Direct-Reacting Bilirubin, Bilirubin Glucuronide, in Serum, Bile and Urine

摘要

The van den Bergh reaction is one of the most widely used clinical tests. An explanation for the "direct" and "indirect" types of reaction has long been a subject of investigation. A time-honored explanation for the indirect reaction has been that some of the bilirubin in serum is conjugated with protein and requires treatment with alcohol before the characteristic reaction with a diazo compound. The present report describes a series of experiments in which it was demonstrated that that portion of the bilirubin which gives the direct van den Bergh reaction is conjugated with glucuronic acid. This is a water-soluble compound. Free bilirubin, not conjugated with glucuronic acid, is insoluble in water and requires prior addition of alcohol to initiate the coupling with the diazo reagent. The free bilirubin is an indirect-reacting form of bilirubin. The kidneys can excrete only the water-soluble conjugated form of bilirubin. The existing interpretations of the van den Bergh reaction are not altered by this finding. Conjugation of bilirubin is with glucuronic acid rather than protein as formerly believed.