Determination of Isotope Enrichment in<sup>13</sup>C-or<sup>2</sup>H-Labelled Branched-Chain l-Amino Acids From Physiological Fluids by Gas Chromatography-Mass Spectrometry: Use of l-Leucine Dehydrogenase for Specific Preparation of the Quinoxalinol Derivatives

A seven compartment model was applied for evaluation of oral L-[1-(13)C]leucine loading tests (38 μmol/kg body wt.) in healthy volunteers. The model comprises transport and absorption in stomach and gut into a central L-leucine-compartment which is connected to a protein compartment and to the compartment of the corresponding 2-oxo acid. CO(2) release from the latter occurs in a fast and a slow compartment into the central CO(2) compartment for exhalation. Using the fmins routine of MATLAB for parameter estimation, a good agreement was obtained between calculated and actually measured kinetics of (13)C-labelled metabolites and a mean in vivo L-leucine oxidation of 0.365 ± 0.071 μmol/kg per min (n = 5) was computed. Plausibility of the model was checked by predicting in vivo leucine oxidation rates from primed continuous infusion tests (priming: L-[1-(13)C]leucine, 5 μmol/kg; NaH(13)CO(2), 1.2 μmol/kg; infusion: L-[1-(13)C]leucine, 5 μmol/kg per h). In 5 tested volunteers, the experimental L-leucine oxidation rate amounted to 0.358 ± 0.105 μmol/kg per min versus predicted 0.324±0.099 μmol/kg per min. Possible causes for some observed intraindividual variations are discussed.

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Determination of Isotope Enrichment in¹³C-or²H-Labelled Branched-Chain l-Amino Acids From Physiological Fluids by Gas Chromatography-Mass Spectrometry: Use of l-Leucine Dehydrogenase for Specific Preparation of the Quinoxalinol Derivatives

Cited by 3 publications

References 37 publications

Analytical Aspects of Amino, Quaternary Ammonium, Nitro, Nitroso and Related Functional Groups

Analytical Aspects of Amino, Quaternary Ammonium, Nitro, Nitroso and Related Functional Groups

Determination of¹³C Enrichment by Conventional GC-MS and GC-(MS)-C-IRMS

Compartmental Approach for Evaluation of Plasma Kinetics and¹³Co₂-Exhalation after Oral Loading with L-[1-¹³C]Leucine

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Determination of Isotope Enrichment in13C-or2H-Labelled Branched-Chain l-Amino Acids From Physiological Fluids by Gas Chromatography-Mass Spectrometry: Use of l-Leucine Dehydrogenase for Specific Preparation of the Quinoxalinol Derivatives

Cited by 3 publications

References 37 publications

Analytical Aspects of Amino, Quaternary Ammonium, Nitro, Nitroso and Related Functional Groups

Analytical Aspects of Amino, Quaternary Ammonium, Nitro, Nitroso and Related Functional Groups

Determination of13C Enrichment by Conventional GC-MS and GC-(MS)-C-IRMS

Compartmental Approach for Evaluation of Plasma Kinetics and13Co2-Exhalation after Oral Loading with L-[1-13C]Leucine

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Determination of Isotope Enrichment in¹³C-or²H-Labelled Branched-Chain l-Amino Acids From Physiological Fluids by Gas Chromatography-Mass Spectrometry: Use of l-Leucine Dehydrogenase for Specific Preparation of the Quinoxalinol Derivatives

Determination of¹³C Enrichment by Conventional GC-MS and GC-(MS)-C-IRMS

Compartmental Approach for Evaluation of Plasma Kinetics and¹³Co₂-Exhalation after Oral Loading with L-[1-¹³C]Leucine