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  • Title: Studies on the O-demethylation of misonidazole by rat liver microsomes.
    Author: Shoemaker DD, McManus ME, Hoerauf R, Strong JM.
    Journal: Cancer Treat Rep; 1982 Jun; 66(6):1343-7. PubMed ID: 7083238.
    Abstract:
    The role of rat liver microsomes in the O-demethylation of misonidazole to desmethylmisonidazole was studied. The rate of the microsomal-dependent formation of desmethylmisonidazole was linear up to a protein concentration of 2 mg/ml and over a 10-minute interval. The metabolism was optimal in a system comprised of microsomes, O2, and NADPH. Metabolism in incubation mixtures continuously flushed with N2 was inhibited by 78%. The O-demethylase activity was competitively inhibited by the addition of SKF 525-A, with a Ki of approximately 1 x 10(-5) M. The Km and Vmax values of normal microsomes were 1.87 +/- 0.30 mM and 413 +/- 14 pmols/minute/mg of microsomal protein, respectively. Pretreatment of rats with phenobarbital for 7 days prior to preparation of the microsomes resulted in no significant change in the Km, but the Vmax was considerably increased to 1033 +/- 203 pmols/minute/mg of microsomal protein. The results demonstrate that the O-demethylation of misonidazole is mediated by cytochrome P-450.
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