| To detection the activity of acetylcholinesterase of housefly (Musca domestica), two methods were used, when the kinetic method was used, the optimum condition was: 0.02mol/L phosphate buffer with pH value of 7.4, 0.4 mmol/L 5,5' -dithiobis-(2-nitrobenzoic acid)(DTNB), 2mmol/L Achl. And when the terminal condition was: 0.02mol/L phosphate buffer with pH value of 7.4, 0.15mmol/LDTNB ehyl alchol solution, 6mmol/L AChI, 2 head/ml enzyme solution and react for 1 Omin.The sensitivity of three Musca domestica populations (Org, JS and NJ) to four organophosphrous and two carbamate insecticides were determined by glass vial bioassay method. The results showed that among the three populations, the laboratory population Org was most sensitive to all the insecticides tested except diazion, the NJ population was most insensitive. The sensitivity of AChE to methamidophos and methomyl were also tested, the results indicated that the AChE of Org was also more sensitive to the two insecticides than those of other two populations. These results demonstrated that the sensitivity of Musca domestica to organophosphates and carbamates determined by traditional bioassay method were closely correlated with the sensitivity of their AChE. Therefore, the sensitivity of AChE could be improved by breeding more sensitive housefly in laboratory. The preparation of susceptible housefly maybe speed up by selecting the parents from Org population.The susceptible population was selected 4 generations in this study. Comparing to the origin parent housefly, the LC50 values of the offspring to methamidophos and methomyl decreased, but the confidence limits overlapped. The IC50 of methamidophos and methomyl to AChE in the selected strains and original parent houseflies were also conducted. The results showed that the sensitivity of AChE weren' t improved significantly by single pair selection method, which is consistent to the bioassay results, that suggested that the Org population was very sensitive to methamidophos and methomyl, and it was difficult to get more sensitive offsprings by the traditional selection of single pair selection method.The sensitivities of AChE in different old housefly were also studied, the resultsshowed that the sensitivity of AChE to methamidophos and methomyl was most sensitive in the third day after emergence. The IC50 of methamidophos and methomyl to the AChE was 3.001 +0.03 lug/ml and 0.319+0.003ug/ml respectively. We also found that the specific activity of AChE in the head part was higher than those in other parts of the housefly. So AChE in the head part of 3-days old of housefly was used for pesticides residue determination.The inhibition rate of pesticides to AChE were determined under different temperature and reaction time. The results showed that the inhibition rate of methomyl to AChE was changed evidently with the inhibition time increased and it began to decrease after inhibition for 30s. While the inhibition rate of methamidophos increased all the time. The inhibition rate of methomyl decreased as the temperature going up, but the inhibition rate of methamidophos increased at the range of 25C to 35C, and reached the highest at 35C. Because the rapid and lower limit were required for detection the pesticide residue, and the organophosphate were maily used toxic pesticides, so the inhibition time and temperature were defined as 15 min and 35C respectively.The study revealed that the inhibition rate increased as the volume of pesticides increased, and when the volume was 0.4ml, the inhibition rate was ten percent more than that of 0.1 ml.The sensitivity and detection limit of commercial enzyme powdery and extracted crude liquid enzyme were compared by the rapid detection instrument and terminal method. Commercial enzyme powdery were more sensitive to methamidophos and methomyl than crude liquid enzyme, comparing with the commercial enzyme powdery, the detection limit of crude liquid to methamidophos was higher, to Methomyl, which was only 1.06 fold when the rapid detection instrument...
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