Identificação do mecanismo de resistência à multixenobióticos (MXR) em Collembola (Arthropoda, Hexapoda)

Abstract

The Collembola class comprises a group of small arthropods, ranging from 0.12 mm to 12 mm, considered as basal hexapods, entognatha and aptera. They are used as indicators of disturbance and soil quality and are efficient indicators of the quality of the environment, because they respond quickly to the environmental changes. The species Folsomia candida is considered the standard species for ecotoxicological tests, however, the investigation of native species represents an interesting approach. The objective of the present work was to investigate the activity of the Mechanism of Resistance to Multixenobiotics (MXR) in the gut of 3 native species richly distributed in the country: Trogolaphysa sp., Cyphoderus similis and Cyphoderus innominatus. The MXR mechanism, already identified in several animal groups, is located in epithelia in contact with the external environment and uses carrier proteins to eliminate contaminants. In order to find the mechanism activity, in vitro tests were performed in the rodamine-B accumulation assay in the presence of verapamil hydrochloride, a known P-gp (P-glycoprotein) inhibitor, and MK571, a known MRP (multdrug related protein) inhibitor, both efflux pumps related to the MXR mechanism. In addition to the rhodamine-B accumulation assay, other tests were performed involving rhodamine-B in the presence of a heavy metal, the cadmium, to investigate the interaction of this metal with the MXR mechanism. Our results indicate the activity of efflux pumps in the intestines of three species of Collembola (C. similis, C. innominatus and Trogolaphysa sp.), being these pumps the basis of the Mechanism of Resistance to Multixenobiotics (MXR). We also find that, in C. similis and Trogolaphysa sp., increase in the mechanism activity in response to a very low concentration of a heavy metal widely found in contaminated soils, cadmium.