scholarly journals The transport of glutamine and alanine into rat colonocytes

1986 ◽  
Vol 238 (1) ◽  
pp. 131-135 ◽  
Author(s):  
M S M Ardawi
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Metabolic Function ◽  
Carrier System ◽  
System A ◽  
Alanine Transport ◽  
Common Carrier ◽  
Isolated Rat

The transport of glutamine and alanine into isolated rat colonocytes was studied. The transport of both amino acids appears to be dependent on a Na+ gradient. The apparent Km values for the transport of glutamine and alanine were 2.56 +/- 0.84 and 5.35 +/- 1.20 mM respectively, but with similar Vmax. values. Glutamine and alanine transport were mutually competitive, and the transport of both amino acids was competitively inhibited by 2-methylaminoisobutyrate. In contrast, histidine inhibited the transport of both glutamine and alanine non-competitively. It is concluded that glutamine and alanine are transported into rat colonocytes by a common carrier system similar to System A of other cells. It is suggested that the metabolic function of this transport system in rat colonocytes might be the partial exchange of extracellular glutamine for intracellular alanine.

scholarly journals Expression and adaptive regulation of amino acid transport system A in a placental cell line under amino acid restriction

Reproduction ◽  
2006 ◽  
Vol 131 (5) ◽  
pp. 951-960 ◽  
Author(s):  
H N Jones ◽  
C J Ashworth ◽  
K R Page ◽  
H J McArdle
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Line ◽  
Transport System ◽  
Amino Acid Transport ◽  
Essential Amino Acids ◽  
Acid Transport ◽  
Amino Acid Transport System ◽  
Transcellular Transport ◽  
System A

Trans-placental transport of amino acids is vital for the developing fetus. Using the BeWo cell line as a placental model, we investigated the effect of restricting amino acid availability on amino acid transport system type A. BeWo cells were cultured either in amino acid-depleted (without non-essential amino acids) or control media for 1, 3, 5 or 6 h. System A function was analysed using α(methyl-amino)isobutyric acid (MeAIB) transcellular transport studies. Transporter (sodium coupled neutral amino acid transporter (SNAT1/2)) expression was analysed at mRNA and protein level by Northern and Western blotting respectively. Localisation was carried out using immunocytochemistry. MeAIB transcellular transport was significantly (P< 0.05) increased by incubation of the cells in amino acid-depleted medium for 1 h, and longer incubation times caused further increases in the rate of transfer. However, the initial response was not accompanied by an increase in SNAT2 mRNA; this occurred only after 3 h and further increased for the rest of the 6-h incubation. Similarly, it took several hours for a significant increase in SNAT2 protein expression. In contrast, relocalisation of existing SNAT2 transporters occurred within 30 min of amino acid restriction and continued throughout the 6-h incubation. When the cells were incubated in medium with even lower amino acid levels (without non-essential plus 0.5 × essential amino acids), SNAT2 mRNA levels showed further significant (P< 0.0001) up-regulation. However, incubation of cells in depleted medium for 6 h caused a significant (P= 0.014) decrease in the expression of SNAT1 mRNA. System L type amino acid transporter 2 (LAT2) expression was not changed by amino acid restriction, indicating that the responses seen in the system A transporters were not a general cell response. These data have shown that placental cells adaptin vitroto nutritional stress and have identified the physiological, biochemical and genomic mechanisms involved.

Characterization and regulation of the gene expression of amino acid transport system A (SNAT2) in rat mammary gland

2006 ◽  
Vol 291 (5) ◽  
pp. E1059-E1066 ◽  
Author(s):  
Adriana López ◽  
Nimbe Torres ◽  
Victor Ortiz ◽  
Gabriela Alemán ◽  
Rogelio Hernández-Pando ◽  
...  
Keyword(s):  
Gene Expression ◽  
Amino Acids ◽  
Mammary Gland ◽  
Amino Acid ◽  
Transport System ◽  
Amino Acid Transport ◽  
Acid Transport ◽  
Amino Acid Transport System ◽  
System A ◽  
Rat Mammary Gland

Amino acid transport via system A plays an important role during lactation, promoting the uptake of small neutral amino acids, mainly alanine and glutamine. However, the regulation of gene expression of system A [sodium-coupled neutral amino acid transporter (SNAT)2] in mammary gland has not been studied. The aim of the present work was to understand the possible mechanisms of regulation of SNAT2 in the rat mammary gland. Incubation of gland explants in amino acid-free medium induced the expression of SNAT2, and this response was repressed by the presence of small neutral amino acids or by actinomycin D but not by large neutral or cationic amino acids. The half-life of SNAT2 mRNA was 67 min, indicating a rapid turnover. In addition, SNAT2 expression in the mammary gland was induced by forskolin and PMA, inducers of PKA and PKC signaling pathways, respectively. Inhibitors of PKA and PKC pathways partially prevented the upregulation of SNAT2 mRNA during adaptive regulation. Interestingly, SNAT2 mRNA was induced during pregnancy and to a lesser extent at peak lactation. β-Estradiol stimulated the expression of SNAT2 in mammary gland explants; this stimulation was prevented by the estrogen receptor inhibitor ICI-182780. Our findings clearly demonstrated that the SNAT2 gene is regulated by multiple pathways, indicating that the expression of this amino acid transport system is tightly controlled due to its importance for the mammary gland during pregnancy and lactation to prepare the gland for the transport of amino acids during lactation.

Amino acids are compatible osmolytes for volume recovery after hypertonic shrinkage in vascular endothelial cells

1999 ◽  
Vol 276 (4) ◽  
pp. C865-C872 ◽  
Author(s):  
Valeria Dall’Asta ◽  
Ovidio Bussolati ◽  
Roberto Sala ◽  
Alessandro Parolari ◽  
Francesco Alamanni ◽  
...  
Keyword(s):  
Amino Acids ◽  
Endothelial Cells ◽  
Amino Acid ◽  
Cell Volume ◽  
Transport System ◽  
Vascular Endothelial Cells ◽  
Human Endothelial Cells ◽  
Hypertonic Stress ◽  
System A ◽  
Compatible Osmolytes

The response to chronic hypertonic stress has been studied in human endothelial cells derived from saphenous veins. In complete growth medium the full recovery of cell volume requires several hours and is neither associated with an increase in cell K+ nor hindered by bumetanide but depends on an increased intracellular pool of amino acids. The highest increase is exhibited by neutral amino acid substrates of transport system A, such as glutamine and proline, and by the anionic amino acid glutamate. Transport system A is markedly stimulated on hypertonic stress, with an increase in activity roughly proportional to the extent and the duration of the osmotic shrinkage. Cycloheximide prevents the increase in transport activity of system A and the recovery of cell volume. It is concluded that human endothelial cells counteract hypertonic stress through the stimulation of transport system A and the consequent expansion of the intracellular amino acid pool.

Characterization of a broad-scope amino acid transport system in sand dollars

1988 ◽  
Vol 254 (3) ◽  
pp. R485-R490 ◽  
Author(s):  
J. P. Davis ◽  
S. Bellis ◽  
G. C. Stephens
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Transport System ◽  
Isobutyric Acid ◽  
Amino Acid Transport System ◽  
Neutral Amino Acids ◽  
Broad Scope ◽  
Alanine Transport ◽  
Sand Dollars

Both echinoderm embryos and adults take up alpha-amino acids by an apparent broad-scope transport system. This transporter can be characterized as follows: alanine transport is not blocked by alpha-(methylamino)isobutyric acid. Leucine and other lipophilic neutral amino acids are preferentially transported. Transport is sodium dependent and blocked by 2-aminobicyclo-[2,2,1]heptane-2-carboxycylic acid. Lysine and aspartate transport is inhibited by lipophilic neutral amino acids. Taurine, a beta-neutral amino acid, is translocated via a second and independent carrier.

scholarly journals Transport of the aromatic amino acids into isolated rat liver cells. Properties of uptake by two distinct systems

1986 ◽  
Vol 233 (2) ◽  
pp. 499-506 ◽  
Author(s):  
M Salter ◽  
R G Knowles ◽  
C I Pogson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Liver ◽  
Transport System ◽  
Aromatic Amino Acids ◽  
Liver Cells ◽  
Transport Systems ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

The transport of the aromatic amino acids into isolated rat liver cells was studied. There was a rapid and substantial binding of the aromatic amino acids, L-alanine and L-leucine to the plasma membrane. This has important consequences for the determination of rates of transport and intracellular concentrations of the amino acids. Inhibition studies with a variety of substrates of various transport systems gave results consistent with aromatic amino acid transport being catalysed by two systems: a 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH)-insensitive aromatic D- and L-amino acid-specific system, and the L-type system (BCH-sensitive). The BCH-insensitive component of transport was Na+-independent and facilitated non-concentrative transport of the aromatic amino acids; it was unaffected by culture of liver cells for 24 h, by 48 h starvation, dexamethasone phosphate or glucagon. Kinetic properties of the BCH-inhibitable component were similar to those previously reported for the L2-system in liver cells. The BCH-insensitive component was a comparatively low-Km low-Vmax. transport system that we suggest is similar to the T-transport system previously seen only in human red blood cells. The results are discussed with reference to the importance of the T- and L-systems in the control of aromatic L-amino acid degradation in the liver.

Ionic requirements of peritubular taurine transport in Fundulus kidney

1986 ◽  
Vol 250 (6) ◽  
pp. R984-R990 ◽  
Author(s):  
N. A. Wolff ◽  
D. F. Perlman ◽  
L. Goldstein
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Fundulus Heteroclitus ◽  
The Other ◽  
Renal Tubules ◽  
Taurine Transport ◽  
System A ◽  
Absolute Requirement ◽  
Relationship Of ◽  
Taurine Uptake

A peritubular mechanism for active taurine uptake, similar to that previously found in the flounder, was demonstrated in killifish (Fundulus heteroclitus) teased renal tubules. Other beta-amino acids and glycine inhibited taurine transport. Uptake exhibited a nearly absolute requirement for external Na+. The stoichiometric relationship between Na+ and taurine was found to be 2:1. Medium Cl- markedly stimulated the Na+-dependent taurine uptake, but none of the other small monovalent anions tested (NO3-, Br-, SCN-) could substitute for Cl- in activating taurine transport. Cl- replacement resulted in a significant decrease in V max, whereas the affinity of the carrier for taurine appeared to be unaffected. In the absence of Cl- the Na+ dependence of taurine influx was reduced to a stoichiometric relationship of 1.4 Na+:1 taurine, indicating an effect of Cl- on the binding of Na+ to the transport system. A model for Na+ -Cl- -taurine cotransport is presented.

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