Uptake of bilirubin glucuronides by isolated rat hepatocytes

The uptake of bilirubin diglucuronide (BDG) into isolated rat hepatocytes was investigated in order to characterize the mechanism by which bile pigments are transported by the liver. The BDG uptake by hepatocytes was saturable. The uptake was inhibited by bilirubin, sulfobromophthalein, and bilirubin monoglucuronide, but not by taurocholate. The uptake was not affected by replacement of sodium with other cations except for choline. Only when sodium was replaced with choline, was significant decrease in uptake observed. When chloride was replaced with nitrate, BDG uptake decreased, but it was not changed by replacement with sulfate. Metabolic inhibitors did not affect BDG uptake significantly. Thus bile pigments share a common sodium-independent and electrogenic potential-dependent transporter in liver cell membranes. A high concentration of albumin interferes with BDG uptake.