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

In man, sulfaphenazole has a lower affinity for the albumin of 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 su1faphenazole for fetal and neonatal albumin compared to that for adult albumin probably is the result of the presence of a tightly bound endogenous ligand, such as bilirubin, on fetal and neonatal albumin.