Effects of feeding status on biliary PAH metabolite and biliverdin concentrations in plaice (Pleuronectes platessa).

Relationships between feeding status and the biliary concentrations of biliverdin and metabolites of polycyclic aromatic hydrocarbons (PAH) have been investigated in plaice (Pleuronectes platessa) from the Firth of Clyde, Scotland. Plaice were caught at three times of the day, and kept, without feeding, in tanks for up to 24h. The mean concentrations of biliary PAH metabolites 2-OH naphthalene, 1-OH pyrene and 3-OH benzo-[a]-pyrene (3-OH B[a]P) were found to increase slightly over a 24h non-feeding period (only significant for 3-OH benzo-[a]-pyrene). This effect was not observed for mean biliary concentrations of 1-OH phenanthrene. During this period of starvation, bile volume, total amounts of all PAH metabolites in the gall bladder, and biliary biliverdin concentrations all significantly increased. No significant relationships (P>0.05) were found between indicators of feeding status and individual PAH metabolite concentrations, confusing the rationale for normalisation of data to account for differences in feeding status between fish. Normalisation of PAH metabolite concentrations to biliverdin concentrations did not consistently reduce the variance of the metabolite data for fish sampled after the same starvation period. However, the variation between mean metabolite concentrations of fish suffering different starvation periods was reduced by biliverdin normalisation for most of the metabolites measured. It is therefore recommended that biliary PAH metabolite data should be presented as raw concentrations, except in cases where there may be significant differences in feeding status between groups of fish. In such instances biliverdin normalised data should also be reported and observational guides such as bile volume and stomach contents may aid in the interpretation of data.