CERTAIN ASPECTS OF TYROSINE METABOLISM IN THE YOUNG. II. THE TYROSINE OXIDIZING SYSTEM OF FETAL RAT LIVER 12

Abstract

The activity of the tyrosine oxidizing system in fetal rat liver is 1/12 to 1/15 as great as in newborn or adult rat liver. This low activity can be partially explained by a lack of tyrosine transaminase activity in the presence of excess [alpha]-ketoglutarate and pyridoxal phosphate. At birth the over-all tyrosine oxidizing activity of the liver is at the adult level. If the infant rats are fed, the tyrosine oxidizing activity of the liver drops in 5 hours to 1/2 the activity of the liver of the adult or the newborn rat. If the rats are fasted for 5 hours after birth, the tyrosine oxidizing activity of the liver remains at the same level as in the newborn rat.