INFLUENCE OF BILIRUBIN ON THE ANTIOXIDANT CAPACITY OF PLASMA IN NEWBORN-INFANTS

In vitro, bilirubin is a strong antioxidant, but in vivo its capacity to act as a scavenger of toxic oxygen radicals remains poorly document ed. The aim of this study was to evaluate if bilirubin had antioxidant properties in jaundiced infants. The antioxidant capacity of neonatal plasma was measured in Trolox equivalents (TEAC, mmol/l) and correlat ed in vitro with plasma bilirubin concentrations (r(2) = 0.99). Plasma TEAC was compared before and after exchange transfusions for neonatal hyperbilirubinemia (250-435 mu mol/l). The antioxidant properties of the paired blood samples before and after exchange transfusions(TEAC: 1.67 +/- 0.12 vs. 1.37 +/- 0.09 mmol/l, n = 11) varied in proportion t o the serum bilirubin levels. The changes in other antioxidants were n ot large enough to account for the magnitude of change in antioxidant capacity. Therefore, in vivo, the plasma antioxidant capacity of jaund iced newborn infants is related to the level of bilirubin.