Culex quinquefasciatus Say from Saudi Arabia (Jpal-per) showed high levels of resistance (2,500-fold) to permethrin. A major contribution of cytochrome P450 monooxygenases as a mechanism of resistance was suggested by the large synergistic effects of oxidase inhibitors such as 2-propynyl 2,3,6-trichlorophenyl ether (PTPE) and piperonyl butoxide (PBO) on the toxicity of permethrin in the resistant strain. Contents of cytochrome P450 and b5 were about 2.5 times higher in the Jpal-per strain than those in the susceptible strain. P450 monooxygenase in the microsomes of gut and other parts of the body metabolized permethrin to 4′-HO-permethrin and other metabolites. Degradation of permethrin by microsomal P450 enzymes was much greater in the resistant Jpal-per strain and was inhibited by PBO and PTPE. In addition to a kdr type mechanism which seems to work in the larvae, cytochrome P450 monooxygenase is clearly shown to play an important role as a mechanism of permethrin resistance in Jpal-per strain larvae. Arch. Insect Biochem. Physiol. 37:47–56, 1998.
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Kasai et al. (1998) studied this question.
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