Reductive Dechlorination of p, p'-DDT Mediated by Hemoproteins in the Hepatopancreas and Blood of Goldfish, Carassius auratus

Abstract

The in vitro metabolism of p, p'-DDT (p, p'-dichlorodiphenyltrichloroethane), an important environmental pollutant, was examined in fish, focusing on reductive dechlorination. When p, p'-DDT was incubated with hepatopancreas microsomes or the blood of goldfish, Carassius auratus, in the presence of both a reduced pyridine nucleotide and FMN, a dechlorinated metabolite, p, p'-DDD (p, p'-dichlorodiphenyldichloroethane) was formed under anaerobic conditions. These reductase activities were inhibited by carbon monoxide. Although the microsomes or blood was boiled, the dechlorinating activity was not abolished. Hemoglobin and hematin exhibited the reductase activity toward p, p'-DDT with NADH and FMN. The activity of hematin was also exhibited with FMNH₂. The reductive dechlorination appears to proceed nonenzymatically by the reduced flavin, catalyzed by the heme group of hemoproteins.