Proportion of conjugated bilirubin in bile in relation to hepatic bilirubin UDP-glucuronyltransferase activity.

To elucidate the diagnostic relevance of biliary conjugated bilirubin, biliary bilirubin from normal volunteers (NV), patients with Gilbert's syndrome (GS) and Crigler-Najjar syndrome type II (C-N II), and from various rat strains was fractionated. Biliary bilirubin diglucuronide (BDG) was present at lower levels, and bilirubin monoglucuronide (BMG) and unconjugated bilirubin were present at higher levels in GS and C-N II compared with NV, which is consistent with decreased hepatic bilirubin UDP-glucuronyltransferase activity (BGTA). The level of biliary BDG was higher in Wistar-Kyoto rats and lower in heterozygous (Jj) Gunn rats than in SD and Wistar rats. The hepatic BGTA level in heterozygous (Jj) Gunn rats was decreased to 60% of that in Wistar rats, in accordance with decreased biliary BDG. On the other hand, BGTA in Wistar-Kyoto rats whose biliary BDG level was high, was not different from that of Wistar and SD rats. Thus, a correlation between BGTA and biliary bilirubin fractions may not exist on some occasions.