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Oxidant stress responses in premature infants during exposure to hyperoxia
C V Smith1, T N Hansen, N E Martin
1Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030.
Insights
Newborn infants show significant oxidant stress, indicated by high glutathione disulfide (GSSG) and low glutathione (GSH) levels. These responses occur even with room air, suggesting lung involvement in premature infants.
Area of Science:
- Neonatal Medicine
- Biochemistry
- Oxidative Stress Research
Background:
- Premature infants are susceptible to oxidative stress.
- Understanding oxidant stress markers is crucial for neonatal care.
Purpose of the Study:
- To evaluate oxidant stress responses in newborn infants using glutathione (GSH) and glutathione disulfide (GSSG) levels.
- To investigate the relationship between oxygen exposure and these markers.
Main Methods:
- Measured plasma GSH and GSSG concentrations in mechanically ventilated newborn infants (23-42 wk gestational age).
- Collected blood samples on days 1, 3, 5, and weekly thereafter.
- Analyzed arterial and venous blood samples for GSH and GSSG levels.
Main Results:
- Plasma GSSG concentrations were significantly higher (order of magnitude) in infants compared to adults.
- Plasma GSSG inversely correlated with inspired oxygen tension, linked to gestational age.
- Plasma GSH concentrations were substantially lower in premature infants than in adults.
- Arterial GSSG was higher than venous GSSG, while arterial GSH was lower than venous GSH, suggesting lung production of GSSG.
Conclusions:
- Elevated GSSG and low GSH indicate marked oxidant stress in prematurely born infants, even on room air.
- Positive arteriovenous GSSG gradients suggest the lung as a source of increased GSSG in these infants.
Abstract:
To assess oxidant stress responses in newborn infants treated with elevated concentrations of oxygen, we measured plasma concentrations of glutathione (GSH) and glutathione disulfide (GSSG) in newborn infants ranging from 23 to 42 wk gestational age. All infants recruited into the study were mechanically ventilated and had catheters placed in their umbilical arteries as part of their normal clinical management. Blood samples were obtained on d 1, 3, and 5 and weekly thereafter or until the catheters were removed. We observed plasma concentrations of GSSG in these infants that were frequently an order of magnitude higher than the 0.1 to 0.3 microM we find in adults. Interestingly, plasma GSSG concentrations were inversely correlated to the inspired oxygen tensions. This effect appeared to arise from the patient selection criteria whereby, of the infants studied, those breathing the lowest partial pressures of oxygen were the smallest and gestationally youngest. A second observation was that plasma concentrations of GSH in the premature infants were substantially, indeed often dramatically, lower than we have observed in adult humans (6 to 10 microM). Finally, we found that in patients with both umbilical arterial and umbilical venous catheters arterial GSSG concentrations were consistently higher than venous concentrations; conversely, arterial GSH concentrations were lower than venous concentrations. The elevated GSSG concentrations we observed in these infants indicate marked oxidant stress responses in prematurely born infants, even in those infants exposed only to room air. The positive arteriovenous gradients of GSSG concentrations across the lungs of these infants suggest that at least some of the increased plasma GSSG originates in the lung.(ABSTRACT TRUNCATED AT 250 WORDS)