7-ethoxyresorufin-o-deethylase (EROD) activity in rainbow trout exposed to Lambro river waters.

Relationships between cytochrome P4501A (CYP1A), natural oestrogens and xenoestrogens have been extensively investigated in vitro studies. Immature rainbow trout females (Oncorhynchus mykiss) 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 tested for the concentration of 4-nonylphenol (NP) and octylphenol (OP), known to have estrogenic effects. 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). At the end of the experimental period, ethoxyresorufin-o-deethylase (EROD), UDP-glucuronyl transferase (UDPGT) and acetylcholinesterase (AChE) enzyme activities were measured. Oestradiol (E2) plasma levels were also tested. EROD activity increased after 23-day exposure excepting to L40 fish. In these specimens lower EROD levels were observed in correspondence to the highest values of E2 confirming previous in vitro studies (Navas and Segner, Marine Environ.Res., 50: 157, 2000). UDPGT and AChE activities did not chang