Mechanism of the Reduction of Fenitrothion Toxicity in Kuruma Prawn by Piperonyl Butoxide

A study on the relation between the toxicity of fenitrothion (FS) and its metabolism in kuruma prawn Penaeus japonicus treated with piperonyl butoxide (PB) was performed to elucidate the cause of the remarkable reduction of FS toxicity in the prawn by PB treatment, using ₁₄C labeled FS. The PB treatment did not affect FS absorption by the prawn from media, but it considerably inhibited the biotransformation of FS to fenitrooxon (FO), i.e. the reduction of FS toxicity in the prawn by PB treatment was attributed to the decrease in FO formation. The minimum lethal concentration of FO in the prawn was presumed to be 10–14 pmol/g, whereas that of FS was higher than 400 pmol/g. According to the amounts of FS and its metabolites found in kuruma prawn treated with and without PB, the main metabolic pathway of FS in the prawn was presumed to be FS→FO→desmethylfenitrooxon→3-methyl-4-nitrophenol→its conjugates.