Debrisoquine 4-monooxygenase and bufuralol 1'-monooxygenase activities in bovine and rabbit tissues

The tissue distributions of debrisoquine 4-monooxygenase and bufuralol 1'-monooxygenase activities in microsomes from bovine and rabbit tissues were analysed. Debrisoquine 4-monooxygenase and bufuralol 1'-monooxygenase activities were found in liver, and at low levels in cerebral cortex, kidney cortex, lung, small intestine and spleen. Other tissues, such as kidney medulla, adrenocortex, adrenomedulla, blood vessels, thyroid gland, heart, ovary, uterus and testis, showed low levels of bufuralol 1'-monooxygenase activity but not detectable debrisoquine 4-monooxygenase activity. The bufuralol/debrisoquine monooxygenase activity ratios were higher in kidney and lung, and lower in cerebral cortex and spleen than in liver. Both monooxygenase activities in several bovine tissues including liver were inhibited strongly by phenylisocyanide (0.1 mM) and quinidine (0.5 mM), moderately by metyrapone (1 mM), and not at all by KCN (1 mM). NaN3 (5 mM) and sodium cholate (0.5% w/v) inhibited debrisoquine 4-monooxygenase activity strongly and moderately, but bufuralol 1'-monooxygenase activity moderately and strongly, respectively. No effect of a hydroxyl radical scavenger or of superoxide dismutase on either monooxygenase activity was observed. It was concluded from these results, as well as the NADPH dependency of the reactions, that the two monooxygenase reactions observed in these tissues were catalysed by cytochrome P450s.