engleski

Combination effect of pesticides on inhibiting multixenobiotic transporter P-glycoprotein in NIH 3T3/MDR1 mouse fibroblasts

The ABC transporter P-glycoprotein (P-gp) is a 170-kDa efflux pump which exports a diverse group of natural products, chemotherapeutic drugs, and hydrophobic peptides across the plasma membrane, driven by ATP hydrolysis. This transporter, in clinical medicine known as a part of multidrug resistant (MDR) phenomenon or in aquatic toxicology as a part of multixenobiotic resistant (MXR) mechanism, serves the same function and that is contribution to the selective pharmacological and toxicological barrier. When P-gp export activity is blocked by chemicals called chemosensitizers or modulators, higher accumulation of P-gp substrates occur with possible toxicological risk. Recently we have shown that pesticides endosulfan, phosalone, propiconazol and diazinon have potential to inhibit P-gp pump. The purpose of the present study was to assess do binary combinations of this four pesticides including model inhibitor verapamil express effect of additivity or synergism in inhibiting P-gp activity. Experiments were conducted using "P-gp accumulation" assay. NIH 3T3 mouse fibroblasts stabile transfected with MDR1 gene (NIH3T3/MDR1) which codes for P-gp accumulates a P-gp substrate calcein acetoxymethyl ester (Ca-AM) higher if the P-gp activity is blocked. Measured intracellular fluorescence of calcein is in the direct correlation with the state of the P-gp inhibition. Pesticide individual dose-response data were scaled and expressed as percent of maximum effect. Concentrations of each pesticide were added to the mixture at concentrations which produce the same inhibiting effect (isoboles). Based on the isobole method results were analysed indicating that diazinon in all combinations produce synergistic effect in inhibiting P-gp.

MXR; P-glycoprotein; calcein-AM assay; pesticides

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