表皮穿透和GABAA受体不敏感性在小菜蛾对阿维菌素抗性中的作用

用氚标记阿维菌素点滴处理阿维菌素敏感（ABM-S）和抗性（ABM-R）种群小菜蛾幼虫，结果显示，在5～360 min内的7个不同处理时间，ABM-R种群的平均表皮穿透量比ABM-S种群少1.5倍，处理24 h后，ABM-R种群仍有45.9%的3H-阿维菌素滞留于体表，而ABM-S种群却有98.4%的药剂穿透表皮。放射配体结合分析表明，GABAA受体结合性质的改变是小菜蛾对阿维菌素的另一抗性机制，ABM-S种群（K_d=10.9368±0.4374 nmol/L）和ABM-R种群（K_d=9.8328±0.3933　nmol/L）的受体亲和力无显著差异，但抗性种群的最大结合量（B_max=71.2842±4.9910　fmol/mg 蛋白）比敏感种群（B_max=112.0255±7.8418　fmol/mg 蛋白）降低63.6%，即抗性是受体数目的减少而非结构上的改变。

Cuticular penetration and desensitivity of GABAA receptor in abamectin resistant Plutella xylostella L.

The dynamics of topically applied ³H-abamectin to the fourth instar larvae was compared between the ABM-S and ABM-R strains. The results showed that during the period of 5 to 360 minutes, the number of ³H-abamectin penetrated the cuticular of ABM-R strain was 1.5-fold reduction to that of ABM-S strain. Treatment after 24h, the extraneous³H-abamectin still remained 45.9% in the ABM-R strain. While in the ABM-S strain, there was 98.4% of the ³H-abamectin penetrated the cuticular. Radioligand binding assay indicated that the change of GABAA receptor binding was also involved in abamectin resistance. Scatchard assay showed that there was no significant difference or receptor affinity between the ABM-S strain (K_d=10.9368±0.4374 nmol/L), and the ABM-R strain (K_d=9.8328±0.3933nmol/L). However, the maximum number of GABA_A receptor was decreased 63.6% in the ABM-R strain (B_max= 71.2842±4.9910 fmol/mg protein) compared with the ABM-S strain (B_max=112.0255±7.8418 fmol/mg protein). Therefore, the change of GABA_A receptor binding was caused by the reduction of receptor number, not the change of its molecular structure.