POSTNATAL MATURATION OF THE BLOOD-BRAIN-BARRIER FOR UNBOUND BILIRUBININ NEWBORN PIGLETS

The postnatal maturation of the blood-brain barrier (BBB) for unbound bilirubin was studied in 2-day- and 2-week-old piglets. Hyperbilirubin emia was induced by bolus infusion of bilirubin at 25 mg/kg followed b y continuous infusion of 20 mg/kg/h for 3 h. During the study period, arterial blood pH and blood gas tensions, serum osmolarity, and mean a rterial blood pressures were within the physiologic range. Brain bilir ubin content and the brain/blood distribution ratio for bilirubin were higher in the 2-day-old than in the 2-week-old piglets. In both age g roups, regional brain bilirubin concentration and brain/blood ratios w ere higher in subcortical regions (cerebellum and brainstem) than in t he cerebral cortex. We conclude that in newborn piglets the blood-brai n barrier for unbound bilirubin matures with increasing postnatal age and that irrespective of maturity the relative permeability of the BBB for bilirubin appears higher in subcortical than in cortical regions.