engleski

The influence of imidacloprid and its transformation product 6-chloronicotinic acid on MXR activity in amphipod gammarus fossarum and earthworm eisenia fetida

The multixenobiotic resistance (MXR) defence system is mediated by different effl ux transporters and its activity has been confi rmed in many organisms, both prokaryotes and eukaryotes. MXR transporters confer resistance by preventing xenobiotics from entering the cells and by their extrusion into the extracellular environment. Chemicals known as chemosensitizers (inhibitors, modulators) can inhibit MXR function and thus represent specifi c environmental contaminants. A wide range of pesticides have been shown to act as MXR inhibitors. Presence of chemosensitizers in the environment may increase the absorption of xenobiotics and consequently their cellular toxic infl uence in aquatic and soil organisms. In this study, MXR activity and its inhibition have been measured using a dye exclusion assay in amphipod Gammarus fossarum and earthworm Eisenia fetida in order to assess the chemosensitizing potential of imidacloprid (IMI) and its transformation product 6-chloronicotinic acid (6CNA). In amphipods, 6CNA was proved to be a potent inhibitor of MXR at low concentrations, while IMI presented no signifi cant inhibition compared to control. Interestingly, co-exposure of amphipods to IMI or 6CNA and the common fungicide copper sulphate resulted in a greater additive inhibition effect of MXR activity. Earthworms exposed to tenfold lower concentration of IMI and 6CNA (because higher concentrations were lethal) did not exhibit inhibition of effl ux pumps. These results highlight the need of further investigation of the effects of neonicotinoids as chemosensitizers, as they enhance the toxicity of other co-occurring contaminants and may thus have signifi cant consequences for aquatic and soil organisms.

chemosensitizer; invertebrates; multixenobiotic resistance (MXR) defence system; neonicotinoids; rhodamine B

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