• Culex pipiens;
  • Cx. quinquefasciatus;
  • ATP-binding;
  • calcium channel blocker;
  • cell culture;
  • chlorpyrifos;
  • cypermethrin;
  • DDT;
  • endosulfan;
  • insecticides;
  • ivermectin;
  • mosquitoes;
  • organophosphate;
  • p-glycoprotein;
  • pyrethroid;
  • resistance;
  • rhodamine;
  • vector control;
  • verapamil;
  • vinblastine

Abstract Pesticide resistance has parallels with multi-drug resistance syndrome of tumours in clinical medicine, which has been linked to an ATP-dependent pump, p-glycoprotein (P-gp). P-gps pump drugs out of the cell, thereby reducing cellular concentrations of the chemical. P-gps have been found in several invertebrate species and have been shown to provide a defence against environmental xenobiotics, including pesticides.

This study used a model cell culture system to investigate the interaction of pesticides with P-gp. Ivermectin and endosulfan were shown to be strong inhibitors of dye transport out of cells, which is a standard measure of P-gp modulation. We then investigated the action of a P-gp inhibitor, verapamil (calcium channel blocker), on insecticide toxicity to fourth-instar mosquito larvae of the Culex pipiens L. complex (Diptera: Culicidae). Verapamil increased toxicity to examples of three insecticide classes (cypermethrin, endosulfan, ivermectin), but not to chlorpyrifos (organophosphate).

The discovery of a novel protective mechanism in mosquitoes, with a wide substrate range, has implications for the control of important pest and vector species.