Cytochrome P450 Monooxygenases in the Cotton Bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae): In Vivo Effects of Deltamethrin Exposure

The in vivo effects of deltamethrin on Helicoverpa armigera cytochrome 450s were investigated by the measurements of cytochrome P450 content and two enzymatic activities. Deltamethrin showed dose-, tissue-, and exposure way-specific effects on cytochrome P450 monooxygenases, ranging from induction to repression. Topical deltamethrin (0.1 and 1.0 g insect) significantly decreased cytochrome P450 contents with no changes in the examined activities with the exception of an increased p-nitroanisole Odemethylation in the midgut at low deltamethrin dose. However, topical deltamethrin exposure did not cause any changes in cytochrome P450 content and the examined monooxygenase activities in the fatbody microsomes. Feeding cotton bollworm larvae a diet containing deltamethrin (5 and 20 mg kg) for 2 days significantly increased total cytochrome P450s in the midgut and fatbody microsomes and enhanced p-nitroanisole O-demethylation in the midgut microsomes. Low-dose dietary deltamethrin slightly increased the activity of aldrin epoxidase in the midgut and fatbody. The differential effect of microsomal P450 monooxygenases by deltamethrin suggested the multiplicity of cytochrome P450 in this species. A comparison of the two exposure methods revealed that dietary deltamethrin exposure, especially at low dose, was more effective in the induction of the P450 system.