| Susceptibility comparison of housefly(Musca domestica Vicina L.) susceptible and resistant populations to organophosphates and carbamates, and specific activity difference of acetylcholinesterase (AChE) of housefly in larvae, pupa ,and different body parts of adults, and change of the specific activity and susceptibility of AChE and change of the content of protein of susceptible housefly in different days after emergence were investigated systemically, and the effects of buffer in different pH values on the specific activity of AChE were studied, too. The condition of this enzyme to determine pesticide residual directly was optimized. The sensitivity, the minimal detected concentration and the recovery rates of pesticides which usually were misused in vegetables were tested, and were compared with the normal method of the state-chromatography, and the advantages and disadvantages of the AChE's inhibitory method in the rapid determination of pestiside residue were studied, the results were as follows:1. The results of the determination of susceptibility of susceptible and resistant housefly populations to organophosphates and carbamates showed that higher resistance had been occurred in the resistant housefly populations to dichlorvos and carbosulfan, and the LC50 to resistant populations was 12.90-fold, 10.26-fold compared with susceptible populations, respectively, and the I50 was 7.99-fold, 3.60-fold ,respectively. As a result, the AChE should be prepared from the susceptible housefly populations in the determination of pesticide residue by AChE's inhibitory method.The result of the assay of AChE in head, thorax, abdomen of housefly adults and diffent stages showed that the specific activity in the head was highest among the three parts of the adults body, and was 5.4-fold, 17.5-fold compared with thorax and abdomen, respectively. And it can be concluded that AChE activity was distributed mostly in the head. The specific activity of AChE in the head of male adults was higher than that in the head of female adults(1.2-fold), larvae(22.9-fold) and pupa(64.9-fold). Meanwhile, we found2. that AChE preparation from head was easier than thorax and abdomen, and the acquiring female adults was easier than male. Therefore, the results suggested that we should prepare AChE from adult heads, and should not differ the female and male in the study of the pesticide residue using housefly AChE.3. The results of the changes of the specific activity of AChE , susceptibility and the content of protein of susceptible housefly in different days after emergence, and the effects of buffer in different pH values on the activity of AChE showed that the specific activity of AChE in the head increased gradually(0.4483±0.0104～0.7769±0.0189μmol/mg?min) from the first day to the fifteenth day after emergence, while the content of protein decreased gradually(187.0222±9.0213～83.0222±7.1111μg/head). The susceptibility of AChE in the head was hightest from the second day to the fourth day after emergence, and the I50 of dichlorvos of the first day and the fifteenth day was 1.4 times and 2.1 times compared with that of the third day. The specific activity of AChE in the head increased with the increasing of the pH value within some scope(6.6-8.0). So, AChE of 2-4 days housefly after emergence should be prepared, and because most organophosphates and carbamates were decomposed easily in the alkalescence condition, the pH value of buffer should not be too high, and the optimal value was from 7.0 to 7.6.The results of the determination of the sensitivity and the minimal detected concentration of organophosphates and carbamates by AChE's inhibitory method showed that different pesticides had different inhibitory activity to AChE for their different chemical structures and function mechanisms. Among the pesticides detected, oxidative organophosphates had higher inhibitory ability, and the sensitivity by AChE's inhibitory method was higher and the minimal detected concentratin was lower.That was opposite to sulfureous fo...
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