In vivo biomarkers of estrogenicity: limitation of interpretation in wild environment.

In the literature, multiple sample schemes have been developed to assess the environmental impacts of endocrine-disruptor compounds (EDCs) from sewage treatment plant (STPs). In the present work, the plan study was designed by sampling upstream and downstream wild populations of gudgeons from two STP stations (La Roche and Rochefort, Belgium). Biomarkers of feminization were assayed, such as vitellogenin expression and ovotestis screening. Parameters involved in steroidogenesis (sex steroids and brain aromatase activity) were also investigated to better characterize interactions between living organisms coping with a complex mixture of compounds loaded by treated effluent. Results displayed moderate differences between upstream and downstream populations of wild gudgeons. Moreover, accounted differences have demonstrated the difficulty of characterizing the mixture of compounds to which fish are exposed in the aquatic milieu. Actually, physiological responses were not representative of a particular group of EDC (e.g., estrogenlike compounds) but instead confirm an association between different categories of compounds. Even if powerful biomarkers of estrogenicty were developed, the interpretation of the response profile remains limited through in vivo parameters due to the complex association between compounds of various origins.