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() Biological response in PCB exposed sea stars.

Danis, B1, Warnau, M2, 1 Université Libre de Bruxelles, Brussels, Belgium2 International Atomic Energy Agency, Monaco, Principauté de Monaco

ABSTRACT- PCBs are among the most problematic contaminants in the marine environment: they are resistant, readily bioaccumulated and some are highly toxic. Recognized as a good bioindicator species, the common NE Atlantic sea star Asterias rubens (L.) was chosen as an experimental model to study PCB bioaccumulation following exposure through different routes and subsequent biological responses, at immune and sucellular levels. The considered responses were (i) the production of reactive oxygen species (ROS) by sea stars amoebocytes and (ii) the induction of a cytochrome P450 immunopositive protein (CYP1A IPP). Experimental exposures carried out have shown that A. rubens efficiently accumulates PCBs at exposure concentrations matching those encountered in the field. Uptake kinetics were related to the planar conformation of the congener: non-coplanar PCB uptake was described using saturation models, whereas coplanar PCBs (c-PCBs) bioaccumulated according to bell-shaped kinetics. Seawater was by far the most efficient route for PCB uptake in sea stars : even if PCB levels in seawater are extremely low compared to sediment-associated concentrations, seawater constitutes a non-negligible route for PCB uptake. Among the different body compartments, bodywall displayed the highest bioaccumulative potency and can therefore be considered as particularly interesting for field biomonitoring applications. PCBs were found to significantly alter ROS production, in a congener-specific way : c-PCBs were found to affect, and probably impair sea stars immune system, whereas non-coplanar congeners had no effect. Modulation of ROS production in our experimental conditions were found to potentially lead to altered immunity, and in extenso to impair sea stars defence against pathogenic agents. Experimental work has shown that the induction of CYP1A IPP was also related to PCB exposure in a congener-specific fashion: c-PCBs alone were found to strongly induce the production of CYP1A IPP according to a dose-dependent relationship. Results obtained have highlighted many similarities between the dioxin-like responsiveness of CYP1A IPP induction in sea stars and that occurring in vertebrates. In our experiments PCB toxicity was almost always attributable to the sole c-PCBs, which strongly suggests that the selection of congeners to be considered in monitoring programmes should include coplanar PCBs.

Key words: PCB, Sea stars, CYP1A, Immunotoxicity

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