The kinetics of insecticide action. Part II: The relationship between the pharmacokinetics of substituted benzyl (1RS)-cis,trans-chrysanthemates and their relative toxicities to mustard beetles (Phaedon cochleariae fab.) |
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| Authors: | Martyn G Ford Richard Greenwood Peter J Thomas |
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| Abstract: | A mathematical model describing insect pharmacokinetics has been applied to data describing the penetration and elimination of a series of pyrethroid analogues the methylbenzyl (1 RS)-cis, trans-chrysanthemates], applied to mustard beetles. The three parameters of the model (kp, ke and λ) have been estimated for each compound. The influence of chemical structure on pharmacokinetics, investigated using canonical correlation analysis, is discussed in relation to relative toxicity and knockdown action. In general, physicochemical properties which result in a slow flow of insecticide through the insect are associated with high toxicity. A large proportion (84%) of the variation in relative toxicity has been explained by resistance to elimination (1/ke), implying that exposure of the site of action to insecticide is related to the total integral IM2 for material (M2) inside the insect. The remaining variation has been attributed to differences in behaviour at receptor sites. An optimum partition value (Δπ0 ≈ 1.6) seems necessary for maximum pharmacodynamic activity in this series of compounds. |
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