RESUMEN
Pyridinol carbamate was nitrosated to the N,N1-dinitroso derivative and the structure was proved by spectroscopic methods, including chemical ionization mass spectroscopy. By the Ames test, the dinitroso derivative showed a significant dose-dependent mutagenic response with Salmonella typhimurium strains TA 1535 and TA 100; the response became more pronounced in the presence of microsomes. As the dosage of N-nitroso pyridinol carbamate increased, the number of revertant colonies also increased. Pyridinol carbamate was not mutagenic.
Asunto(s)
Carbamatos , Mutágenos , Nitrosaminas/farmacología , Piridinolcarbamato , Animales , Carbamatos/análogos & derivados , Evaluación Preclínica de Medicamentos , Técnicas In Vitro , Hígado/efectos de los fármacos , Hígado/metabolismo , Piridinolcarbamato/análogos & derivados , Piridinolcarbamato/metabolismo , Piridinolcarbamato/farmacología , RatasRESUMEN
A sensitive, specific GLC assay was developed for the determination of ethinamate in plasma and its major metabolite, trans-4-hydroxyethinamate, in urine. The assay uses a mass internal standard of dimethylethinamate. Ethinamate is extracted from alkalinized plasma with dichloromethane. Urine samples require beta-glucuronidase hydrolysis prior to extraction of hydroxyethinamate. The dichloromethane is removed by evaporation, and the compounds are measured by GLC using a flame-ionization detector. By using GLC-chemical-ionization mass spectrometry, the compounds measured were identified as the intact ethinamates. Plasma and urine data are presented from a bioavailability study to demonstrate the utility of this method. From these data, the ethinamate plasma half-life was calculated as 1.9 +/- 0.3 hr.
Asunto(s)
Carbamatos/análisis , Disponibilidad Biológica , Cápsulas , Carbamatos/análogos & derivados , Carbamatos/metabolismo , Cromatografía de Gases , Humanos , Espectrometría de Masas , Solubilidad , ComprimidosRESUMEN
Some preparations of both native aspartate transcarbamylase from Escherichia coli and catalytic subunit have fewer tight binding sites per oligomer for carbamyl-P than the number of catalytic peptide chains. In contrast, the number of sites for the tight-binding inhibitor N-(phosphonacetyl)-L-aspartate does equal the number of catalytic chains in each case. Binding of the labile carbamyl-P was determined using rapid gel filtration, with conversion to stable carbamyl-L-aspartate during collection. Native enzyme (six catalytic chains) obtained from cells grown under the conditions of J.C. Gerhart and H. Holoubek (J. Biol. Chem. (1967) 242, 2886-2892) has 5.4 tight sites for carbamyl-P at pH 8.0 (KD = 9.9 muM), whereas native enzyme from cells grown with higher concentrations of glucose, uracil, and histidine (to yield more enzyme per unit volume of culture) has only 1.9 tight sites at pH 8.0 (KD = 4.6 muM) and only 2.3 tight sites at pH 7.0 (KD = 2.6 muM). At pH 8.0, catalytic subunit (three catalytic chains) obtained from the former native enzyme has 2.2 tight sites for carbamyl-P (KD = 2.4 muM) and the number of sites is 2.3 in the presence of 35 mM succinate, whereas catalytic subunit obtained from the latter native enzyme has 1.8 tight sites (KD = 3.6 muM) in the absence of succinate and 2.3 tight sites in its presence. The number of tight binding sites is also less than the number of subunit peptide chains in 19F nuclear magnetic resonance experiments performed with catalytic subunit and two fluorinated analogs of carbamyl-P at comparable concentrations of analogs and active sites. A model is proposed in which incomplete removal of formylmethionine from the NH2 termini of the enzyme under conditions of extreme depression affects affinity for ligands.