Kuiper RV †*#, Bergman Å , Vos JG *#, van den Berg M †
† Institute
for Risk Assessment Sciences, Utrecht University, The Netherlands
* Dept. of Pathobiology, Utrecht University, The Netherlands
# National Institute for Public Health and the Environment, Bilthoven (RIVM),
The Netherlands
Dept. of Environmental Chemistry, Stockholm University, Sweden.
Ethoxyresorufin-O-deethylase (EROD) activity is a popular biomarker for exposure to aryl hydrocarbon receptor (AhR) agonists. In environmental studies, complex mixtures of xenobiotics are subject to investigation where a number of pollutants inhibiting EROD activity may hamper adequate exposure assessment. This study investigates the effect of the increasingly environmentally detected polybrominated diphenylethers (PBDEs) on EROD activity in carp hepatocytes. BDEs-47, -99, -100 and 153 were selected based on their environmental abundance. Commercial penta-BDE (DE 71, Great Lakes Chemical Corp.) untreated and after clean up to remove planar impurities, a BDE-47 metabolite, 6OH-BDE-47, and PCB-153, a known inhibitor of EROD activity, were included. Freshly isolated carp hepatocytes were co-exposed for 5 days to 2,3,7,8-TCDD (0, 1, 3, 10, 30 and 100 pM), and one of the pure PBDE/PCB congeners (0, 0.25 and 2.5µM) or either DE-71 fraction (0, 0.1 and 10 µM), and EROD activity was determined. Exposure to TCDD alone resulted in dose-dependent increase of EROD activity. This induction was significantly reduced in the presence of BDEs 47, 99, 153, and both DE-71 fractions, dependent on PBDE dose, and generally not paralleled by reduced catalytic conversion of MTT as viability parameter. Particularly strong inhibition was observed for the environmentally most abundant congener BDE-47 (down to 6% of the corresponding control at 2.5µM BDE), and cleaned-up DE-71 (down to 4% of the control at 1.0 µM DE-71). BDEs-47 and 153 added shortly prior to measurement did not reduce EROD activity, indicating that inhibition is not catalytic. PCB-153 did not affect EROD activity in this study. Thus, environmentally relevant PBDEs may interfere with EROD measurement in vitro, resulting in underestimation of toxic hazard in environmental samples. Supported by FIRE, EU contract number QLK4-CT-2002-00896.
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