Hepatic and biliary biomarkers in rainbow trout injected with sediment extracts from the River Po (Italy)

Immature rainbow trout (Oncorhyncus mykiss) were injected i.p. with varying doses of extracts of sediments collected from the River Po (Northern Italy), upstream and downstream the immission of a heavily contaminated tributary (River Lambro). Six days after treatment, metabolic biomarkers were monitored in fish liver and bile. Microsomal enzyme activities, including arylhydrocarbon hydroxylase, ethoxyresorufin O-deethylase, aminopyrine N-demethylase and uridine-5′-diphosphoglucuronyltransferase, were induced by exposure to the polluted sediment to a moderate yet statistically significant extent, with dose-related effects. The cytosolic enzymes glutathione reductase, glutathione peroxidase and glutathione S-transferase were not affected by injection of sediment extracts, whereas both upstream and downstream specimens produced a depletion of nonprotein sulfhydryl groups. Elimination of fluorescent metabolites occured in the bile of trout injected with the polluted sediment extract, whereas organic extracts of bile were devoid of mutagenic activity in strain TA98 of S. typhimurium. In spite of some positive responses, the method used appears to be less sensitive in revealing the toxicological impact of pollution than either exposure of rainbow trout larvae to river sediment or in situ exposure of the same fish species in river water.