Reduced levels of uridine diphosphate glucose pyrophosphorylase activity in fetal and neonatal human and guinea pig liver.

Uridine diphosphate glucose pyrophosphorylase (UDPGPP) is the first enzyme in the bilirubin conjugation pathway. A study aiming to screen for red blood cell UDPGPP deficiency in newborns with hyperbilirubinemia was carried out. No individuals with severe UDPGPP deficiency were found, however, levels of UDPGPP in premature and at term newborns were lower than in adults. These findings led to the study of UDPGPP in human fetal, neonatal and adult liver, using guinea pig tissues as a parallel control. UDPGPP activities in fetal and neonatal samples were also significantly lower than in adult ones in both species. Therefore, it is postulated that the reduced levels of UDPGPP in fetal and neonatal liver could be a factor which contributes to the pathogenesis of the physiologic jaundice in human newborns.