Abstract
The relative contribution of the cytochrome P-450-dependent monooxygenase system ( P-450) and the FAD-containing monooxygenase (FMO) in the oxidation of phorate ( O,O-diethyl S-((ethylthio)methyl)phosphorodithioate) was investigated in liver, lung, and kidney microsomes isolated from male and female Dub:ICR mice. Selective inhibition was used to define the role of each enzyme system independent of the other system. Liver microsomes exhibited the greatest sulfoxidase activity, with P-450 responsible for greater than 75% of the activity. Although overall rates of sulfoxidation were much lower in lung and kidney microsomes, the FMO activity, relative to P-450, was greater. In all three organs, FMO activity appeared higher in microsomes isolated from female mice than microsomes from male mice. Phorate sulfoxide was the only metabolite detected during the linear range of the time course incubations. Extended time incubations yielded metabolites in addition to phorate sulfoxide in liver microsomes (phorate sulfone and phorate oxon sulfoxide) and lung microsomes (phorate oxon and phorate oxon sulfoxide), but not in kidney microsomes.
Published Version
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