Cytochrome P450 Monooxygenases in Larvae of Insecticide-Susceptible and -Resistant Strains of the Australian Sheep Blowfly, Lucilia cuprina

Abstract

The monooxygenase system of Lucilia cuprina larvae was examined using an insecticide-susceptible strain and strains selected with butacarb, deltamethrin, or diflubenzuron. Aldrin epoxidase activity in the butacarb-selected strain peaked when the larvae had attained their maximum weight and then decreased rapidly as the larvae wandered from their food medium. Activity was localized mainly in the midgut, malpighian tubules, and body wall. Cytochrome P450 levels and aldrin epoxidase activities in microsomal preparations were approximately 3-fold and 14-fold higher, respectively, in the deltamethrin-selected strain, and 4.5- to 5-fold and 30-fold higher, respectively, in the butacarb- and diflubenzuron-selected strains compared to the susceptible strain. Cytochrome b5 levels were 1.8-fold higher in each of the resistant strains relative to the susceptible strain. NADPH-cytochrome c reductase levels were up to 1.2-fold higher in crude extracts prepared from the resistant strains relative to the susceptible strain, it is likely that increased monooxygenase levels are implicated in the resistances shown by the insecticide-selected strains.