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 concent rations and exposure times on the biochemical responses of the earthworm Ei senia 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 i n sublethal assays for chemical testing in the laboratory. Thus, earthworms were exposed to increasing concentrations of B(a)P (50 mu g, 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 (CA T), acetylcholinesterase (AChE), glutathione-S-transferase (GST), methoxyre sorufin-O-deethylase (MROD), NADH (NADH Red) and NADPH (NADPH Red) cytochro me reductase activities, lipid peroxides (LP), peroxidizable lipids (LPI), total glutathione (total GSH) concentrations and percentage of oxidized glu tathione (%GSSG). Phase I enzyme activities and lipid peroxidation rates we re dependent both on the dose of B(a)P and on the duration of exposure. The se results showed that B(a)P could be metabolized either by P450-dependent activities or by the generation of free radicals. The responses were partic ularly sensitive as significant changes were detected at the lowest concent ration of B(a)P (50 mu g kg(-1) soil). A dear discrimination of the differe nt B(a)P concentrations was observed when the suite of biomarkers was inves tigated. 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. (C) 1999 Elsevier Science Ltd. All rights reserved.