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The effect of hematin on bilirubin binding in bilirubin-enriched neonatal cord serum
Insights
Hematin in infant serum can affect bilirubin binding to albumin, potentially increasing the risk of kernicterus. However, the concentrations found in ABO hemolytic disease are unlikely to be physiologically significant.
Area of Science:
- Neonatal medicine
- Biochemistry
- Hematology
Background:
- ABO hemolytic disease in infants can lead to kernicterus.
- Serum hematin has been hypothesized to interfere with bilirubin-albumin binding.
Purpose of the Study:
- To investigate the effect of hematin on bilirubin binding to albumin in neonatal serum.
- To determine the physiological relevance of hematin in ABO hemolytic disease.
Main Methods:
- Horseradish peroxidase assay used to measure bilirubin binding.
- Cord serum from healthy infants was enriched with bilirubin and varying hematin concentrations.
Main Results:
- Hematin significantly impaired bilirubin binding at half to equimolar ratios with bilirubin.
- Serum from infants with ABO hemolytic disease did not contain high hematin concentrations.
- No difference observed between dilute and undilute peroxidase assays.
Conclusions:
- Hematin can alter bilirubin binding in neonatal serum.
- Hematin is unlikely to be of physiological importance in ABO-isoimmune hemolysis.
Abstract:
It has been suggested that the serum of infants with ABO hemolytic disease contains hematin which might interfere with bilirubin binding to albumin, increasing the risk of kerincterus. Using the horseradish peroxidase assay, we investigated this possibility. Cord serum from healthy term infants was enriched with bilirubin to a bilirubin/albumin molar ratio of 0.6, and then varying amounts of hematin were added. Hematin had a significant adverse effect on bilirubin binding when present in half to equimolar ratios with bilirubin. This high concentration of hematin does not appear to be present in serum from infants with ABO hemolytic disease and no difference was seen when comparing the dilute and the undilute peroxidase assays. These data suggest that hematin can alter bilirubin binding in neonatal serum but is not os physiologic importance for infants with ABO-isoimmune hemolysis.