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MA6 Environmental Chemistry and Toxicology of Chiral Pollutants
() Toxicokinetics of Chiral Polychlorinated Biphenyls Present in Technical Mixtures in Rainbow Trout (Oncorhynchus Mykiss).
Buckman, A1, 2, Chow, E3, Brown, S2, Solomon, K1, Fisk, A4, Wong, C3, 1 University of Guelph, Guelph, Ontario, Canada2 Environment Canada, Burlington, Ontario, Canada3 University of Alberta, Edmonton, Alberta, Canada4 University of Georgia, Athens, Georgia, USA
ABSTRACT- The composition of chiral polychlorinated biphenyls (PCBs) was determined in rainbow trout exposed to Aroclor mixtures, to determine if these fish are stereoselectively eliminating these congeners during dietary accumulation of PCBs. Previous bioaccumulation and depuration experiments based on achiral analysis have found little evidence for PCB biotransformation. However, recent reports of enantioselective elimination of PCBs by fish fed individual congeners suggested that they may slowly biotransform labile congeners in PCB mixtures. Juvenile rainbow trout held at 8°C and 12°C were exposed to environmentally relevant dietary concentrations of three Aroclor mixtures (1248, 1254, 1260) in food for 30 d followed by an additional 160 d of non-spiked food to further assess the ability of rainbow trout to biodegrade PCB congeners and produce hydroxylated PCB (OH-PCB) metabolites. Half-lives of PCB congeners ranged from 58 to 200 d and 38 d to 89 d for the 8°C and 12°C treatments, respectively, assimilation efficiencies ranged from 50 to 70%, and biomagnification factors (BMFs) ranged from 2.9 to 6.9 at both temperatures. There was no evidence of any significant biotransformation of any PCB congeners in 8°C treatments based on achiral measures such as half-lives (t1/2), BMFs, and lack of detection of OH-PCBs in blood plasma. However, (+)-PCB 136 was depleted relative to its antipode, suggesting stereoselective elimination of this congener consistent with previous work. Treatments at 12°C showed presence of OH-PCBs in the plasma at d 30 of uptake, and systemic deviation of congeners amenable to cytochrome P-450 2B attack from the t1/2-Kow relationship, suggesting in vivo biotransformation consistent with enantiomer compositions of chiral PCBs. Our results suggest that chiral analysis can be a useful tool in detecting and elucidating factors affecting bioaccumulation of persistent pollutants in biota.
Key words: biotransformation, chiral PCBs, temperature, OH-PCBs
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