title: Biotransformation and bioconcentration of pyrene in Daphnia magna.
abstract: Water fleas (Daphnia magna) were exposed to [14C]pyrene in the presence and absence of piperonyl butoxide (PBO), a general cytochrome P450 (CYP) inhibitor, in organic carbon-free artificial freshwater (AFW, DOC<0.2 mg l(-1)) and in natural lake water (DOC=19.9 mg l(-1)) for 24 h. The bioconcentration of total radioactivity after 24 h exposure was 50% lower in the natural lake water, indicating decreased bioavailability of pyrene by the dissolved organic matter. However, the proportions of parent compound were only ca. 12 and 19% of the total body burden in daphnids exposed in AFW and natural lake water, respectively. Therefore, the tissue concentration of the parent pyrene was not significantly different in the daphnids exposed in the two different waters. Due to extensive biotransformation the bioconcentration factor (BCF) of parent pyrene was only 16 and 23% of the BCF calculated on the basis of total radioactivity in the daphnids in AFW and natural lake water, respectively. The proportion of parent pyrene was significantly higher (over 60%) in the daphnids exposed simultaneously to PBO, which indicates the involvement of CYP monooxygenases in the biotransformation. Furthermore, increasing PBO concentration decreased the accumulation of total radioactivity in AFW but not in the natural lake water. The data demonstrate capability and importance of CYP monooxygenases in biotransformation of polycyclic aromatic hydrocarbons in D. magna.
authors.affiliation: Department of Biology, Laboratory of Aquatic Ecology and Ecotoxicology, University of Joensuu, P.O. Box 111, FIN-80101, Joensuu, Finland. jarkko.akkanen@joensuu.fi
authors.forename: Jarkko
authors.initials: J
authors.lastname: Akkanen
authors.forename: Jussi V K
authors.initials: JV
authors.lastname: Kukkonen
mesh_terms: D000818:Animals; D001682:Biological Availability; D001711:Biotransformation / Q000502:physiology; D002250:Carbon Radioisotopes; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003621:Daphnia / Q000201:enzymology / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics; D005618:Fresh Water / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry; D010574:Pesticide Synergists / Q000493:pharmacokinetics; D010882:Piperonyl Butoxide / Q000493:pharmacokinetics; D011721:Pyrenes / Q000493:pharmacokinetics*; D011849:Radioactive Tracers; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics
chemical_list: D002250:Carbon Radioisotopes; D004791:Enzyme Inhibitors; D009930:Organic Chemicals; D010574:Pesticide Synergists; D011721:Pyrenes; D011849:Radioactive Tracers; D014874:Water Pollutants, Chemical; D003577:Cytochrome P-450 Enzyme System; D010882:Piperonyl Butoxide