Fetomaternal placental transfer mechanisms of aromatic amino acids in Macaca mulatta

We investigated aromatic amino acid transfer mechanisms from fetus to mother in third-trimester pregnancies in rhesus monkeys after the administration of radioactive phenylalanine to the fetal circulation. The results indicated that fetomaternal transfer takes place mainly by facilitated diffusion via specific membrane carriers. This mechanism might participate in regulating amino acid concentrations in the fetus.