The Effect Of N-acetylcysteine On Reducing Phoxim-Induced Toxicity On The Silkworm (Bombyx Mori)

Phoxim is one of the most widely used organophosphorus pesticides in China,and it is widely used in the prevention and control of agricultural and forestry pests for its broad spectrum,high efficiency,low toxicity and easy degradation.At the same time,it causes a certain degree of environmental pollution due to improper use.Bombyx mori is a classical model of Lepidoptera and is an important economic insect in the world.Silkworm breeding has a long history and extensive breeding area,in China.After a long period of artificial rearing and screening,the production of silk is increased gradually.Meanwhile,the phoxim causes a certain degree of environmental pollution due to improper use.Especially,sublethal dose of Phoxim,caused serious economic losses to silkworm industry,for silkworm is highly sensitive to pesticides.We selected hybrid silkworm Jingsong * Haoyue as research object.To explore the resistance of the phoxim poisoned Bombyx mori,we studied the growth and development（mortality,development time,body weight and body weight ratio）,physiological and biochemical indexes（Reduced glutathione content,total carbohydrate and protein content）,economic traits（single cocoon weight,cocoon shell weight,cocoon shell rate and reelable cocoon rate）and detoxification enzyme activities（Superoxide dismutase,carboxylesterase,GSTs enzyme,Phenoloxidase and Acetylcholinesterase）of Bombyx mori.The effect of N-acetylcysteine on the metabolism of Phoxim in silkworm larvae poisoned by phoxim was studied by HPLC,and the stability of N-acetylcysteine was determined.In this way,we built a new theoretical basis for detoxification of phoxim poisoning.According to this study,the following conclusions are drawn:（1）NAC can significantly alleviate the symptoms of silkworm phoxim poisoning（swing,crawl,spit liquid,and convulsions archoptosis）.Farthermore,it can improve the body weight,body weight ratio,survival rate and development time of phoxim poisoned silkworm.The average body weight of NAC treated group（2.028g）was significantly higher than phoxim poisoned group（1.849g）（p<0.05）.The body weight ratio of NAC pretreated group was normalized.After feeding NAC,the survival rate of silkworm infected with phoxim was increased from 81%±5% to 98%±5%,and it wassignificantly different（p<0.05）.The development time of phoxim poisoned silkworm has been extended by 25 h,after feeding NAC,the development time of phoxim poisoning silkworm was similar to that of the control group.（2）NAC can alleviate the adverse effects of Phoxim on Cocoon Quality.The single cocoon weight,cocoon shell weight,cocoon shell rate and reelable cocoon rate of NAC pretreatment（87.267%,1.763 g,0.363 g and 0.587%）was significantly higher than that of phoxim treatment（p<0.05）.The development time was significantly shortened in NAC pretreated group.（3）Compared to that of phoxim treated,NAC can relieve protein hydrolysis,carbohydrate consumption and inhibition of AChE enzyme activity.The activity of SOD was induced faster,the activity of ESTs was 1.64 folds and the activity of POD was recovered.In addition,NAC as the pro-drug of GSH enhanced GSH anabolism and induced the activity of GSTs.Especially this induction of GSTs was also occurred in the larvae of NAC treatment.NAC can enhance the resistance of silkworm 5th larvae for phoxim.（4）NAC can accelerate the flow and excretion of Phoxim in silkworm,the metabolic pathways of Phoxim in Bombyx mori are midgut,hemolymph,fat body and Malpighian tubules.NAC pretreatment can significantly shorten the time required for the metabolic link,Phoxim peak time of NAC treated group in the midgut,hemolymph and fat body and Malpighian tube were 0.5h,2h,4h and 4h,which were significantly lower than that of phoxim poisoned group 0.5h,4h,4h and 8h（p<0.05）.（5）We found that the mixed solution of NAC and nano TiO₂ were more stable.The mixed solution was tested at 6 months and 12 months,and the content of NAC was 87.786% and 15.048%,which was significantly higher than 30.643% and 5.762% of NAC solution.All of those provide scientific theoretical support for its application and production practice.