The levels of cytochrome P450s, cytochrome b5, NADPH-cytochrome c (P450) reductase, and three indices of monooxygenase activities (methoxyresorufin O-demethylation (MROD), ethoxycoumarin O-deethylation (ECOD), and aryl hydrocarbon hydroxylation (AHH) were compared between one insecticide-susceptible and seven MFO-mediated insecticide-resistant house fly strains. Cytochrome b5 and P450 reductase were elevated by 1.2- to 2.2-fold and 1.5- to 2.3-fold, respectively, in the resistant strains compared with the susceptible. The level of cytochrome P450s was significantly increased (up to 2.1-fold) in all except two resistant strain compared with the susceptible strain. These results support the idea that all three monooxygenase components may play a role in insecticide resistance. Levels of MROD, ECOD, and AHH were significantly elevated (up to 180-fold) in nearly all cases. Pyrethroid resistance was generally correlated with MROD and AHH activities in all except one strain.
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Scott et al. (1990) studied this question.