Hepatic intracellular distribution of tritium-labeled unconjugated and conjugated bilirubin in normal and Gunn rats.

Relatively little is known about the mechanism, regulation, or subcellular localization of the hepatic uptake, storage, conjugation, and excretion of bilirubin. In the work here reported, the ultra- structural localization of the sites of these proc- esses was studied by determining the subcellular distribution and chemical nature of bilirubin after the injection of physiologic amounts of tritium- labeled unconjugated bilirubin (UCB-3H) and conjugated bilirubin (CB-3H) in normal and glucuronyl transferase-deficient (Gunn) rats (1, 2). Studies were also performed using bilirubin- 14C for comparison with the intracellular distri- bution of tritiated bilirubin. While these studies were in progress, Brown, Grodsky, and Carbone (3) described the subcellular distribution of in- jected UCB-3H in normal rat liver.