【目的】 为探讨亚致死浓度氰氟虫腙对小菜蛾Plutella xylostella（L.）3种解毒酶和细胞色素P450基因表达量的影响。【方法】 采用叶片浸渍法，测定用氰氟虫腙LC₁₀和LC₂₅处理72 h后小菜蛾羧酸酯酶、谷胱甘肽S-转移酶和多功能氧化酶3种解毒酶的活性；应用实时荧光定量PCR（Real-time PCR）方法测定了其在24、48和72 h时对P450基因（PxCYP4、PxCYP6和PxCYP9家族）表达的影响。【结果】 结果表明，氰氟虫腙LC₁₀和LC₂₅处理对羧酸酯酶活性影响不显著；对谷胱甘肽S-转移酶活性存在显著抑制作用（P<0.05）；LC₂₅处理后多功能氧化酶活性显著增加（P<0.05），为对照的1.39倍。同时，LC₂₅氰氟虫腙处理组小菜蛾P450基因PxCYP4M19、PxCYP6BF1V2、PxCYP6CN1和PxCYP6CV2 mRNA 的相对表达量分别为对照组的2.33~8.5倍、1.32~3.48倍、1.18~2.53倍、2.02~7.22倍。【结论】 结果显示，氰氟虫腙可能通过诱导这4种P450基因mRNA的上调表达而增强了小菜蛾多功能氧化酶酶活性。

     [Objectives]  To clarify the effects of sublethal concentrations of metafumizone, a novel sodium channel blocker insecticide, on the activities of detoxifying enzymes (carboxylesterase, glutathione S-transferase and function oxidase), and the expression of cycochrome P450 genes, in Plutella xylostella (L.). [Methods]  The activities of the three detoxifying enzymes and the mRNA expression levels of three P450 gene families (PxCYP4, PxCYP6 and PxCYP9) in P. xylostella were measured in 3rd instar larvae treated with sublethal doses of metafumizone (LC₁₀ and LC₂₅) via the leaf-dip bioassay method. [Results]  There was no significant difference in carboxylesterase (CarE) activity compared with the control, but glutathione S-transferase activity (GSTs) was distinctly inhibited by sublethal concentrations of metaflumizone (P<0.05). O-demethylation activities of mixed-function oxidases (MFOs) were significantly increased by sublethal concentrations of metaflumizone. When P. xylostella were treated with metaflumizone at LC₂₅ for 72 h, MFOs activity significantly increased (P<0.05) to 1.39-fold that of the control. The relative expression levels of PxCYP4M19, PxCYP6BF1V2, PxCYP6CN1 and PxCYP6CV2 after exposure to metaflumizone (LC₂₅) were, respectively, 2.33-8.5-fold, 1.32-3.48-fold, 1.18-2.53-fold, and 2.02-7.22-fold, those of the control. [Conclusion]  The results suggest that metaflumizone up-regulates the expression of four P450 genes and enhances the activity MFOs of in P. xylostella.