Ontogeny of cationic amino acid transport systems in rat placenta

acid transport systems in rat placenta. Am. J. PhysioZ. 267 (Cell Physiol. 36): C804-C811, 1994.-Gestational regulation of the placental transfer of amino acids from maternal to fetal circulations is essential for the proper development of the fetus. The cationic amino acid transport systems of the microvillous (maternal facing) and basal (fetal facing) mem-branes of the rat placental syncytiotrophoblast were exam-ined. Inhibition analysis documented the presence of three kinetically distinct cationic amino acid transport mechanisms: a single Na+-dependent mechanism in the microvillous mem-brane, which increased in activity from 14 to 20 days gestation but was absent from the basal membrane throughout the entire gestational period (system Bo>+), and two Na+-indepen-dent transport systems in both membrane domains, one that is completely inhibited by leucine, which increased in activity i