Sex steroid and vitellogenin plasma levels in intersexual fish captured in a polluted area of the Po river.

Immature rainbow trout females (Oncorhynchus mykiss, n=250) were exposed for 10 and 23 days to waters collected from the River Lambro, which drains areas characterized by severe anthropic pressure. Water was collected every two days and analysed for wide-spread xenoestrogens such as 4-nonylphenol (NP) and octylphenol (OP). Fish were exposed to graded concentrations of Lambro water in a flow-through system. Five aquaria, respectively containing tap unchlorinated water (negative control), 10%, 20% and 40% Lambro and 20% sewage effluent (positive control) were set up (C, L10, L20, L40 and EF20, respectively). Plasma levels of vitellogenin (Vtg), 17ß-oestradiol (E2) and testosterone (T) were measured. Histomorphological aspects of gonads and liver were also evaluated. Significant increase of plasma steroid and Vtg levels were observed in L40 fish after 10-day exposure. E2 significantly increased after 23-day exposure, in a dose-dependent manner. E2 and Vtg levels were never correlated in any of the treated fish. After 23-day exposure, a marked decrease of T levels in L40 and EF20 was observed.