Absorption and metabolism of [14C]pyrethroids by the adult housefly, Musca domestica L., in vivo

Abstract

A natural mixture of pyre-throids, labeled biosynthetically with C14, was resolved by means of reversed-phase paper chromatography into chrysanthemic esters, pyrethric esters and unidentified non-insecticidal impurities. Allethrin labeled with C14 in the alcohol portion of the molecule, was prepared on the millimole scale at a specific activity of about 60 [mu]c/g of pure esters and purified by means of reversed-phase paper chromatography. Allethrin, the natural mixture of pyrethroids, or the chrysanthemic esters separated chromatographically was injected into or applied topically to adult houseflies. After a metabolism period the unchanged esters and their metabolites were extracted, resolved by paper chromatography and determined by radioactivity assay. Significant and comparable fractions of all the applied pyrethroids were metabolized to relatively non-insecticidal substances within 24 hours. When the synergist piperonyl cyclonene was applied simultaneously with the pyre-throid, the metabolism was substantially inhibited, but least effectively in the case of allethrin. This suggests that the synergism involved an interference with the natural detoxication mechanism of the housefly and leaves open the possible development of a more effective allethrin synergist. Absorption of the pyrethroids applied topically was almost complete with 24 hours and was apparently non-selective from an applied mixture of esters. The presence of piperonyl cyclonene invariably retarded absorption in 24 hours, presumably by dilution of the pyrethroid on the insect integument.