Organochlorine compounds in liver and concentrations of vitellogenin and 17beta-estradiol in plasma of sea bass fed with a commercial or with a natural diet.

Results from previous experiments directed to determine the effect of different nutritional factors or the effect of xenobiotics on hormonal control of reproduction, lead to the hypothesis that hormonal perturbations repeatedly observed in sea bass (Dicentrarchus labrax) broodstock feeding commercial diets could have been caused by the presence of aryl hydrocarbon receptor (AhR) ligands, such as dioxins, furans and polychlorinated biphenyls (PCBs) in the diet. To evaluate this hypothesis, dioxins and related compounds were analysed in liver of female sea bass fed with a commercial or with a natural diet consisting of trash fish (bogue, Boops boops), and concentrations of vitellogenin (VTG) and 17beta-estradiol (E2) were determined in plasma obtained previously in monthly samplings of these animals. As observed in other experiments, females fed with a commercial diet exhibited lower VTG and higher E2 plasma levels than females fed with the natural diet. In liver, sea bass fed with the commercial diet exhibited a profile clearly dominated by high-chlorinated dioxins while in fish fed with the natural diet this profile was dominated by low chlorinated furans. However, typical AhR ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin showed no differences between groups or, as is the case of planar PCBs, showed higher concentrations in the liver of fish fed with the natural diet. These results do not permit to explain the observed hormonal alterations by a possible antiestrogenic effect caused by dioxins and related compounds.