Xylose, glucose, and glucuronic acid conjugation of bilirubin in the newborn rat.

The development and relative contribution of hepatic bilirubin conjugation with glucuronic acid, xylose, and glucose was studied in vitro in newborn rats 1-20 days old. In adult control rats, 75% of the conjugates formed were with glucuronic acid, whereas in 1-day-old newborns, only 50% of the conjugates were with glucuronic acid (P less than 0.02) while xylose and glucose conjugates of bilirubin together were equal to that of glucuronic acid. By day 4, total conjugating capacity increased to adult levels and a mature pattern of distribution. In response to phenobarbital treatment, xylose and glucose conjugation increased 4 days earlier than glucuronide conjugation and maximal induction occurred 8 days sooner for nonglucuronide conjugation than for glucuronide.