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Urea production and recycling in neonates
R A Wheeler1, A A Jackson, D M Griffiths
1Wessex Regional Centre for Paediatric Surgery, Southampton General Hospital, England.
Journal of Pediatric Surgery
|May 1, 1991
Summary
Newborn infants utilize urea nitrogen from breast milk. Most urea produced is broken down in the colon, making its nitrogen available for metabolism, not just excreted in urine.
Area of Science:
- Neonatal nutrition
- Metabolic research
- Gastroenterology
Background:
- Urea constitutes a significant portion (15%) of nitrogen in breast milk.
- The functional role of urea in neonatal nutrition remains largely undetermined.
- Previous research has not quantified urea kinetics in newborn infants.
Purpose of the Study:
- To conduct the first measurements of urea kinetics in full-term newborn infants.
- To investigate the potential utilization of urea as a nitrogen source in neonates.
- To determine the fate of urea produced by newborns.
Main Methods:
- Six newborn infants received a continuous 24-hour nasogastric infusion of 15N15N-urea.
- Urine samples were collected every 2 hours for isotopic enrichment analysis via mass spectrometry.
- Urea kinetics were calculated using the Jackson method.
Main Results:
- The average urea production rate was 17.3 mmol/kg/d.
- Urinary urea excretion averaged 3.5 mmol/kg/d, representing only 20% of the production rate.
- Approximately 80% of produced urea was hydrolyzed in the colon, with nitrogen salvaged for metabolism.
Conclusions:
- Urinary urea excretion is an unreliable indicator of urea production in newborns.
- Newborns exhibit substantial salvaging of urea nitrogen by the colon.
- Urea serves as a significant source of metabolically available nitrogen for neonates.