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The metabolism of nitrosamines by microsomal cytochrome P-450 (P-450) isozymes was studied in a reconstituted monooxygenase system. P-450 LM2, LM3a, LM3b and LM3c, LM4, and LM6 were purified, respectively, from the livers of phenobarbital-treated, ethanol-treated, untreated, isosafrole-treated, and imidazole-treated rabbits. Of these isozymes, LM3a had the(More)
The nature of the denitrosation of nitrosamines by rat liver microsomes was investigated. The rates of NADPH-dependent nitrosamine demethylation and denitrosation were compared in the same incubation mixture using several types of microsomes and inhibitors. Pretreatment with isopropanol, pyrazole, phenobarbital, and 3-methylcholanthrene had parallel effects(More)
In order to elucidate the enzymic basis of nitrosamine metabolism, the in vitro metabolism of nitrosamines by rat liver microsomes and the effects of fasting on the microsomal enzymes have been studied. Fasting for 1 to 3 days causes a 2- to 3-fold enhancement of the reduced nicotinamide adenine dinucleotide phosphate-dependent nitrosodimethylamine(More)
Metabolism of nitrosamines was studied in a reconstituted monooxygenase system composed of cytochrome P-450 isozymes purified from liver microsomes of ethanol- and phenobarbital-treated rats. The ethanol-induced isozyme (P-450et) was efficient in catalyzing the demethylation of N-nitrosodimethylamine (NDMA), with a Km of 2.4 mM and Vmax of 7.2 nmol min-1(More)
The effects of acetone and isopropanol on the microsomal monooxygenase system have been investigated to study the role of this enzyme system in the metabolism of nitrosamines. Treatment of rats with acetone or isopropanol (2.5-5 ml/kg, i.g.) causes a 3-4.5-fold enhancement in the NADPH-dependent nitrosodimethylamine demethylase (NDMAd) activity. This is(More)
Results are presented to show that N-nitrosodimethylamine demethylase is P-450 mediated and N-nitrosodimethylamine is efficiently metabolized by specific P-450 isozymes inducible by a group of new inducers. The P-450-mediated N-nitrosodimethylamine demethylase also responds differently to inhibitors when activities are compared with those of classical(More)
The effects of ethanol on the metabolism of nitrosamines by rat liver microsomes have been studied. Treatment of rats with 10 or 15% ethanol in drinking water for 3 days causes a 4- to 5-fold enhancement in microsomal N-nitrosodimethylamine demethylase (NDMAd) activity and a 40-60% increase in gross P-450 content. The enhancement is mainly due to the(More)
The effects of riboflavin deficiency on the metabolism of N-nitrosodimethylamine [(DMN) CAS: 62-75-9] and other nitrosamines were examined in rats. After weanling rats were put on a riboflavin-deficient diet, the development of the deficiency was monitored by the growth rate and the erythrocyte glutathione reductase activation coefficient. In the(More)
The dynamics of tea catechins and organic acids in fermented fluid and yeast cells were studied. The concentration of eight kinds of catechins in solution decreased by 29.6–47.6%, respectively; some catechins were absorbed and accumulated by yeast cells, but the amount in the cells was very low during the fermentation process. The investigation of the(More)