Hepatic cytochrome P4501A and 7-ethoxyresoru®n O-deethylase induction in mullet and common sole as an indicator of toxic organic pollution in Izmir Bay, Turkey $ E. ArincË*, A. SËen Joint Graduate Program in Biochemistry, Department of Biological Sciences, Middle East Technical University, 06531 Ankara, Turkey Received 6 July 1998; received in revised form 20 February 1999; accepted 26 February 1999 Abstract In this study, the degree of induction of cytochrome P4501A-associated 7-ethoxyresoru®n O-deethylase (EROD) activity and immunochemical detection of cytochrome P4501A in leaping mullet (Liza saliens) and common sole (Solea vulgaris) were used as biomarker for assessment of polycyclic aromatic hydrocarbon (PAH) or/and polychlorinated biphenyl (PCB) type organic pollutants along the Izmir Bay on the Aegean Sea coast, Turkey. Fish were captured in May 1995 and February and June 1996. Mullet caught from Pasaport, a highly urbanized and industrial section of the Bay, had approximately 62 times more EROD activity than the feral ®sh sampled from an uncontaminated site in the Outer Bay. Mullet caught along the pollutant gradient at the three other sites in the Bay exhibited less but highly signi®cant induced EROD activity. An inverse relationship was found between the EROD activity in the ®sh and the distance between the catch point and the discharge region of polluted rivers and of industrial and domestic wastes into the Harbour. Studies using the polyclonal antibodies produced against mullet cytochrome P4501A showed a similar trend. In addition, EROD activities of benthic ®sh, common sole, captured from three dierent sites of the Bay also con®rmed and extended the results obtained with those of mullet. Except that, common sole caught from site 5, the edge of Gediz river, exhibited higher EROD activity than that of ®sh caught from site 4, Tuzla. Although, detailed qualitative and quantitative analyses of organic Marine Environmental Research 48 (1999) 147±160 www.elsevier.com/locate/marenvrev 0141-1136/99/$ - see front matter # 1999 Published by Elsevier Science Ltd. All rights reserved. PII: S0141-1136(99)00038-0 $ Preliminary results of this work have been presented in NATO-ASI on Molecular and Applied Aspects of Oxidative Drug Metabolixing Enzymes, 31 August±11 September 1997, Tekirova, Antalya, Turkey. * Corresponding author. Tel.: +90-312-210-5192; fax:+90-312-210-1289. E-mail address: earinc@metu.edu.tr (E. ArincË)