Characterization of amino acid transport systems in human placental basal membrane vesicles

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) membranes of the rat placental syncytiotrophoblast were examined. Inhibition analysis documented the presence of three kinetically distinct cationic amino acid transport mechanisms: a single Na(+)-dependent mechanism in the microvillous membrane, 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(+)-independent transport systems in both membrane domains, one that is completely inhibited by leucine, which increased in activity in both the microvillous and basal membrane domains, and the other that is leucine insensitive, which remained fairly constant in the basal membrane and increased throughout gestation in the microvillous membrane (system y1+). Northern analysis with the system y1+ cDNA revealed a specific band of approximately 7.4-7.9 kb, which increased with increasing gestational age.

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AMINO ACID TRANSPORT SYSTEMS IN BRUSH-BORDER MEMBRANE VESICLES FROM LEPIDOPTERAN ENTEROCYTES

Journal of Experimental Biology ◽

10.1242/jeb.143.1.87 ◽

1989 ◽

Vol 143 (1) ◽

pp. 87-100

Author(s):

GIORGIO M. HANOZET ◽

BARBARA GIORDANA ◽

V. FRANCA SACCHI ◽

PAOLO PARENTI

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Glutamic Acid ◽

Brush Border ◽

Amino Acid Transport ◽

Brush Border Membrane ◽

Membrane Vesicles ◽

Transport Systems ◽

Acid Transport ◽

Luminal Membrane

The presence of different potassium-dependent amino acid transport systems in the luminal membrane of the larval midgut of Philosamia cynthia Drury (Saturnidae, Lepidoptera) was investigated by means of countertransport experiments performed with brush-border membrane vesicles. The vesicles were preloaded with 14 different unlabelled amino acids, whose ability to elicit an intravesicular accumulation over the equilibrium value of six labelled amino acids (L-alanine, L-leucine, L-phenylalanine, L-glutamic acid, L-lysine and L-histidine) was tested. For histidine, the results were compared with those obtained from inhibition experiments, in which the same 14 amino acids were used as inhibitors on the cis side of the brush-border membrane. The data demonstrate the presence in the lepidopteran luminal membrane of distinct transport pathways for lysine and glutamic acid. The transport of most neutral amino acids, with the exclusionof glycine and proline, seems to occur through a system that may be similar to the neutral brush-border system (NBB) found in mammalian intestinal membranes. This system is also able to handle histidine.

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Effects of acetaldehyde and/or ethanol on neutral amino acid transport systems in microvillous brush border membrane vesicles prepared from human placenta

Cellular and Molecular Life Sciences ◽

10.1007/bf01964810 ◽

1985 ◽

Vol 41 (12) ◽

pp. 1566-1568 ◽

Cited By ~ 8

Author(s):

M. Asai ◽

O. Narita ◽

S. Kashiwamata

Keyword(s):

Amino Acid ◽

Human Placenta ◽

Brush Border ◽

Amino Acid Transport ◽

Brush Border Membrane ◽

Membrane Vesicles ◽

Brush Border Membrane Vesicles ◽

Neutral Amino Acid ◽

Transport Systems ◽

Acid Transport

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Brush-border amino acid transport mechanisms in carnivorous eel intestine

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.257.3.r506 ◽

1989 ◽

Vol 257 (3) ◽

pp. R506-R510 ◽

Cited By ~ 1

Author(s):

C. Storelli ◽

S. Vilella ◽

M. P. Romano ◽

M. Maffia ◽

G. Cassano

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Brush Border ◽

Amino Acid Transport ◽

Membrane Vesicles ◽

Anguilla Anguilla ◽

Neutral Amino Acid ◽

Transport Systems ◽

European Eel ◽

Acid Transport

Brush-border membrane vesicles (BBMV) were prepared from European eel (Anguilla anguilla) intestinal epithelium by a magnesium-ethylene glycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) precipitation technique. Amino acid transport by these purified vesicle preparations was investigated using either radiolabeled substrates or the voltage-sensitive fluorescent dye 3,3'-diethylthiadicarbocyanine iodide [DiSC2(5)]. All amino acids tested exhibited carrier-mediated, Na+-dependent and Na+-independent transfer processes plus diffusion. The only exceptions were glutamic acid and proline, which displayed Na+ dependency and diffusion but did not appear to be transported by Na+-independent agencies. Carrier-mediated transport kinetic constants (Kapp and Jmax) for several amino acids are reported. Cis-inhibition experiments suggested the presence of at least four distinct Na+-dependent transport systems in eel intestinal BBMV: 1) an anionic transport process for glutamic and aspartic acids; 2) a cationic mechanism for lysine and arginine; 3) a relatively specific neutral amino acid carrier for proline and alpha-(methylamino)isobutyric acid; and 4) a nonspecific neutral amino acid system for most other substrates of this group. This scheme for carnivorous fish intestine most closely approximates that reported for mammalian gut with minor dissimilarities that may relate to metabolic differences or specific dietary requirements of the two vertebrate groups.

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