Intrauterine growth restriction induces up-regulation of cerebral aromaticamino acid decarboxylase activity in newborn piglets: [F-18]fluorodopa positron emission tomographic study

There is evidence that intrauterine growth restriction (IUGR) is associated with altered dopaminergic function in the immature brain. However, the rel evant enzyme activities have not been measured in the living neonatal brain together with brain oxidative metabolism. Therefore, fluorine-18-labeled 6 -fluoro-L-3.4dihydroxyphenylalanine (FDOPA) was used together with positron emission tomography to estimate the activity of the aromatic amino acid de carboxylase in the brain of 10 newborn IUGR piglets (2 to 5 d old; body wei ght, 908 +/- 109 g) and in 10 normal-weight (3 to 5 d old; body weight, 214 2 +/- 373 g) newborn piglets. The regional transport of FDOPA to the brain and the clearance rate of labeled metabolites from brain tissue were broadl y similar in the two groups. However, the regional rate constant for back f lux from the brain was markedly increased in IUGR piglets for striatum (72% ) and frontal cortex (83%) (p < 0.05). Furthermore, the rate constant for c onversion of FDOPA to tluorodopamine was markedly increased (between 48% in cerebellum and 91% in mesencephalon, p < 0.05) in all brain regions of IUG R piglets studied. Thus, it is suggested that IUGR induces an up-regulation of aromatic amino acid decarboxylase activity that is not related to alter ations in brain oxidative metabolism.