Objectives: Early administration of parenteral amino acids increases whole body nitrogen retention in premature infants. Tracer kinetic studies suggest an increase in whole body protein synthesis as a possible mechanism for this increase in nitrogen retention. However, the effect of early parenteral amino acids on synthesis of specific proteins remains uncertain. Using premature newborn minipigs as a model for human premature newborns, we investigated the effects of parenterally administered amino acids on albumin and skeletal muscle protein fractional synthetic rates.
Methods: Fifteen Yucatan minipigs were delivered by cesarean section 6 days before the mean expected delivery date (day 106 of gestation; expected gestation, 111–113 days) and randomized to two groups immediately after birth: 7 piglets received a mixture of amino acids (0.4 g · kg−1 · h−1) and glucose (0.8 g · kg−1 · h−1) for 5 hours, and 8 piglets (control group) received glucose only. All piglets received a continuous primed infusion of 1-[13C]valine. Arterial plasma free 13C-valine enrichment was measured by gas chromatography/mass spectrometry, and protein synthetic rates were determined by measuring incorporation of 13C-valine into albumin and skeletal muscle protein using gas chromatography/combustion/isotope ratio mass spectrometry.
Results: Administration of amino acids increased albumin (87.0% ± 42.1% [mean ± SD] vs. 37.6% ± 6.8% per 24 hours;P < 0.05) and skeletal muscle fractional synthetic rates (11.60% ± 6.9% vs. 6.5% ± 1.5% per 24 hours;P < 0.05).
Conclusion: We conclude that parenteral amino acids increase albumin and skeletal muscle fractional synthetic rates in premature piglets on the first day of life.
Divisions of *Neonatology and †Pediatric Neurology, Department of Pediatrics, University of Heidelberg, Heidelberg, Germany
Received August 6, 2001; accepted April 17, 2002.
Supported by grant no. He 2195/2-1 from the Deutsche Forschungsgemeinschaft.
Address correspondence and reprint requests to Dr. Gerald Hellstern, Department of Neonatology, Department of Pediatrics, University of Heidelberg, Im Neuenheimer Feld 150 69120, Heidelberg, Germany (e-mail: email@example.com).