[Inhibition of L-tyrosine transport in isolated synaptosomes from rat brain in the presence of L-tryptophan and L-phenylalanine].

The high-affinity transport system of L-tyrosine into rat brain synaptosomes is competitively inhibited by L-Tryptophan and by L-Phenylalanine. These results support the common carrier hypothesis for the transport of aromatic amino acids into the neuron and suggest that the high levels of phenylalanine present in phenylketonuria could be responsible for the impairment synthesis of neurotransmitter monoamines found in brain of patients affected by that disease.