These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: [Studies on the amino acid transport systems in the human placenta--L-alanine and L-leucine uptake by microvillous brush border membrane vesicles].
    Author: Asai M.
    Journal: Nihon Sanka Fujinka Gakkai Zasshi; 1983 Jan; 35(1):10-8. PubMed ID: 6298324.
    Abstract:
    To characterize the placental amino acid transport systems, L-alanine and L-leucine uptakes were studied using microvillous brush border membrane vesicles prepared from human placenta. The specific activities of alkaline phosphatase and 5'-nucleotidase in the membrane preparation were enriched 9-11 times as high as those in the homogenate. Intravesicular water (IVW) volume determined with 3-O-methyl-D-glucose was 0.59 microliters/mg protein. The saturation kinetics of L-leucine uptake by the vesicles equilibrated with Na+ gave a single set of Km (4.2mM) and Vmax (1.16 mumol/ml IVW/30s). These parameters were clearly different from those for L-alanine uptake reported previously (Asai et al.: Biochem. Int., 4:377, 1982). In the presence of an inward Na+-gradient L-leucine uptake was stimulated about 2 times, but transient accumulation was not observed differing from L-alanine uptake. Discrimination of the neutral amino acid transport systems in the presence of an inward 100mM Na+-gradient revealed that the relative contributions of A, ASC and L systems, and simple diffusion were 55, 20, 15 and 10% for L-alanine, and 45, 0, 15 and 40% for L-leucine, respectively. The results indicate that the neutral amino acid transport systems in the human placental microvillous membranes are clearly different between L-alanine and L-leucine.
    [Abstract] [Full Text] [Related] [New Search]