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 u ptake 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. Ad sorption 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 wa s greater in resistant flies. In contrast, uptake of avermectin into t he hemolymph was more extensive in susceptible flies. Preexposing flie s to dinitrophenol blocked avermectin uptake and loss in both strains, suggesting avermectin transport may be facilitated by an adenosine tr iphosphate-dependent protein. When fasted flies were fed [C-14]glucose followed by exposure to avermectin, transport of [C-14]labeled deriva tives of glucose to the cuticular surface was decreased relative to co ntrols in both strains. These results suggest that the natural functio n of a protein that facilitates insecticide uptake is to transport hyd rocarbons from the insect hemolymph to the cuticle and that quantitati ve or qualitative changes in the protein may relate to decreased uptak e resistance.