TY - JOUR T1 - In Vitro Metabolism of Fenthion and Fenthion Sulfoxide by Liver Preparations of Sea Bream, Goldfish, and Rats JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 179 LP - 186 DO - 10.1124/dmd.31.2.179 VL - 31 IS - 2 AU - Shigeyuki Kitamura AU - Tomoharu Suzuki AU - Tomoko Kadota AU - Mayumi Yoshida AU - Koji Ohashi AU - Shigeru Ohta Y1 - 2003/02/01 UR - http://dmd.aspetjournals.org/content/31/2/179.abstract N2 - The in vitro metabolism of fenthion and its sulfoxide (fenthion sulfoxide) in sea bream (Pagrus major) and goldfish (Carassius auratus) was investigated and compared with that in rats. Fenthion was oxidized to fenthion sulfoxide and the oxon derivative, but not to its sulfone, in the presence of NADPH by liver microsomes of sea bream, goldfish, and rats. These liver microsomal activities of the fish were lower than those of rats but were of the same order of magnitude. The NADPH-linked oxon- and sulfoxide-forming activities of liver microsomes of the fish and rats were inhibited by SKF 525-A, metyrapone, α-naphthoflavone, and carbon monoxide. The oxidizing activity to fenthion sulfoxide was also inhibited by α-naphthylthiourea. Several cytochrome P450 isoforms and flavin-containing monooxygenase 1 exhibited these oxidase activities. Fenthion sulfoxide was reduced to fenthion with liver cytosol of the fish and rats upon addition of 2-hydroxypyrimidine,N1-methylnicotinamide, or butyraldehyde, each of which is an electron donor of aldehyde oxidase, under anaerobic conditions. The activity was inhibited by menadione, β-estradiol, and chlorpromazine, which are inhibitors of aldehyde oxidase. The activities in the fish livers were similar to those of rat liver. Aldehyde oxidase purified from the livers of sea bream and rats exhibited the reducing activity. Thus, fenthion and fenthion sulfoxide are interconvertible in fish and rats through the activities of cytochrome P450, flavin-containing monooxygenase, and aldehyde oxidase. The American Society for Pharmacology and Experimental Therapeutics ER -