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Styrene monooxygenase and epoxide hydratase activities were studied in the hepatic and extrahepatic microsomal fractions of male and female rats, mice, guinea pigs and rabbits. The highest specific acitivity of both enzymes was present in the liver where levels of epoxide hydratase were higher than monooxygenase. The two enzyme systems are present in all the tissues of both sexes of the species considered. A particularly high ratio of monoxygenase to hydratase activities was found in mouse and rabbit lungs.

Male rat liver intact nuclear preparations are able to metabolize adriamycin to reactive species that irreversibly interact with nuclear DNA and proteins in the presence of reduced NADPH. This process was not inhibited by 1 mM SKF-525A, suggesting that a nuclear monooxygenase enzymatic system was not involved.

The plasma kinetics and urinary elimination of saccharin were studied in 3 groups each of 5 healthy male volunteers given the sweetener as three different single oral doses (50, 150 and 333 mg 60 kg body weight). Saccharin concentrations were determined by gas liquid chromatography-stable isotope dilution mass fragmentography. The compound was rapidly absorbed through the gastrointestinal tract, reaching plasma peak concentrations between 30 and 60 min after intake. Plasma saccharin elimination was also fast, with a monoexponential pattern of decay. At the 3 doses studied saccharin was excreted in urine within a few hours, about 60% of the dose being excreted unchanged at 6 h and 76% at 24 h.

Caffeine metabolism to 6-amino-5-[ N -methylformylamino]-1,3-dimethyluracil was studied in the isolated, perfused rat liver. The [2- 14 C]-labelled drug and metabolites were separated by thin-layer chromatography or high-pressure liquid chromatography. The chemical structure of 6-amino-5-[ N -methylformylamino]-1,3-dimethyluracil was confirmed by mass spectrometry and it was quantitatively determined by liquid scintillation counting. 6-Amino-5-[ N -methylformylamino]-1,3-dimethyluracil is one of the major metabolites of caffeine found in the perfusion medium. The kinetics of caffeine elimination and of the uracil metabolite formation were studied up to 2 h perfusion time using livers from control rats and rats pretreated with phenobarbital, β-naphthoflavone or 3-methylcholanthrene. Phenobarbital pretreatment did not modify the rate of caffeine elimination or the extent of 6-amino-5-[ N -methylformylamino]-1,3-dimethyluracil formation. In contrast, there was a highly significant inducing effect on both drug elimination and formation of the uracil metabolite in perfusions of livers from β-naphthoflavone- and 3-methylcholanthrene-pretreated animals.