alpha-Tocopherol antagonizes the toxicity of the pyrethroid insecticide permethrin in susceptible and kdr-resistant insects

Pyrethroid insecticides exert their toxic actions by prolonging the open ti me of individual neural sodium channels, alpha-Tocopherol (vitamin E) has r ecently been shown, via a patch clamp analysis of rat cells, to antagonize this action. To deterrnine if alpha-tocopherol could provide protection aga inst pyrethroids in vivo we examined the toxicity of a common pyrethroid (p ermethrin) against house flies and German cockroaches. Tocopherol antagoniz ed the toxicity of permethrin by 4.3- and 6.6-fold in house flies and Germa n cockroaches, respectively. alpha-Tocopherol also antagonized permethrin t oxicity by 6.2-fold in a kdr-type resistant strain of German cockroach (Le. strain having an altered form of the para-homologous sodium channel). Thes e studies indicate alpha-tocopherol is an effective antagonist of permethri n in vivo, protecting insects that have either normal or kdr-type sodium ch annels.