Bioavailability of PAHs in the Biobio river (Chile): MFO activity and biliary fluorescence in juvenile Oncorhynchus mykiss

Cytochrome P450-dependent monooxygenase (MFO) activity and levels of bile P AH metabolites were measured in fish (Oncorhynchus mykiss) exposed to Biobi o river (Chile) water. Experiments were performed simultaneously in both th e field and laboratory to investigate whether the river water contained not able bioavailable PAH fractions. The field experiment was conducted using f ish caged for 41 days at La Mochita (Biobio river mouth) whereas the labora tory experiment involved a 21-day exposure treatment with water collected i n the same area. Induction of hepatic MFO, assayed by benzo(a)pyrene monoox ygenase activity (BaPMO), and levels of PAH metabolites in the bile were me asured in groups of eight (field experiment) and four specimens (laboratory experiment) sampled after 5, 10, 21 and 41 days of exposure. BaPMO was ind uced by a factor of 23 and 25 in fish caged for 21 and 41 days, respectivel y. Likewise, a significant BaPMO induction was found in the fish group expe rimentally exposed to river water for 21 days. Biliary fluorescence measure ments, recorded by fixed wavelength fluorescence (FF) and synchronous fluor escence spectroscopy (SFS), revealed significantly high levels of PAH metab olites in bile samples of fish caged for 21 and 41 days. A positive relatio nship was found between BaPMO activity and biliary PAH metabolites. This st udy provides evidences that (i) Biobio river water contains a significant b ioavailable PAH fraction in terms of marked effects on fish and (ii) the bi ological indicators MFO activity and bile PAH metabolites represent an exce llent screening methodology to assess PAH exposure. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.