RESUMO
BACKGROUND: The availability of glutathione, the main intracellular antioxidant, is compromised in preterm neonates. A possible explanation is the low availability of substrate for synthesis, because many neonatologists are reluctant to administer amino acids in the direct postnatal period for fear of intolerance. OBJECTIVE: The objective of the study was to determine the effects of amino acid administration directly after birth on glutathione synthesis rates and markers of oxidative stress. DESIGN: Premature infants (<1500 g) received from birth onward either dextrose (control group; n = 10) or dextrose plus 2.4 g amino acids . kg (- 1) . d(-1) (intervention group; n = 10). On postnatal day 2, [1-(13)C]glycine was administered to determine glutathione fractional synthesis rates (FSR(GSH)) and absolute synthesis rates (ASR(GSH)) in erythrocytes. In plasma, advanced oxidized protein products and dityrosine, both markers of oxidative stress, were measured. The results are expressed as means +/- SDs. RESULTS: The FSR(GSH) was not different between groups: 44 +/- 6 and 48 +/- 9%/d in the control and intervention groups, respectively (P = 0.28). The concentration of erythrocyte glutathione was higher (P < 0.001) in the intervention group (2.28 +/- 0.35 mmol/L) than in the control group (1.73 +/- 0.37 mmol/L). ASR(GSH) values were 6.5 +/- 1.5 and 11.3 +/- 1.9 mg . kg(-1) . d(-1) in the control and intervention groups, respectively (P < 0.001). Advanced oxidized protein products and dityrosine concentrations were not significantly different between groups. CONCLUSIONS: 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.
