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

Eearly stages of fish have been reported to be particularly sensitive to the effects of xenoestrogens which may cause irreversible changes in sexual differentiation and development. In this study we report the uptake and metabolism of an oestrogenic alkyphenol, 4-tert-octylphenol (t-OP) in roach (Rutilus rutilus) fry. Roach fry, aged 7 days post hatch (DPH) were exposed to a concentration 5.8 ± 0.8 μg/L or radiolabelled [ 14 C] t-OP in a semi-static system and were sampled 5, 12 and 19 days after exposure. After 5 days 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 fish were reached with BCFs of 1061 and 1134 respectively. Radio-HPLC analysis of 7 DPH fry exposed for 5 days to t-OP revealed that the majority of residues were present as the parent compound. However when 26 DPH fry were exposed 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 that alkylphenols can bioconcentrate to high levels in larval fish but that roach fry can rapidly conjugate them to more polar metabolites.