Effects of hypoxia and phenobarbital treatment on the metabolism of mitomycin C in experimental animals.
To evaluate the effects of anaerobic conditions and inducers for the mixed-function oxidase system on the metabolism of mitomycin C, a bioreductive alkylating agent widely used for the treatment of hepatocellular carcinoma, experiments so designed were performed in rats and mice. Metabolism of mitomycin C by microsomes from normal rat liver and diethyl-nitrosamine-induced mouse hepatocellular carcinoma tissue was assessed from the disappearance of the quinone portion of mitomycin C and by measurement of alkylating metabolites using 4-(p-nitrobenzyl)pyridine as a trapping agent. The metabolism of mitomycin C measured by the two independent methods was strikingly increased under anaerobic conditions in both intact and tumor tissues. Since involvement of cytochrome P-450 in the metabolic activation of mitomycin C was shown recently, effects of representative inducers for the mixed-function oxidase system on the metabolism of mitomycin C were also studied. Phenobarbital treatment resulted in a significant increase in the metabolism of mitomycin C in both intact and tumor tissues under anaerobic conditions. The markedly enhanced formation of active metabolites of mitomycin C under anaerobic conditions may explain on a metabolic basis, at least in part, our recent clinical observations that chemoembolizations with microcapsular forms of mitomycin C is more effective than conventional bolus administration of this agent in the treatment of hepatocellular carcinoma. Combination of anaerobic conditions and induction of the mixed-function oxidase system may be applicable to chemotherapy of hepatic malignancy.
D000693:Anaerobiosis; D000818:Animals; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D008748:Methylcholanthrene; D051379:Mice; D008815:Mice, Inbred Strains; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D016685:Mitomycin; D008937:Mitomycins / Q000008:administration & dosage / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D008937:Mitomycins; D016685:Mitomycin; D008748:Methylcholanthrene; D006899:Mixed Function Oxygenases; D010634:Phenobarbital