Sex steroid and vitellogenin levels, gonad and liver morphology in rainbow trout exposed to natural mixture of pollutants.

Chemical analyses of bed sediments and tissues of wild cyprinids sampled downstream from the confluence of the River Lambro, a polluted tributary that drains a heavily industrialised sub-basin of the Po River, showed the presence of moderate concentrations of xenoestrogens (Viganò et al., Arch. Environ. Contam. Toxycol., 38: 209, 2000). About 50% of adult specimens, sampled in the same area in the period 1999-2001, showed intersexual gonads (Viganò et al., Sci. Tot. Environ., 269: 189, 2001). Aim of this study was to investigate the presence of altered sex steroid and vitellogenin (Vtg) pattern in these specimens. Intersex were classified as F1*, in which female gametes were represented by previtellogenic oocytes and F3* in which female gametes were represented by vitellogenic atretic oocytes. 17-oestradiol (E2), testosterone (T) and Vtg concentrations were measured by means of RIA and ELISA, respectively. Results were compared to data obtained in specimens collected in a not polluted area upstream the confluence of the Lambro River. Significantly lower values of T were measured in F1* (if compared to "normal" immature females) and significantly lower values of both E2 and T were measured in F3* (if compared to "normal" vitellogenic females). The last showed a significant decrease of Vtg too.