The binding of sulfaphenazole to fetal, neonatal, and adult human plasma albumin

In man, sul f aphenazole has a lower affinity for the albumin o f the fetus and neonate than for that of the adult. Removal of bound endogenous anions from neonatal albumin by treatment with charcoal at pH 3.0 restored the affinity of the protein for sulfaphenazole to the adult level. Prior treatment of adult albumin with bilirubin reduced the affinity of the protein for sulfaphenazole to that observed in fetal and neonatal albumins. Thus the reduced affinity of sulfaphenazole for fetal and neonatal albumin compared to that for adult albumin probably is the result o f the presence o f a tightly bound endogenous ligand, such as bilirubin, on fetal and neonatal albumin.