Nonparticipation of extracellular glutathione in renal transport of dibasic amino acids

1979 ◽  
Vol 57 (10) ◽  
pp. 1168-1171 ◽  
Author(s):  
André G. Craan ◽  
Michel Bergeron
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Proximal Tubules ◽  
Methionine Sulfoximine ◽  
Acid Transport ◽  
Intracellular Glutathione ◽  
Direct Competition ◽  
Dibasic Amino Acid ◽  
Dibasic Amino Acids

Microinjections of L-[14C]arginine (2.9 mM) and L-[14C]ornithine (3.4 mM) were made into renal proximal tubules of rats in the presence of methionine sulfoximine (MSO) (10, 20 mM), ATP (10 mM), and MgCl2 (20 mM) together. Absorption of both labelled amino acids dropped, respectively, by 31.1 and 49.1% compared with control microinjections. The MSO alone or ATP plus MgCl2 had no effect. These data suggest that the inhibition by MSO plus ATP plus MgCl2 is not due to direct competition between MSO and dibasic amino acids but rather to suppression of the renewal of intracellular glutathione. Such an effect is discussed in comparison with cycloleucine inhibition of dibasic amino acid transport. Addition of exogenous glutathione to microinjectates did not reverse either type of inhibition. This study shows that while intracellular glutathione may affect amino acid transport, extracellular glutathione has no effect.

Amino acid transport in human and in sheep erythrocytes

1980 ◽  
Vol 209 (1176) ◽  
pp. 355-375 ◽  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Acid Transport ◽  
Sheep Erythrocytes ◽  
Neutral Amino Acids ◽  
L System ◽  
Dibasic Amino Acids

Amino acid transport was compared in human and in sheep erythrocytes. Kinetic studies established that human cells have three discrete amino acid transport systems, designated L, Ly + and ASC. The L system is partially stereospecific, with a preference for large neutral amino acids. L-leucine has a threefold lower apparent K m and a twofold smaller V max than D-leucine. Alanine, cysteine and possibly dibasic amino acids are transported by this route, but with a low affinity. The Ly + system is highly stereoselective, and specific for dibasic amino acids, including arginine. The ASC system is Na-dependent and selective for neutral amino acids of intermediate size. It has a particularly low apparent K m for cysteine and is stereospecific. Sheep erythrocytes lack these systems. Instead they possess an additional system (C system) responsible for the transport both of neutral and of dibasic amino acids, with cysteine as the optimal substrate. Although the substrate specificities of the human ASC and sheep C systems are similar, the sheep system does not require Na and has considerably higher apparent K m values. Dibasic amino acid transport (of lysine, but not of arginine) by the C system occurs with a low affinity.

scholarly journals Substrate specificity of amino acid transport in sheep erythrocytes

1977 ◽  
Vol 162 (1) ◽  
pp. 33-38 ◽  
Author(s):  
J D Young ◽  
J C Ellory
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Acid Transport ◽  
Inhibitory Potency ◽  
Amino Acid Transport System ◽  
Specific Amino Acid ◽  
Sheep Erythrocytes ◽  
Alpha Beta ◽  
Dibasic Amino Acids

The specificity of amino acid transport in normal (high-glutathione) sheep erythrocytes was investigated by studying the interaction of various neutral and dibasic amino acids in both competition and exchange experiments. Apparent Ki values were obtained for amino acids as inhibitors of L-alanine influx. Amino acids previously found to be transported by high-glutathione cells at fast rates (L-cysteine, L-alpha-amino-n-butyrate) were the most effective inhibitors. D-Alanine and D-alpha-amino-n-butyrate were without effect. Of the remaining amino acids studied, only L-norvaline, L-valine, L-norleucine, L-serine and L-2,4-diamino-n-butyrate significantly inhibited L-alanine uptake. L-Alanine efflux from pre-loaded cells was markedly stimulated by extracellular L-alanine. Those amino acids that inhibited L-alanine influx also stimulated L-alanine efflux. In addition, D-alanine, D-alpha-amino-n-biutyrate, L-threonine, L-asparagine, L-alpha, beta-diaminoproprionate, L-ornithine, L-lysine and S-2-aminoethyl-L-cysteine also significantly stimulated L-alanine efflux. L-Lysine uptake was inhibited by L-alanine but not by D-alanine, and the inhibitory potency of L-alanine was not influenced by the replacement of Na+ in the incubation medium with choline. L-Lysine efflux from pre-loaded cells was stimulated by L-alanine but not by D-alanine. It is concluded that these cells possess a highly selective stero-specific amino acid-transport system. Although the optimum substrates are small neutral amino acids, this system also has a significant affinity for dibasic amino acids.

scholarly journals Competitive Inhibition of Dibasic Amino Acid Transport in Rat Kidney

1962 ◽  
Vol 237 (7) ◽  
pp. 2265-2270
Author(s):  
Leon E. Rosenberg ◽  
Sylvia J. Downing ◽  
Stanton Segal
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Competitive Inhibition ◽  
Rat Kidney ◽  
Acid Transport ◽  
Dibasic Amino Acid

scholarly journals Amino acid transport in normal and glutathione-deficient sheep erythrocytes

1976 ◽  
Vol 154 (1) ◽  
pp. 43-48 ◽  
Author(s):  
J D Young ◽  
J C Ellory ◽  
E M Tucker
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Cell Types ◽  
The Other ◽  
Acid Transport ◽  
Sheep Erythrocytes ◽  
Uptake Rates

1. Uptake rates for 23 amino acids were measured for both normal (high-GSH) and GSH-deficient (low-GSH) erythrocytes from Finnish Landrace sheep. 2. Compared with high-GSH cells, low-GSH cells had a markedly diminished permeability to D-alanine, L-alanine, α-amino-n-butyrate, valine, cysteine, serine, threonine, asparagine, lysine and ornithine. Smaller differences were observed for glycine and proline, whereas uptake of the other amino acids was not significantly different in the two cell types.

Amino Acid Transport in a Water-mould: The Possible Regulatory Roles of Calcium and N6-(Δ2-isopentenyl)adenine

1975 ◽  
Vol 53 (9) ◽  
pp. 975-988 ◽  
Author(s):  
Danny P. Singh ◽  
Hérb. B. LéJohn
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Osmotic Shock ◽  
Inhibitory Effect ◽  
Transport Systems ◽  
Acid Transport ◽  
Isopentenyl Adenine ◽  
Energy Dependent ◽  
Water Mould

Transport of amino acids in the water-mould Achlya is an energy-dependent process. Based on competition kinetics and studies involving the influence of pH and temperature on the initial transport rates, it was concluded that the 20 amino acids (L-isomers) commonly found in proteins were transported by more than one, possibly nine, uptake systems. This is similar to the pattern elucidated for some bacteria but unlike those uncovered for all fungi studied to date. The nine different transport systems elucidated are: (i) methionine, (ii) cysteine, (iii) proline, (iv) serine–threonine, (v) aspartic and glutamic acids, (vi) glutamine and asparagine, (vii) glycine and alanine, (viii) histidine, lysine, and arginine, and (ix) phenylalanine–tyrosine–tryptophan and leucine–isoleucine–valine as two overlapping groups. Transport of all of these amino acids was inhibited by azide, cyanide, and its derivatives and 2,4-dinitrophenol. These agents normally interfere with metabolism at the level of the electron transport chain and oxidative phosphorylation. Osmotic shock treatment of the cells released, into the shock fluid, a glycopeptide that binds calcium as well as tryptophan but no other amino acid. The shocked cells are incapable of concentrating amino acids, but remain viable and reacquire this capacity when the glycopeptide is resynthesized.Calcium played more than a secondary role in the transport of the amino acids. When bound to the membrane-localized glycopeptide, it permits concentrative transport to take place. However, excess calcium can inhibit transport which can be overcome by chelating with citrate. Calculations show that the concentration of free citrate is most important. At low citrate concentrations (less than 1 mM) in the absence of exogenously supplied calcium, enhancement of amino acid transport occurs. At high concentrations (greater than 5 mM), citrate inhibits but this effect can be reversed by titrating with calcium. Evidently, the glycopeptide acts as a calcium sink to regulate the concentration of calcium made available to the cell for its membrane activities.N6-(Δ2-isopentenyl) adenine (a plant growth 'hormone') and analogues mimic the inhibitory effect of citrate and bind to the glycopeptide as well. Replot data for citrate and N6-(Δ2-isopentyl) adenine inhibition indicate that both agents have no more than one binding constant. These results implicate calcium, glycopeptide, and energy-dependent transport of solutes in some, as yet undefinable, way.

Placental amino acid transport

1995 ◽  
Vol 268 (6) ◽  
pp. C1321-C1331 ◽  
Author(s):  
A. J. Moe
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Human Placenta ◽  
Amino Acid Transport ◽  
Single Layer ◽  
Maternal Blood ◽  
Transport Systems ◽  
Amino Acid Transporters ◽  
Acid Transport ◽  
Principal Mechanism

Normal fetal growth and development depend on a continuous supply of amino acids from the mother to the fetus. The placenta is responsible for the transfer of amino acids between the two circulations. The human placenta is hemomonochorial, meaning that the maternal and fetal circulations are separated by a single layer of polarized epithelium called the syncytiotrophoblast, which is in direct contact with maternal blood. Transport proteins located in the microvillous and basal membranes of the syncytiotrophoblast are the principal mechanism for transfer from maternal blood to fetal blood. Knowledge of the function and regulation of syncytiotrophoblast amino acid transporters is of great importance in understanding the mechanism of placental transport and potentially improving fetal and newborn outcomes. The development of methods for the isolation of microvillous and basal membrane vesicles from human placenta over the past two decades has contributed greatly to this understanding. Now a primary cultured trophoblast model is available to study amino acid transport and regulation as the cells differentiate. The types of amino acid transporters and their distribution between the syncytiotrophoblast microvillous and basal membranes are somewhat unique compared with other polarized epithelia. These differences may reflect the unusual circumstance of this epithelium that is exposed to blood on both sides. The current state of knowledge as to the types of transport systems present in syncytiotrophoblast, their regulation, and the effects of maternal consumption of drugs on transport are discussed.

Multiple pathways for cationic amino acid transport in rat thyroid epithelial cell line PC Cl3

2005 ◽  
Vol 288 (2) ◽  
pp. C290-C303 ◽  
Author(s):  
Tiziano Verri ◽  
Cinzia Dimitri ◽  
Sonia Treglia ◽  
Fabio Storelli ◽  
Stefania De Micheli ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Line ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Residual Fraction ◽  
Acid Transport ◽  
Thyroid Cells ◽  
Cationic Amino Acid ◽  
Rat Thyroid

Information regarding cationic amino acid transport systems in thyroid is limited to Northern blot detection of y+LAT1 mRNA in the mouse. This study investigated cationic amino acid transport in PC cell line clone 3 (PC Cl3 cells), a thyroid follicular cell line derived from a normal Fisher rat retaining many features of normal differentiated follicular thyroid cells. We provide evidence that in PC Cl3 cells plasmalemmal transport of cationic amino acids is Na+ independent and occurs, besides diffusion, with the contribution of high-affinity, carrier-mediated processes. Carrier-mediated transport is via y+, y+L, and b0,+ systems, as assessed by l-arginine uptake and kinetics, inhibition of l-arginine transport by N-ethylmaleimide and neutral amino acids, and l-cystine transport studies. y+L and y+ systems account for the highest transport rate (with y+L > y+) and b0,+ for a residual fraction of the transport. Uptake data correlate to expression of the genes encoding for CAT-1, CAT-2B, 4F2hc, y+LAT1, y+LAT2, rBAT, and b0,+AT, an expression profile that is also shown by the rat thyroid gland. In PC Cl3 cells cationic amino acid uptake is under TSH and/or cAMP control (with transport increasing with increasing TSH concentration), and upregulation of CAT-1, CAT-2B, 4F2hc/y+LAT1, and rBAT/b0,+AT occurs at the mRNA level under TSH stimulation. Our results provide the first description of an expression pattern of cationic amino acid transport systems in thyroid cells. Furthermore, we provide evidence that extracellular l-arginine is a crucial requirement for normal PC Cl3 cell growth and that long-term l-arginine deprivation negatively influences CAT-2B expression, as it correlates to reduction of CAT-2B mRNA levels.

Amino-acid-dependent modulation of amino acid transport in Xenopus laevis oocytes.

1996 ◽  
Vol 199 (4) ◽  
pp. 923-931 ◽  
Author(s):  
P M Taylor ◽  
S Kaur ◽  
B Mackenzie ◽  
G J Peter
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Xenopus Laevis ◽  
Amino Acid Transport ◽  
Acid Mixture ◽  
Xenopus Laevis Oocytes ◽  
Amino Acid Transporters ◽  
Amino Acid Supplementation ◽  
Acid Transport ◽  
Acid Supplementation

We have measured rates of uptake of arginine, glutamine, glutamate, serine, phenylalanine and glycine in Xenopus laevis oocytes cultured for periods of up to 24h in saline in the presence or absence of a mixture of 20 amino acids at concentrations approximating those in Xenopus plasma. Amino acid supplementation increased the total intracellular amino acid concentration from 8.2 to 18.4 nmol per oocyte. Specific Na(+)-dependent amino acid transporters (systems B0,+, Xag-) exhibit 'adaptive regulation' (up-regulation during amino acid deprivation and down-regulation during amino acid supplementation). Na(+)-independent transporters of glutamate, glutamine and glycine (including system asc) display an opposite modulation in activity, which may help to combat amino-acid-induced oxidative stress by increasing the supply of glutathione precursors. Single amino acids at physiological plasma concentrations (0.47 mmol l-1 L-alanine, 0.08 mmol l-1 L-glutamate) mimicked at least some effects of the amino acid mixture. The mechanisms of transport modulation do not appear to include trans-amino acid or membrane potential effects and, in the case of Na(+)-independent transport, are independent of protein or mRNA synthesis. Furthermore, activation of protein kinase C by phorbol 12-myristate 13-acetate did not significantly affect endogenous glutamine and glutamate transport. The Xenopus oocyte appears to possess endogenous signalling mechanisms for selectively modulating the activity of amino acid transport proteins expressed in its surface membranes, a factor for consideration when using oocytes as an expression system for structure-function studies of cloned amino acid transporters.

Cloning and functional characterization of a new subtype of the amino acid transport system N

2001 ◽  
Vol 281 (6) ◽  
pp. C1757-C1768 ◽  
Author(s):  
Takeo Nakanishi ◽  
Ramesh Kekuda ◽  
You-Jun Fei ◽  
Takahiro Hatanaka ◽  
Mitsuru Sugawara ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Transport System ◽  
Amino Acid Transport ◽  
Mammalian Cells ◽  
Functional Characterization ◽  
Isobutyric Acid ◽  
Xenopus Laevis Oocytes ◽  
Acid Transport ◽  
Amino Acid Transport System

We have cloned a new subtype of the amino acid transport system N2 (SN2 or second subtype of system N) from rat brain. Rat SN2 consists of 471 amino acids and belongs to the recently identified glutamine transporter gene family that consists of system N and system A. Rat SN2 exhibits 63% identity with rat SN1. It also shows considerable sequence identity (50–56%) with the members of the amino acid transporter A subfamily. In the rat, SN2 mRNA is most abundant in the liver but is detectable in the brain, lung, stomach, kidney, testis, and spleen. When expressed in Xenopus laevis oocytes and in mammalian cells, rat SN2 mediates Na+-dependent transport of several neutral amino acids, including glycine, asparagine, alanine, serine, glutamine, and histidine. The transport process is electrogenic, Li+tolerant, and pH sensitive. The transport mechanism involves the influx of Na+ and amino acids coupled to the efflux of H+, resulting in intracellular alkalization. Proline, α-(methylamino)isobutyric acid, and anionic and cationic amino acids are not recognized by rat SN2.

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