Pyrene metabolites in the hepatopancreas and gut of the isopod porcellio scaber, a new biomarker for polycyclic aromatic hydrocarbon exposure in terrestrial ecosystems

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Abstract
The object of this study was to investigate the formation of pyrene metabolites by the isopod Porcellio scaber as a possible tool in the environmental risk assessment of polycyclic aromatic hydrocarbon (PAH) exposure in terrestrial ecosystems. The formation of pyrene metabolites was studied after either pulse exposure to a single high dose, or prolonged exposure (14 d) to a lower dosage. Exposure studies were carried out with unlabeled or radiolabeled pyrene, ion pair chromatography was used for analysis, and reference conjugates were synthesized. We also measured pyrene metabolites in field—exposed animals, to explore their use as biomarkers of PAH exposure. Analysis of the hepatopancreas and gut of single isopods revealed the formation of five products, one of which was 1‐hydroxypyrene. Four of the remaining products were identified as phase II metabolites of 1‐ hydroxypyrene, with UV absorption and fluorescence characteristics similar to that of pyrene. One metabolite was identified as pyrene−1‐glucoside, which is in accordance with high rates of glucosidation, reported for these isopods. Another conjugate was identified as pyrene−1‐sulfate. None of the metabolites coeluted with a pyrene−1‐glucuronide reference obtained from fish bile. A fifth metabolite detected by on—line scintillation detection did not exhibit any absorption at 340 nm, possibly because one of the aromatic rings of pyrene had lost its aromatic character. Although pyrene is not known for its toxicity, it usually co—occurs with other PAHs that are transformed into toxic products. Investigating the metabolism of pyrene can provide information with regard to the biotransformation capacity of invertebrate species and uptake and elimination kinetics. Because pyrene is one of the most predominant PAHs in the environment, analysis of its metabolites provides an extra tool for the environmental risk assessment of ecosystems with regard to PAH exposure, bioavailability, and biotransformation.