In vivo estrogenic activity of branched and linear alkylphenols in rainbowtrout (Oncorhynchus mykiss)

The in vivo estrogenic activity of the two branched alkylphenols, tert-octy lphenol and technical nonylphenol, and the two linear isoforms, n-octylphen ol and n-nonylphenol, was compared. The compounds were administered to juve nile rainbow trout (Oncorhynchus mykiss) by either intraperitoneal injectio n or water exposure and their estrogenic potential was evaluated by ELISA m easurements of induced plasma vitellogenin. Intraperitoneal injections (50 mg/kg) of the two branched alkylphenols resulted in a significant vitelloge nic response after 12 days whereas no significant induction was seen with t he two linear isomers. Water exposure for 9 days to a nominal concentration of 150 mu g/l of the alkylphenols elicited the same response pattern as se en for the injection experiment. Furthermore, in the present vitellogenin a ssay tert-octylphenol was giving a higher estrogenic response compared to t echnical nonylphenol using either of the two exposure routes. (C) 1999 Else vier Science B.V. All rights reserved.