Neutral amino acid transport in placental plasma membrane vesicles in the late pregnant rat. Evidence for a B0-like transport system.
Rat placental plasma membrane vesicles have been used to study both alanine and leucine transport at late gestation. The results presented are consistent with the presence of more than two separate transport systems for neutral amino acids in the rat placenta. One system is clearly Na(+)-independent and transports alanine (KM approximately or = 2 mM; Vmax approximately or = 360 pmol ala/mg prot x 5 s), leucine (KM approximately or = 0.07 mM; Vmax approximately or = 100 pmol leu/mg prot x 5 s), serine, cysteine and 2-amino-2 norbornane carboxylic acid (BCH) showing similar properties to the L system, present in many cell types. The other systems are Na(+)-dependent and transport alanine (a, KM approximately or = 5 mM; Vmax approximately or = 3761 pmol ala/mg prot x 5 s; b, KM approximately or = 0.07 mM; Vmax approximately or = 376 pmol ala/mg prot x 5 s), cysteine, serine and leucine (KM approximately or = 0.2 mM; Vmax approximately or = 112 pmol leu/mg prot x 5 s) with different kinetic behaviour referring affinity and capacity. While one of them is sensitive to inhibition by methylaminoisobutyric acid (MeAIB), the other is a B0-like system similar to that characterized in bovine brush-border enterocyte membrane vesicles.
Carbó
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Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Spain.
López-Soriano
F J
FJ
Argilés
J M
JM
D000409:Alanine / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism; D026905:Amino Acid Transport Systems; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D012964:Sodium; D000469:Alkaline Phosphatase; D007930:Leucine; D000409:Alanine