Biomarker responses in Lumbricus terrestris exposed to model drugs

Abstract

The earthworm Lumbricus terrestris, is a common anecic key species in natural soils used also as bioindicator in soil pollution assessment. Specimens of L. terrestris were exposed in Petri dishes to filter paper embedded with 1 mg/mL to different model compounds for 48 h. The chemicals were: Lamotrigine, Cocaine, Fipronil (as Regent¿800WG) and the organophosphorus pesticide bis-4-nitrophenyl phosphate (BNPP). At the end of this period, earthworms were immediately frozen in liquid N2 and their tissues, homogenized by cryogrinding, targeted to determine chemical exposure and metabolite formation as well as to biomarker determinations. The biomarkers analyzed were the activities of the enzymes Acetylcholinesterase (AChE), Glutathione-S-transferase (GST) and Carboxylesterase (CES) using different substrates. The results obtained revealed differences in enzymatic activity among substrates, being CE activities with the substrates 4-nitrophenyl butyrate (4-NPB) and 1-naphthyl butyrate (1-NB) the most responsive to cocaine and BNPP. These results for BNPP, corroborate data obtained after in vitro exposure. This study highlights the utility of long chain butyrate esters in CE measures in invertebrate and the agreement between in vivo and in vitro responses in L. terrestris. Chemical analysis and metabolite formation should confirm the extent of the exposure and other range of concentrations should be used to assess any dose-response effects