INTESTINAL ABSORPTION OF BILE PIGMENTS. I. THE ENTEROHEPATIC CIRCULATION OF BILIRUBIN IN THE RAT*

Abstract

The absorption of bilirubin from the intestine was measured, utilizing unconjugated and conjugated bilirubin-C14, in rats prepared with an external biliary fistula. After intraduodenal instillation of each pigment, from 4 to 40 per cent of the administered radioactivity was re-excreted in the bile, while less than 2 per cent appeared in the urine. It was established in experiments on similarly prepared Gunn rats (deficient in hepatic glucuronyl transferase) that the unconjugated pigment was readily absorbed intact from both the small and large bowel. In contrast, conjugated bilirubin-C14 was not appreciably absorbed unless first hydrolyzed to the unconjugated form.