Amino acid administration directly after birth increases ASR(GSH) in preterm infants. Our data are consistent, however, with higher glutathione concentrations rather than a higher FSR(GSH). Greater availability of glutathione, nevertheless, did not decrease markers of oxidative stress.

Objective Glutathione (GSH) is the main intracellular antioxidant and found in low concentrations in preterm neonates. Fractional synthesis rates of GSH (FSRGSH) in healthy individuals range from 60 – 80 %/day. We speculate that preterm infants have a low FSRGSH compared to healthy individuals, due to low substrate availability and/or slow enzyme development. Methods Preterm infants received a primed continuous infusion of [1‐13C]glycine on postnatal day 2 and 6. In erythrocytes, [1‐13C]glycine incorporated in GSH was determined with a novel method using liquid chromatography – isotope ratio mass spectrometry (IRMS) after 4, 5, and 6 hours of infusion. Erythrocyte free [1‐13C]glycine enrichment was measured with gas chromatography – IRMS as a precursor for GSH. Results On day 2, preterm infants (birth weight 1043 g ± 219 g, gestational age 26 6/7 ± 2 1/7) received glucose solely. On day 6, infants received parenteral and enteral nutrition. FSRGSH in preterm infants increased from 37 ± 4 %/day on day 2 (n=7) to 48 ± 3 %/day on day 6 (n=4) (p=0.002). Conclusion The FSRGSH in preterm infants increases in the first week, but is still much lower than in healthy individuals. Support: Erasmus MC