Biochemical responses of the earthworm Eisenia fetida andrei exposed to contaminated artificial soil: effects of benzo(a)pyrene

We investigated the effects of benzo(a)pyrene (B(a)P), at different concentrations and exposure times on the biochemical responses of the earthworm Eisenia fetida andrei to (1) elucidate the mechanisms of action of polycyclic aromatic hydrocarbons (PAHs) and (2) explore the potential for using these responses as biomarkers for monitoring PAH-contaminated soils or for use in sublethal assays for chemical testing in the laboratory. Thus, earthworms were exposed to increasing concentrations of B(a)P (50 μg, 1 mg, 100 mg and 1 g kg−1 artificial soil) for 1, 2, 7 or 14 d using the standard soil test method. The following biochemical factors were measured: catalase (CAT), acetylcholinesterase (AChE), glutathione-S-transferase (GST), methoxyresorufin-O-deethylase (MROD), NADH (NADH Red) and NADPH (NADPH Red) cytochrome reductase activities, lipid peroxides (LP), peroxidizable lipids (LPI), total glutathione (total GSH) concentrations and percentage of oxidized glutathione (%GSSG). Phase I enzyme activities and lipid peroxidation rates were dependent both on the dose of B(a)P and on the duration of exposure. These results showed that B(a)P could be metabolized either by P450-dependent activities or by the generation of free radicals. The responses were particularly sensitive as significant changes were detected at the lowest concentration of B(a)P (50 μg kg−1 soil). A clear discrimination of the different B(a)P concentrations was observed when the suite of biomarkers was investigated. These biochemical responses measured in E. fetida andrei could be used together in sublethal assays for chemical testing in the laboratory or for soil contamination surveys.