engleski

ACTIVITY OF MULTIXENOBIOTIC RESISTANCE (MXR) MECHANISM AFTER EXPOSURE TO NEONICOTINOID INSECTICIDE IMIDACLOPRID AND ITS TRANSFORMATION PRODUCT 6-CHLORONICOTINIC ACID IN AMPHIPOD Gammarusfossarum AND EARTHWORM Eiseniafetida

It is known that the multixenobiotic resistance (MXR) mechanism, mediated by the activity of membrane efflux transporters, represents a first line of defence in aquatic organisms exposed to environmental contaminants. MXR transporters prevent the cellular accumulation of potentially toxic xenobiotics by active export of parental or metabolised products of the contaminant out of the cell. There is a wide range of pesticides that act as chemosensitizers and inhibit MXR function with consequent increase of accumulated contaminants and their toxic effects inside an organism. The accumulation rate of a model MXR substrate, the fluorescent dye rhodamina B (RB), was used to investigate the MXR transport activity in aquatic amphipod G. fossarum and soil earthworm E. fetida stressed by neonicotinoid insecticide imidacloprid (IMI) and its transformation product 6- chloronicotinic acid (6CNA). In the case of amphipods this method showed a significant increase of RB accumulation in the presence of 6CNA at low concentrations, while IMI presented no significant inhibition compared to control. In addition, co-exposure of amphipods to IMI or 6CNA and the common fungicide copper sulphate resulted in a high cumulative inhibitory effect on MXR activity. In order to check modulatory effect of this pesticide on MXR activity in earthworms we exposed them to tenfold lower concentration of IMI and 6CNA (because higher concentrations were lethal). These concentrations did not exhibit inhibition of efflux pumps. Obtained data show the need for further investigation of neonicotinoid insecticides and its byproducts action as chemosensitizers since these effects may lead to increased toxicity of other present contaminants.

Multixenobiotic resistance (MXR); imidacloprid; 6-chloronicotinic acid; Gammarus fossarum; Eisenia fetida

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