Glucuronide synthesis in foetal liver and other tissues

Abstract

Low o-aminophenyl glucuronide synthesis in fetal liver of guinea pig and man and in neonatal mouse liver has been shown to be due to low levels of uridine diphosphate glucuronic acid and of uridine diphosphate-transglucuronylase (glucuronyl transferase) activity, the enzyme itself probably being present only in small amount. In early fetal guinea-pig liver both these levels are negligible, but increase towards full term. Relatively greater conjugation was observed in homogenates fortified with uridine diphosphate glucuronic acid than in corresponding slices; the bearing of this phenomenon on formation of the nucleotide and on fatty infiltration of fetal liver is discussed. After birth, guinea-pig liver rapidly assumes the glucuronide-synthesizing capacity of the adult. A somewhat similar pattern is described for the infant mouse. Synthesis below adult levels also of ( - )-menthyl glucuronide and of the ester-linked p-aminobenzoyl glucuronide occurs in homogenates of fetal guinea-pig liver, o-Aminophenyl glucuronide synthesis in early fetal kidney is negligible but increases towards full term, being at birth, when fortified with glucose, higher than in corresponding liver slices, though still below adult level. The most active site of glucuronide synthesis so far examined in the early fetus of the guinea pig is the stomach. "Defective" glucuronide formation in liver and kidney appears to be a fetal characteristic of the species studied, and its relation to bilirubin conjugation in neonatal jaundice is discussed.