Glutamine and leucine nitrogen kinetics and their relation to urea nitrogen in newborn infants

Prabhu S. Parimi, Srisatish Devapatla, Lourdes Gruca, Alicia M. O'Brien, Richard W. Hanson, Satish C. Kalhan

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15 Scopus citations


Glutamine kinetics and its relation to transamination of leucine and urea synthesis were quantified in 16 appropriate-for-gestational-age infants, four small-for-gestational-age infants, and seven infants of diabetic mothers. Kinetics were measured between 4 and 5 h after the last feed (fasting) and in response to formula feeding using [5-15N]glutamine, [1-13C,15N]leucine, [2H5]phenylalanine, and [15N2]urea tracers. Leucine nitrogen and glutamine kinetics during fasting were significantly higher than those reported in adults. De novo synthesis accounted for ∼85% of glutamine turnover. In response to formula feeding, a significant increase (P = 0.04) in leucine nitrogen turnover was observed, whereas a significant decrease (P = 0.002) in glutamine and urea rate of appearance was seen. The rate of appearance of leucine nitrogen was positively correlated (r2 = 0.59, P = 0.001) with glutamine turnover. Glutamine flux was negatively correlated (r2 = 0.39, P = 0.02) with the rate of urea synthesis. These data suggest that, in the human newborn, glutamine turnover is related to a high anaplerotic flux into the tricarboxylic acid cycle as a consequence of a high rate of protein turnover. The negative relationship between glutamine turnover and the irreversible oxidation of protein (urea synthesis) suggests an important role of glutamine as a nitrogen source for other synthetic processes and accretion of body proteins.

Original languageEnglish (US)
Pages (from-to)E618-E625
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number3 45-3
StatePublished - 2002
Externally publishedYes


  • Appropriate for gestational age
  • Infant of diabetic mother
  • Phenylalanine
  • Small for gestational age
  • Stable isotopes

ASJC Scopus subject areas

  • General Medicine


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