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  • Title: [Studies on L-glutamate transport mechanism in human placental trophoblast microvilli membrane vesicles].
    Author: Iioka H, Moriyama I, Kyuma M, Ito K, Amasaki M, Ichijo M.
    Journal: Nihon Sanka Fujinka Gakkai Zasshi; 1985 Feb; 37(2):207-12. PubMed ID: 3973444.
    Abstract:
    The uptake of L-glutamate in brush border (microvilli) vesicles prepared from human term placenta was studied using the rapid filtration technique. The uptake of L-glutamate into the vesicles occurred osmotically, and preincubation with L-glutamate increased the uptake of amino acid. These findings indicate that the uptake of L-glutamate by placental trophoblast brush border membranes represents the transport into membrane vesicles. A Na+ electrochemical gradient (extravesicular greater than intravesicular) stimulated the initial rate of L-glutamate uptake about three times. The initial rate of transport exhibited saturation kinetics with respect to the L-glutamate concentration; an apparent Km of 0.15 mM and V max of 70 pmol/mg protein in 20 seconds were calculated. The uptake of L-glutamate into the vesicles was competitively inhibited by L-glutamate and L-cysteate (acidic amino acid). These results indicate that a Na-dependent acidic amino acid specific transport system exists in the placental trophoblast microvilli membrane. These results indicate that the transport of L-glutamate across the placental microvilli membrane is sodium-dependent and carrier mediated.
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