Whole-body metabolism of the organophosphorus pesticide, fenthion, in goldfish, Carassius auratus

The in vivo metabolism of fenthion, an organophosphorus pesticide, and its sulfoxide (fenthion sulfoxide) was examined in goldfish (Carassius auratus). When goldfish were administered fenthion i.p. at a dose of 100 mg/kg, two metabolites were isolated from the tank water. They were identified as fenthion sulfoxide and fenthion oxon, in which >P=S of fenthion is transformed to >P=O, by comparing their mass and UV spectra, and their behavior in HPLC and TLC, with those of authentic standards. However, fenthion sulfone was not detected as a metabolite. The amounts of fenthion, fenthion sulfoxide and fenthion oxon excreted within 4 days were 2.7, 3.4 and 2.5% of the initial dose of fenthion, respectively. Unchanged fenthion was detected in the body of the fish to the extent of 42–50% of the dose after 10 days, but fenthion sulfoxide and fenthion oxon showed very low concentrations. When fenthion sulfoxide was administered to the fish, about 70% of the dose was excreted unchanged into the tank water within 24 h, but little of the reduced compound, fenthion, was found. In contrast, fenthion was detected at 2.1% of dose in the body of goldfish as a metabolite of fenthion sulfoxide. The fact that fenthion is metabolized to the toxic oxon form in fish presumably has environmental and health implication for its use as a pesticide.