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How phototherapy affects the relation between serum bilirubin and plasma malondialdehyde in neonates
  1. Department of Biochemistry
  2. Faculty of Medicine
  3. Dokuz Eylül University
  4. Inciralti, Izmir, Turkey
  5. Department of Paediatrics
  6. Dokuz Eylül University

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Editor—The study by Yigit et al 1 showed that serum malondialdehyde (MDA) concentrations were higher in infants with hyperbilirubinaemia than in controls, but there was no significant correlation between serum MDA and bilirubin concentrations in jaundiced neonates without haemolysis.

The results of our study confirmed those of Yigitet al, but we also investigated whether treating neonates with phototherapy increases the risk of oxygen free radical injury. We evaluated plasma MDA which is an index of free radical induced lipid peroxidation, and serum bilirubin concentrations, in blood samples taken from healthy, term neonates with non-haemolytic hyperbilirubinaemia (n=19, total bilirubin > 15.0 mg/dl) before and after phototherapy. These were compared with those taken from healthy neonates without hyperbilirubinaemia (n=22, total bilirubin < 10.0 mg/dl). The mean birthweight, gestational age, and postnatal age did not differ between the study and control groups (p > 0.05). All babies were fed their mothers' milk. MDA concentrations were determined using the modified method of Stocks and Dormandy2 with the thiobarbituric acid (TBA) test.

Plasma MDA concentrations in neonates with jaundice (0.99 (SEM 0.15) nmol/ml) were significantly higher than those of the healthy infants (0.89 (0.16) nmol/ml) (p=0.038). There was a significant difference between the MDA concentrations of the study group before and after phototherapy (0.99 (0.15) vs 0.85 (0.20) nmol/ml; p=0.0016). However, no significant correlation was found between plasma MDA and serum bilirubin concentrations before and after phototherapy (r=0.16, p > 0.05;r=0.09, p > 0.05).

Bilirubin is an important free radical scavenger in early neonatal life in response to oxidative stress. Phototherapy reduces the concentrations of circulating bilirubin, but there are conflicting data on red cell membrane lipid peroxidation secondary to phototherapy.3 ,4 Our data suggest that phototherapy does not induce lipid peroxidation in healthy term infants with non-haemolytic hyperbilirubinemia.