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The Mechanism of Human Placental Urea Transport: A Study Using Placental Brush Border (Microvillous) Membrane Vesicles
Author(s) -
Hisanaga Hiroyasu,
Iioka Hideaki,
Moriyama Ikuko,
Nabuchi Kaoru,
Morimoto Keiko,
Ichijo Motohiko
Publication year - 1991
Publication title -
asia‐oceania journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 50
eISSN - 1447-0756
pISSN - 0389-2328
DOI - 10.1111/j.1447-0756.1991.tb00253.x
Subject(s) - brush border , urea , vesicle , chemistry , membrane , ionophore , biophysics , membrane transport , biochemistry , kinetics , electrochemical gradient , chromatography , biology , physics , quantum mechanics
To elucidate the mechanism of placental amino acid transport, the transport of amino acids into brush border membrane vesicles was investigated using brush border membrane vesicles (BBMV) separated from the human full‐term placenta.1 The transport of l ‐alanine and l ‐glutamine into the brush border membrane vesicles prepared from either early gestational placenta or full‐termed placenta disclosed a typical overshooting phenomenon in the presence of H + concentration gradient (extravesicular pH > intravesicular pH). 2 The H + ‐dependent overshooting transport of urea into the brush border membrane vesicles disappeared in the presence of H + ionophore. 3 The initial velocity of H + concentration gradient dependent uptake of urea into the brush border membrane vesicles was regulated by the saturation kinetics determined by the concentration of urea. The values of K m and V max , calculated as the kinetic parameters of urea transport by reciprocal plotting of the initial velocity of uptake and the concentration of urea, were 10.8 mM and 410 μmol/mg protein/10 sec, respectively.The above results indicate that a transport system which transports urea in exchange for H + exists in human full‐term placental microvillous membrane.