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Simultaneous detection of stable isotope-labeled and unlabeled L-tryptophan and of its main metabolites, L-kynurenine, serotonin and quinolinic acid, by gas chromatography/negative ion chemical ionization mass spectrometry

Abstract : A method for the detection of unlabeled and N-15(2)-labeled L-tryptophan (L-Trp), L-kynurenine (L-Kyn), serotonin (5-HT) and quinolinic acid (QA) in human and rat plasma by GC/MS is described. Labeled and unlabeled versions of these four products were analyzed as their acyl substitution derivatives using pentafluoropropionic anhydride and 2,2,3,3,3-pentafluoro-1-propanol. Products were then separated by GC and analyzed by selected ion monitoring using negative ion chemical ionization mass spectrometry. L-[C-13(11), N-15(2)]-Trp, methyl-serotonin and 3,5-pyridinedicarboxylic acid were used as internal standards for this method. The coefficients of variation for inter-assay repeatability were found to be approximately 5.2% for L-Trp and N-15(2)-Trp, 17.1% for L-Kyn, 16.9% for 5-HT and 5.8% for QA (n= 2). We used this method to determine isotope enrichments in plasma L-Trp over the course of a continuous, intravenous infusion of L-[N-15(2)] Trp in pregnant rat in the fasting state. Plasma N-15(2)-Trp enrichment reached a plateau at 120 min. The free Trp appearance rate (Ra) into plasma was 49.5 +/- 3.35 mu mol/kg/h. The GC/MS method was applied to determine the enrichment of N-15-labeled L-Trp, L-Kyn, 5-HT and QA concurrently with the concentration of non-labeled L-Trp, L-Kyn, 5-HT and QA in plasma. This method may help improve our understanding on L-Trp metabolism in vivo in animals and humans and potentially reveal the relative contribution of the four pathways of L-Trp metabolism.
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https://hal.inrae.fr/hal-02637804
Contributor : Migration Prodinra <>
Submitted on : Thursday, May 28, 2020 - 12:20:56 AM
Last modification on : Monday, June 21, 2021 - 5:26:02 PM

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Mitsue Sano, Véronique Ferchaud‐roucher, Charlotte Nael, Audrey Aguesse, Guillaume Poupeau, et al.. Simultaneous detection of stable isotope-labeled and unlabeled L-tryptophan and of its main metabolites, L-kynurenine, serotonin and quinolinic acid, by gas chromatography/negative ion chemical ionization mass spectrometry. Journal of Mass Spectrometry, Wiley-Blackwell, 2014, 49 (2), pp.128-135. ⟨10.1002/jms.3313⟩. ⟨hal-02637804⟩

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