Oxidative decarboxylation of benzoic acid by peroxyl radicals.

A chemical model based on the thermal decomposition of AAPH (2,2'-azobis(2-amidinopropane) dihydrochloride is used for the production of peroxyl radicals. Peroxyl radicals induces the decarboxylation of [7-13C]benzoic acid and the production of 13CO2, which is measured by gas chromatography-isotope ratio mass spectrometry (GC-IRMS). The decarboxylation depends on temperature, AAPH, and benzoic acid concentrations.

Continuous monitoring of 13C-aminopyrine metabolism in rats: effects of cold exposure and noradrenaline.

A system was developed to allow constant monitoring of hepatic cytochrome P450 activity in awake and unrestrained rats. A continuous 13C-aminopyrine perfusion was performed, and breath samples obtained for endogenous CO2 production and 13C measurements, to calculate 13C O2 production due to aminopyrine demthylation. Increasing doses of 13C-aminopyrine produced a hyperbolic increase of expired 13CO2, compatible with an in vivo measurement of enzymatic activity.

In vivo metabolism of aminopyrine by the larvae of the helminth Heligmosomoides polygyrus.

The in vivo N-dealkylation of [13C-2]-labeled aminopyrine by the L1-L2 larvae of Heligmosomoides polygyrus was demonstrated by the use of a sensitive gas chromatography-mass spectrometry method. This is the first evidence for the possible existence of a cytochrome P-450-dependent activity in helminths.

Reverse isotope dilution analysis of 13CO2 using gas chromatography/isotope ratio mass spectrometry: application to the quantitative determination of 13CO2 released by human polymorphonuclear leukocytes.

We propose a new method for the quantitative determination of carbon dioxide released by a biological microgenerator: a suspension of human polymorphonuclear leukocytes (PMNL). This method is based on the reverse isotope dilution analysis by gas chromatography/isotope ratio mass spectrometry of 13CO2 released by PMNL in a controlled isotope abundance atmosphere containing 3% CO2. 13CO2 release is effective after PMNL stimulation in the presence of [13C]glucose, labeled on positions 1, 2 or 6.

Evaluation of hydroxyl radicals production using 13CO2 gas chromatography-isotope ratio mass spectrometry.

A gas chromatography-isotope ratio mass spectrometry (GC-IRMS) technique for detecting the production of hydroxyl radicals is described. The decarboxylation of [7-13COOH]benzoic acid in the presence of a hydroxyl radicals source (a mixture of porphyrin and hydrogen peroxide) was followed by direct measurement of the 13CO2/12CO2 isotopic ratio. The production of hydroxyl radicals by the mixtures of porphyrin-hydrogen peroxide was proved by comparative study with electron spin resonance spectrometry and high-performance liquid chromatography analysis of hydroxylation products of benzoic acid.