Placental Amino Acids Transport in Intrauterine Growth Restriction

Figure 1

Mechanisms of amino acid transport. Na⁺-dependent transporters (T) permit the uptake of amino acids (aa) into the cell; amino acids are actively transported against a concentration gradient, using a Na⁺ gradient maintained by the Na⁺/K⁺ ATPasi. Amino acid exchangers (Ex) mediate the passage of amino acids by switching the position of one amino acid (aa1) from outside the cell and with one other (aa2) inside the cell. The transport across the basal membrane is poorly understood: may be mediate by amino acid exchangers (swapping one amino acid within the syncytiotrophoblast for one in the fetal capillary) or a nonexchanger passage may exist () such as facilitate diffusion. (electron microscopy image: courtesy of GP Bulfamante; Diagram of amino acids transport modified from [15]).