Maternal hyperphenylalaninemia induced experimentally: decreased incorporation of 14C-leucine into protein in the brain of the fetus.

Abstract

14C-leucine was intraperitoneally injected to pregnant rats with experimental hyperphenylal-aninemia. One hour following the 14C-leucine injection the radioactivities of amino acid fraction and protein fraction of the brain and liver were measured both in maternal and in fetal rats. Little inhibitory effect of an excess of phenylalanine was observed on the uptake of 14C-leucine by the liver or on its incorporation into the liver protein in the maternal rats. The striking inhibition of the uptake and incorporation of 14C-leucine was found in the brain of fetuses from the phenyl-alanine-loaded rats, in contrast with those of controls (p<0.001). In the fetal liver and maternal brain a similar inhibitory effect was also noted (p<0.05). These findings suggest that an excess of phenylalanine in maternal blood transfers across the placenta into the fetus, concentrates in fetal blood, and interferes with protein synthesis in fetal organs, particularly in the brain. These mechanisms may play an important role on the development of mental retardation and microcephaly of fetus in maternal PKU.