Metabolism of the phototoxin α-terthienyl in Culex tarsalis larvae: Involvement of the polysubstrate monooxygenase system

Metabolism of the plant-derived phototoxic insecticide, α-terthienyl (α-T), was examined in larvae of the mosquito Culex tarsalis Coquillett (Diptera: Culicidae). Results indicated that metabolism of [ 3H]α-T occurred and that the resulting hydrophilic metabolites were the principal products excreted from 1-hr post-treatment onward. Pretreatment of larvae with piperonyl butoxide increased susceptibility to α-T phototoxicity and decreased the extent of [ 3H]α-T elimination as compared to controls. Pretreatment with β-naphthoflavone reduced α-T toxicity without affecting its elimination. Phenobarbital pretreatment affected neither toxicity nor elimination of the phototoxin. A model for interaction of Phase I and Phase II systems in metabolism of α-T by C. tarsalis larvae is proposed.