MODES OF ACTION OF THE PLANT-DERIVED PHOTOTOXIN ALPHA-TERTHIENYL IN MOSQUITO LARVAE

The mode of action of the plant-derived phototoxic insecticide α-terthienyl (α-T), was examined in larvae of the mosquito Aedes aegypti (Linn.) (Diptera: Culicidae). Exposure of larvae to the toxin in the presence of near-ultraviolet light resulted in increased tissue levels of fluorescent breakdown products resulting from lipid peroxidation (LPO_. Control experiments confirmed that the fluorescent activity of α-T did not interfere with fluorometric determination of LPO products. Photosensitization by α-T had no significant effect on tissue levels of either total or reduced glutathione (GSH). However, levels of oxidized glutathione (glutathione disulfide) increased almost twofold as a result of α-T treatment in the presence of near-uv light. The role of LPO and GSH oxidation as indicators of mode of action of α-T and the possible role of antioxidant defense systems are discussed. © 1990.