Bioconcentration and metabolism of 4-tert-octylphenol in roach (Rutilus rutilus) fry

Early stages of fish have been reported to be particularly sensitive to the effects of xenoestrogens which may cause irreversible changes in sexual di fferentiation and development. In this study we report the uptake and metab olism of an oestrogenic alkylphenol, 4-tert-octylphenol (t-OP) in roach ( R utilus rutilus) fry. Roach fry, aged 7 days post hatch (DPH), were exposed to a concentration 5.8 +/- 0.8 mug/L of radiolabelled [C-14] t-OP in a semi -static system and were sampled 5, 12 and 19 days after exposure. After 5 d ays of exposure the bioconcentration factor (BCF) for t-OP residues was 346 ,whereas after 12 and 19 days of exposure steady state conditions in the fi sh were reached with BCFs of 1061 and 1134 respectively. Radio-HPLC analysi s of 7 DPH fry exposed for 5 days to t-OP revealed that the majority of res idues were present as the parent compound. However when 26 DPH fry were exp osed to t-OP for 5 days, t-OP only made up 22% of the total radioactivity, the remainder of which were a mixture of metabolites. The major metabolite was identified as the glucuronide conjugate of t-OP. This study suggests th at alkylphenols can bioconcentrate to high levels in larval fish but that r oach fry can rapidly conjugate them to more polar metabolites.