虱螨脲亚致死浓度对小菜蛾保护酶系和解毒酶系活力的影响
Effects of sublethal concentrations of lufenuron on endogenous protective and detoxifying enzymes in the diamondback moth, Plutella xylostella (L.)

为阐明虱螨脲对小菜蛾亚致死效应的生化机制,采用室内生物测定法测定了LC10和LC25亚致死浓度处理小菜蛾3龄幼虫1、6、12、24、48和72h后其体内保护酶系和解毒酶系的活力变化。结果表明:虱螨脲LC10处理对小菜蛾幼虫体内超氧化物歧化酶(SOD)活力表现为早期诱导、后期抑制的作用,而对过氧化物酶(POD)则表现为先抑制后诱导的作用,对过氧化氢酶(CAT)仅在72h时具有诱导作用;LC25处理对SOD表现为诱导-抑制-诱导-抑制的作用,对POD具有抑制作用,而对CAT具有诱导作用。经虱螨脲亚致死浓度处理后,小菜蛾幼虫体内酯酶和多功能氧化酶活力被明显抑制,且基本表现为浓度越高抑制作用越强;而谷胱甘肽S-转移酶(GST)活力仅在处理后1h被诱导,之后被显著抑制。表明虱螨脲进入小菜蛾幼虫体内后,初期可诱导SOD、CAT和GST活力升高,以适应外界毒害的影响;但随着时间的延长,3种解毒酶活力被抑制,使其难以代谢,从而增强了对小菜蛾的毒性。
In order to clarify the biochemical mechanism of sublethal effect of lufenuron in Plutella xylostella (L.), the activities of protective enzymes and detoxifying enzymes were determined after the third instar larvae ofP. xylostella treated for 1, 6, 12, 24, 48 and 72 h with LC10 or LC25 concentrations of lufenuron using cabbage leaf dipping method. The results showed that, under the treatment of LC10 concentration of lufenuron, the activity of superoxide dismutase (SOD) was induced firstly and then inhibited, while the activity of peroxidase (POD) was mainly inhibited firstly and then induced, and the activity of catalase (CAT) was only induced at 72 h after treatment; under the treatment of LC25 concentration of lufenuron, the SOD activity showed an induced-inhibited-induced-inhibited phenomenon, and the POD activity was inhibited while the CAT activity was induced obviously after treatment. Furthermore, the activities of esterase and mixed-function oxidase were inhibited significantly by sublethal concentrations of lufenuron and the inhibition increased as the concentrations increased, while the activity of glutathione S-transferase (GST) was only induced at one hour after treatment, and then inhibited significantly. Therefore, the SOD, CAT and GST activities of larvae could be firstly induced by sublethal concentrations of lufenuron, which made the diamondback moth become more tolerant to this insecticide, but when treatment time was prolonged, the activities of detoxification enzymes were inhibited, resulting in difficult metabolization of lufenuron, and thus increasing the toxicity to P. xylostella.