Insecticide uptake and decreased uptake resistance in the house fly (Diptera: Muscidae): A study with avermectin

We examined the pharmacokinetics of insecticide uptake and decreased uptake resistance to insecticides in the house fly Musca domestica, L. Flies were briefly exposed to low (2 ng) or high (200 ng) residues of [H-3]avermectin in glass vials and then transferred to clean vials. Adsorption occurred within 2 min and to a similar extent in susceptible and resistant flies. After transferring exposed flies to clean vials, much of the adsorbed avermectin was lost within 15 min and the loss was greater in resistant flies. In contrast, uptake of avermectin into the hemolymph was more extensive in susceptible flies. Preexposing flies to dinitrophenol blocked avermectin uptake and loss in both strains, suggesting avermectin transport may be facilitated by an adenosine triphosphate-dependent protein. When fasted flies were fed [C-14]glucose followed by exposure to avermectin, transport of [C-14]labeled derivatives of glucose to the cuticular surface was decreased relative to controls in both strains. These results suggest that the natural function of a protein that facilitates insecticide uptake is to transport hydrocarbons from the insect hemolymph to the cuticle and that quantitative or qualitative changes in the protein may relate to decreased uptake resistance.