Inadequate antioxidant protection in preterm babies: possible cause for hyperbilirubinemia

Many illnesses in pre-term infants are thought to be related to the action of reactive oxygen species and it is conceivable that the oxidants play a certain role in the etiopathogenesis of unconjugated hy- perbilirubinemia. We hypothesized that an important factor in the mechanism of oxidative injury in hyperbilirubinemic infants on the first day of life would be increased oxidative stress in relation to antioxidants. For this aim, 43 pre-term infants as well as full-term healthy reference group (A=50) were subjected in the present study. Additionally, pre-terms were divided in: healthy pre-terms (B=25) and hyperbilirubinemic pre-terms (C=18). Perinatal variables (gestational age, birth weight and Apgar score) were recorded, and erythrocyte superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity and selenium (Se) levels were measured in umbilical cord blood, immediately after the delivery. The obtained results indicate strikingly lower antioxidant capacity of pre-term infants; they showed significantly lower SOD and GPx activity and Se level, compared to the full-term infants (p<0,001, for all). In the hyperbilirubinemic group, GPx activity and Se levels were found to be significantly lower than those in healthy pre-terms (p<0.001, for both), while SOD showed highly increased enzyme activity (p<0.001). Alterations in enzyme activities were accompanied by a simultaneous significant increase in the bilirubin level (p