IN the voluminous literature on bile-pigment metabolism¹ little attention has been given to the possibility that bilirubin is reabsorbed from the intestinal tract. Recent studies utilizing G¹⁴-labeled pigment² have demonstrated that unconjugated bilirubin is absorbed rapidly from the intestine of rats. In contrast conjugate is not absorbed intact,² hepatic conjugation creating a barrier against the reabsorption of the potentially toxic³ unconjugated pigment. In rats this conjugate barrier is incomplete; a fraction of the administered bilirubin glucuronide is hydrolyzed in the intestine, and significant quantities of the released unconjugated bilirubin are absorbed.

The following studies were performed to determine whether . . .