论淡色库蚊敌百虫抗性品系的抗药性机理

分别测定了淡色库蚊(Culex pipiens pallens)敏感品系(SEN)及敌百虫抗性品系(RD)雌成蚊的乙酰胆碱酯酶(AchE)对硫代乙酰胆碱(Atch)的米氏常数(K_m)和最大反应速度(V_max).SEN雌成蚊头部AchE的K_m=1.2×10^-4mol/L,V_max=7.7×10^-3mol/L(产物);胸部的K_m=0.8×10^-4mol/L,V_max=6.5×10^-3mol/L(产物).RD雌成蚊头部AchE的K_m=5.7×10^-4mol/L,V_max=25×10^-3mol/L(产物);胸部的K_m=0.8×10^-4mol/L,V_max=9.5×10^-3mol/L(产物).结果表明:1.SEN和RD二者的雌成蚊,它们自身头、胸间AchE是不同质的,是以同工酶的形式存在,因此RD雌成蚊头部AchE的性质与SEN雌成蚊的头部有显著差异也是由AchE同工酶的变异所造成.2.RD雌成蚊头部AchE在量上与SEN间也存在明显的差异.因此可以认为RD雌成蚊对有机磷产生抗性的主要机理是头部AchE在质和量上产生了变异.由于羧酸酯酶不是对具有磷酸酯键的有机磷制剂作用的靶子酶,因而不是敌百虫抗性产生的主要原因.

ON THE MECHANISM OF DIPTEREX RESISTANCE IN CULEX PIPENS PALLENS COQ.

The activity of acetylcholinesterase (AchE) in the female adults of the susceptible strain (SEN) and resistant strain (RD) of Culex pipens fallens Coq, was determined. By comparing the values of Km and Vmax of the enzymic activity in the two strains, we draw the following conclusions:The head AchE, is structurally different from the thoracic AchE in the both strains. Structural difference exists also in the head AchE of RD and SEN, but not in the thoracic AchE of the two strains. The Vmax of the head AchE activity of RD is about two times higher than that of SEN, but that of thoracic AchE of RD is only half that of SEN. Therefore the major mechanism of resistance towards organic phosphorus insecticides of RD resides in the structural and quantitative variation in the head AchE.The RD has an acid phosphatase activity equal to that of the SEN, but it contains the enzyme malathion-carboxylesterase which displays the following two characteristics: (1) It can hydrolyze malatblon and other compounds containing carboxylic bond but not phosphatester bond. (2) It contributes to the resistance of RD towards the insecticides by its absorptive effect. These characteristics make the resistance of the RD belong to the weak type. Therefore the enzyme does not play a major role in the resistance mechanism of that strain.