These studies examined the effect of dicumarol on xanthine dehydrogenase (XDH), an enzyme recently shown to bioreduce mitomycin C. Dicumarol, which has previously been shown to inhibit xanthine oxidase (XO), inhibited both XDH and XO mediated conversion of xanthine to uric acid but potentiated the metabolism of mitomycin C by XDH and XO. Formation of 2,7-diaminomitosene following mitomycin C bioactivation by XDH was increased 3-fold aerobically and 4-fold hypoxically when 20 µm dicumarol was included in the reaction mixture. XO mediated metabolism of mitomycin C hypoxically was increased approximately 50% by the inclusion of dicumarol.

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This work was supported by USPHS Grant CA-43660 from the National Cancer Institute and by the Reno Cancer Center.

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