsevier.com/locate/marenvrev Marine Environmental Research 58 (2004) 251–255 MARINE ENVIRONMENTAL RESEARCH