title: 2,5-Diphenyloxazole as a probe for microsomal mono-oxygenation in human and rat liver.
abstract: 2,5-Diphenyloxazole (PPO) is metabolized to one major fluorescent product by human liver and rat liver microsomes. PPO metabolism by human-liver microsomes involves more than one cytochrome P-450 isozyme, termed low-affinity and high-affinity components. At a substrate concentration of 0.1 microM, 95% of activity is due to the high-affinity component whereas at 100 microM 69% of activity is due to the low-affinity component. Inhibition studies with metyrapone and alpha-naphthoflavone at 0.1 microM and 100 microM suggest that the high-affinity component may reflect a 3-methylcholanthrene-inducible form of cytochrome. Therefore studies at low substrate concentrations may be a useful tool for cytochrome P-450 studies in man. Rat liver microsomes show linear kinetics indicating the involvement of one major form of cytochrome P-450.
mesh_terms: D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008797:Metyrapone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism*; D010080:Oxazoles / Q000378:metabolism*; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats
chemical_list: D001571:Benzoflavones; D007527:Isoenzymes; D010080:Oxazoles; C011512:alpha-naphthoflavone; D003577:Cytochrome P-450 Enzyme System; C009012:2,5-diphenyloxazole; D010105:Oxygenases; D008797:Metyrapone