Effects of the synergist piperonyl butoxide on metabolism of pesticides in green sunfish

The effects of piperonyl butoxide on metabolism of ¹⁴C-labeled methoxychlor, aldrin, and trifluralin were investigated in green sunfish, Lepomis cyanellus. Piperonyl butoxide inhibited epoxidation of aldrin to dieldrin, O-dealkylation of methoxychlor, and N-dealkylation of trifluralin, resulting in higher levels of total radioactivity in animals exposed to the combination compared to those exposed to pesticide alone. Where piperonyl butoxide was present a greater proportion of the total radioactivity in the fish extract occurred as parent compound compared to metabolites than in fish exposed to pesticide alone. After 16 days of exposure piperonyl butoxide increased the proportion of parent compound eight times for methoxychlor, 17 times for aldrin, and 15 times for trifluralin.