Inaugural Conference - June 2002

G.C.M. Grinwis¹, J.G. Vos^1,2, A.D. Vethaak³ and P.W. Wester²

1. Department of Pathology, Faculty of Veterinary Medicine, Utrecht University, The Netherlands
2. National Institute of Public Health and the Environment, The Netherlands
3. National Institute for Coastal and Marine Management, The Netherlands

Field and semi-field (mesocosm) studies with European flounder (Platichthys flesus) have shown an increased prevalence of (pre)neoplastic liver lesions and lymphocystis disease (a viral infection) in correlation with environmental pollution. However, it was not possible to establish a causal relationship between specific chemical pollutants and diseases under field- and semi-field conditions.
Therefore we examined the effects of some potentially causative agents like bis(tri-n-butyltin)oxide (TBTO), 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), and 3,3’,4,4’,5 pentachlorobiphenyl (PCB-126) in flounder in a controlled laboratory setting. The effects were evaluated using general toxicological parameters, histopathology and immunological function tests.
Short-term aqueous exposure of flounder to TBTO, in concentrations that were in the same order of magnitude as higher TBT field-levels, caused mortality after 7-12 days and gill lesions. Also, exposure related reduction of the non-specific resistance and a decrease of the relative thymus volume were noted.
Oral exposure of flounder to high levels of TCDD and PCB-126 resulted in a strong and significant induction of cytochrome P450 in several cell types (e.g. hepatocytes, endothelial cells and hematopoietic cells). PCB-126 induced a significant reduction of the relative thymus volume but TCDD did not.
The implications of the effects on the immune system have to be addressed in infection experiments but a possible role for TBTO and PCB-126 in the increased prevalence of some diseases in flounder is not unlikely.

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