Characteristics of a photoproduct of bilirubin found in vitro and in vivo, and its effect on the bilirubin binding affinity of serum.

The 430 pigment isolated from bilirubin-albumin solutions illuminated in vitro, decreased the bilirubin binding affinity of serum. This effect was demonstrated for both tightly and loosely bound bilirubin in serum, but in albumin solutions pretreated with charcoal only the binding of loosely bound bilirubin was decreased. This finding is of importance because a similar pigment has been isolated from the body fluids of an infant with Crigler-Najjar syndrome. The production and accumulation of 430 pigment during phototherapy might decrease the binding of bilirubin to albumin in the circulation.