The plasma flux and oxidation rate of ornithine adaptively decline with restricted arginine intake

L. Castillo, M. Sánchez, T. E. Chapman, A. Ajami, J. F. Burke, Vernon R. Young

Research output: Contribution to journalArticle

56 Scopus citations

Abstract

We hypothesized recently that arginine homeostasis is achieved in humans largely by modulating the rate of arginine degradation. We have tested this hypothesis further by measuring in vivo the whole body rate of conversion of arginine to ornithine and ornithine oxidation in six healthy young adults. Subjects received for 6 days an L-amino acid-based diet supplying an arginine-rich or arginine-free intake and on day 7, following an overnight fast, an 8-h tracer protocol (first 3 h, fast state; next 5 h, fed state) was conducted; L-[guanidino-15N2; 5,5-2H]arginine and L-[5-13C]ornithine were given as primed, constant intravenous tracers; measurements of the abundances of various isotopologs of arginine, ornithine, and citrulline in plasma were made, and from these the various kinetic parameters of the metabolism of these amino acids were derived. Arginine and ornithine fluxes were significantly (P < 0.001) reduced in the fed state with arginine-free feeding. The rates of conversion (μmol · kg-1 · h-1; mean ± SD) of plasma arginine to ornithine for arginine-rich were 12.9 ± 2.6 and 24.7 ± 4.8 for fast and fed states. These values were 11.1 ± 3.5 and 9.6 ± 1.2 (P > 0.05 and P < 0.001), respectively, with an arginine-free diet. [13C]Ornithine oxidation was reduced (P < 0.001) by 46% during the fed state when the arginine-free diet was given. The findings strengthen our hypothesis that homeostasis of arginine metabolism in the human host depends importantly upon a regulation in the rate of arginine degradation with, perhaps, little involvement in the de novo net rate of arginine synthesis.

Original languageEnglish (US)
Pages (from-to)6393-6397
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume91
Issue number14
DOIs
StatePublished - Jul 5 1994

Keywords

  • adults
  • citrulline
  • degradation
  • diet

ASJC Scopus subject areas

  • General

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