Blust, R.

Celis, N.

Covaci, A.

Das, K.

Dirtu, A.

Klaren, P.H.M.

Michel, L.

Schnitzler, J.G

Thomé, J.-P.

Open Marine Archive

 - 78 -
THYROID HORMONE DISRUPTING CHEMICALS IN SEA BASS 
(DICENTRARCHUS LABRAX) FROM EUROPEAN COASTS 
Schnitzler Joseph G.1*, Loïc Michel2, Peter H.M. Klaren3, Niko Celis4, Ronny Blust4, Adrian Covaci5, Alin 
Dirtu5, Jean-Pierre Thomé6 and Krishna Das1. 
1 Laboratory of Systematics and Animal Diversity, University of Liège B6C, MARE Ctr, 4000 Liège, 
Belgium 
E-mail: joseph.schnitzler@ulg.ac.be  
2 Laboratory of Oceanology, University of Liege B6C, MARE Ctr, 4000 Liege, Belgium 
3 Department of Animal Physiology, Faculty of Sciences, Radboud University of Nijmegen, 6525 ED 
Nijmegen, the Netherlands 
4 Laboratory of Ecophysiology, Biochemistry and Toxicology, Dept of Biology,  University of 
Antwerp, 2020 Antwerp, Belgium  
5 Toxicol Center, University of Antwerp, 2610 Antwerp, Belgium  
6 Lab Ecol Anim & Ecotoxicol, Univ. Liège, 4000 Liege, Belgium  
 
Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-
Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), aldrin, dieldrin and trace elements (Cd, 
Cu, Se, Pb, Zn and Hg) were analysed in the muscle of sea bass (Dicentrarchus labrax) sampled in 
coastal regions near several important European river mouths (Gironde, Charente, Loire, Seine and 
Scheldt). These potential endocrine disrupting chemicals were present in European coastal waters. 
Even if their concentrations were well below the Maximum Residue Limits set by the governments, 
they induced alterations of the endocrine system.  
 
We established correlations between contaminant concentrations and effects on the thyroid system 
in sea bass. The contaminants induced modifications of the metabolic pathways of thyroid 
hormones and enhanced thyroid hormone synthesis. The activity of T4 Outer Ring Deiodinase was 
increased, that leads to an intensified conversion of thyroxine (T4) to its more biologically active 
form triiodothyronine (T3). Meanwhile, the activity of T4 sulfatation was reduced, that leads to a 
lowered biliary excretion of thyroid hormones. The modified metabolic pathways of the thyroid 
hormones can be interpreted as a tool to homeostatically maintain the thyroid hormone status. Of 
all tested compounds, the higher chlorinated PCBs seemed to be the most implicated in this 
perturbation. 
 
The nature of thyroid hormone synthesis, signalling and regulation is highly conserved among 
vertebrates. Although we cannot extrapolate thyroid toxicity data directly from one species to 
another, these environmental factors may well affect thyroid function in other species, including 
humans.  
 
*The first author dedicates this abstract to the freshly born Adèle and Côme. Congratulation to the 
parents! 


Thyroid hormone disrupting chemicals in sea bass (<i>Dicentrarchus labrax</i>) from European coasts

Thyroid hormone disrupting chemicals in sea bass (<i>Dicentrarchus labrax</i>) from European coasts

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