松墨天牛幼虫体内神经毒性酯酶和乙酰胆碱酯酶对甲胺磷敏感性的比较

Comparison of the sensitivity of neurotoxic esterase and acetylcholinesterase from Monochamus alternatus Hope larva to the inhibition by methamidophos

松墨天牛MonochamusalternatusHope是传播松材线虫BursaphelenchusxylophilusNickle的主要媒介昆虫,在其化学防治中经常使用有机磷杀虫剂,而这类杀虫剂有些可通过作用于神经毒性酯酶(neurotoxicesterase,NTE)使敏感的脊椎动物产生迟发性神经毒性。为了深入理解有机磷杀虫剂对害虫毒杀作用机理,增强对昆虫体内NTE活性的了解,我们在松墨天牛中开展了相关的研究。通过差异测定法和经典的乙酰胆碱酯酶(acetylcholinesterase,AChE)活性测定方法,分别测定了松墨天牛幼虫体内NTE和AChE的活性。结果发现,在松墨天牛体内存在NTE活性,其头部的NTE活力为2·80±0·30nmol·min-1·mg-1,比脂肪体高出了近10倍,但仍较鸟类等脊椎动物为低。体内实验显示,松墨天牛体内NTE可被甲胺磷所抑制;但在体外实验条件下,甲胺磷对来自松墨天牛头部的NTE活性并没有产生明显抑制作用,而此浓度下的甲胺磷对AChE表现出较高水平的抑制作用。表明松墨天牛体内NTE和AChE对甲胺磷的敏感性完全不同。

Monochamus alternatus Hope is a main insect vector of pinewood nematodes （ Bursaphelenchus xylophilus Nickle ）, which causes the serious pine wilt disease. Organophosphate is a kind of common insecticide used for the control of the pest insect. In birds and mammals, some organophosphates can cause a syndrome called organophosphate-induced delayed neurotoxicity by inhibiting neurotoxic esterase （NTE）. The activity of the enzyme was found in various organisms, but people know little about it in insects and especially its physiological functions at the present time. We detected the NTE activity in larva of M. alternatus by using the differential assay method, and found that the enzyme activity in the head was 2.80 ± 0.30 nmol· min^-1· mg , which was nearly 10 times that in the fat body of the insect, but much lower than that in birds and mammals. The NTE activity from the insect head could be inhibited by methamidophos in vivo ; however, in vitro, the NTE activity was found to be insensitive to methamidophos, which was quite different from that in birds and mammals.