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(PM239) The role of phase II enzymes in the biotransformation of benzo[a]pyrene in Fundulus heteroclitus.
Gaworecki, K1, van den Hurk, P1, 1 Clemson University, Pendleton, SC, USA
ABSTRACT- The role of biotransformation enzymes in aquatic species is an important factor in the elimination of, and sensitivity to, xenobiotics. In short term exposure scenarios, sulfotransferase (SULT) and glucuronosyltransferase (UGT) play major roles in detoxification as competitive pathways of biotransformation. In mammalian systems, sulfotransferase generally has a higher affinity and a lower capacity for conjugating substrates. UGT acts as a backup system with a lower affinity but a higher capacity for the xenobiotics. Previously, we have shown that F. heteroclitus (mummichog) possess minimal levels of sulfotransferase activity. In order to determine the roles of SULT and UGT in biotransformation, male mummichogs were dosed with a single i.p. injection containing the vehicle control, 10 mg/kg benzo[a]pyrene (BaP), 5 mg/kg pentachlorophenol (PCP, a known SULT inhibitor), or a mixture of BaP + PCP. At 12, 24, 48, and 72 hours post injection, two fish were pooled from each of the four replicate tanks per treatment. Livers were extracted and analyzed for EROD, UGT, and SULT activities. Gall bladders were extracted to measure overall BaP metabolite fluorescence in the bile. Glucuronide and sulfate conjugates were quantified by HPLC. SULT activity was only inhibited at 12 hours by the PCP treatment. There were no differences in overall bile fluorescence between treatments of BaP and BaP + PCP. The treatment of BaP + PCP appeared to have more UGT conjugates as well as UGT activity at 48 hours compared to BaP alone, however, these differences were not significant. There were no quantitative differences in sulfate conjugates between BaP and BaP + PCP treatments, however, they made up less than 1% of total biliary conjugates. These results support the lack of SULT activity in mummichog, although possible excretion of sulfated conjugates through urine was not measured.
Key words: benzo[a]pyrene, Fundulus heteroclitus, phase II enzymes
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