In vivo Effects of Cyfluthrin on Proteolytic Enzyme Activities of Malathion-resistant and Susceptible Strains of Triholium castaneum

摘要

To elucidate whether insecticide toxicity in insects involves insecticide-induced abnormalities of the intracellular protein catabolic process, we have determined the in vivo effect of a synthetic pyrethroid, cyfluthrin on the activities of representative protein catabolising cytoplasmic and lysosomal proteases (responsible for the various stages of the protein degradation cascade and essential for normal cell functioning) in resistant and susceptible strains of Tribolium castaneum. Effect of cyfluthrin was determined at LC50 after 48 hour of treatment both in the live and dead adult beetles and compared with controls. In treated live beetles, cyfluthrin decreased alanyl aminopeptidase (18%), arginyl aminopeptidase (6%), leucyl aminopeptidase (22%), tripeptidyl aminopeptidase (!2%), proline endopeptidase (43%) and dipeptidyl aminopeptidase I (23%) and increased cathepsin H (42%), while in dead beetles, almost all cytoplasmic proteases as well as cathepsin H manifested further decreasing trend. On the other hand in treated resistant strain live beetles, all lysosoma! proteases and leucyl aminopeptidase were considerably decreased ranging from 19% to 58% of control activity and this decreasing trend was further intensified in treated dead beetles, which ranged from 30% to 96%. We conclude that the effect of cyfluthrin on proteolytic enzyme activities induced inhibition of proteases and could be important in the development of insecticide resistance in T, castaneum.