Evidence that cycloleucine affects the high-affinity systems of amino acid uptake in cultured human fibroblasts

The influence of cycloleucine on kinetic parameters of uptake of L-alanine, L-proline and L-leucine into cultured human fibroblasts was examined under initial-rate conditions with substrate concentrations of 0.05-10 mM and 5 mM-cycloleucine. Kinetic data obtained by computer analysis showed that, in the absence of cycloleucine, cell uptake was heterogeneous for each amino acid. L-Alanine and L-leucine entered by two transport systems with different affinities; L-proline was taken up by one saturable transport system plus a diffusion-like process. This heterogeneity disappeared in the presence of cycloleucine, since the high-affinity systems were no longer detectable. The remaining process had the same kinetic constants as the low-affinity system for alanine and leucine and a KD similar to the diffusion constant for proline. The influence of cycloleucine on the amino acid uptake was not specific either to the amino acid concerned or to a particular transport system, since the three neutral amino acid-transport systems, A, ASC and L, were involved in these experiments. This influence was shown to be unaffected by the absence of Na+ (for leucine uptake). ATP content of the cells was identical in the presence or in the absence of cycloleucine.

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Energization of amino acid uptake by system A in cultured human fibroblasts

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)52335-8 ◽

1991 ◽

Vol 266 (3) ◽

pp. 1591-1596

Author(s):

V Dall'Asta ◽

O Bussolati ◽

G G Guidotti ◽

G C Gazzola

Keyword(s):

Amino Acid ◽

Human Fibroblasts ◽

Amino Acid Uptake ◽

Acid Uptake ◽

System A ◽

Cultured Human Fibroblasts

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Normal amino acid uptake by cultured human fibroblasts does not require gamma-glutamyl transpeptidase

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(76)90221-7 ◽

1976 ◽

Vol 73 (4) ◽

pp. 997-1002 ◽

Cited By ~ 22

Author(s):

Francoise Pellefigue ◽

Jean DeBrohun Butler ◽

Stephen P. Spielberg ◽

Morley D. Hollenberg ◽

Stephen I. Goodman ◽

...

Keyword(s):

Amino Acid ◽

Human Fibroblasts ◽

Amino Acid Uptake ◽

Acid Uptake ◽

Gamma Glutamyl Transpeptidase ◽

Gamma Glutamyl ◽

Cultured Human Fibroblasts ◽

Glutamyl Transpeptidase

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Placental toxicology: tobacco smoke, abused drugs, multiple chemical interactions, and placental function

Reproduction Fertility and Development ◽

10.1071/rd9910355 ◽

1991 ◽

Vol 3 (4) ◽

pp. 355 ◽

Cited By ~ 91

Author(s):

BV Sastry

Keyword(s):

Amino Acid ◽

Amino Acid Transport ◽

Drugs Of Abuse ◽

Amino Acid Uptake ◽

Transport Systems ◽

Acid Uptake ◽

Acid Transport ◽

Ach Release ◽

Placental Blood ◽

Abused Drugs

There are increasing numbers of reports on the tobacco smoking and ingestion of abused drugs (e.g. morphine, cocaine) by pregnant women and the effects of the substances on the developing fetus and newborn infant. The passage of drugs and chemicals from the mother to the fetus is influenced by the placental transport and metabolism of the substances. Further, these drugs and chemicals affect the nutrient transport systems in the placenta. The three major drugs of abuse-nicotine, morphine and cocaine-depress both active amino-acid uptake by human placental villi and transplacental amino-acid transport by reason of the drugs' influence on placental cholinergic and opiate systems. Part of this depression (10-16%) is not reversible. Nicotine blocks the cholinergic receptor and thus blocks acetylcholine (ACh)-facilitated amino-acid transport. Morphine stimulates opiate kappa receptors and depresses ACh release. Cocaine blocks Ca2+ influx and thus blocks ACh release. ACh causes dilation of blood vessels and maintains placental blood flow by the activation of endothelial muscarinic receptors. By interfering with ACh release and placental blood flow, the three drugs of abuse may depress the diffusion of amino acids and other nutrients from the trophoblast into the placental circulation. Three regulatory systems are delineated for amino-acid uptake by the placenta: placental ACh, phospholipid N-methyltransferase, and the gammaglutamyl cycle. These systems operate in concert with one another and are dependent on cellular formation of adenosine 5'-triphosphate (ATP). Placental hypoxia induced by carbon monoxide and other tobacco gases depresses the energy-dependent processes and thus the ATP levels of placental cells. Maternal tobacco smoking and drug abuse cause placental insufficiencies for amino-acid transport, which may partially explain the fetal intrauterine growth retardation caused by these substances. Part of the amino-acid deficits may be compensated for by the induction of new amino-acid transport systems. Specific receptors or drug-binding proteins for the three drugs of abuse are present in the placenta. A DNA adduct selective for maternal smoking has been demonstrated in the placenta. DNA adducts selective for cocaine, morphine and other environmental chemicals have yet to be demonstrated ins the placenta.

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Amino acid uptake systems in Bacteroides ruminicola

Canadian Journal of Microbiology ◽

10.1139/m79-180 ◽

1979 ◽

Vol 25 (10) ◽

pp. 1161-1168 ◽

Cited By ~ 15

Author(s):

Roselynn M. W. Stevenson

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Nitrogen Sources ◽

Amino Acid Uptake ◽

Defined Medium ◽

High Rate ◽

Transport Systems ◽

Acid Uptake ◽

Chemical Structures ◽

Kinetic Inhibition

Uptake of amino acids by Bacteroides ruminicola was observed in cells grown in a complete defined medium, containing ammonia as the nitrogen source. A high rate of uptake occurred only in fresh medium, as an inhibitory substance, possibly acetate, apparently accumulated during growth. All amino acids except proline were taken up and incorporated into cold trichloroacetic acid precipitable material. Different patterns of incorporation and different responses to 2,4-dinitrophenol and potassium ferricyanide indicated multiple uptake systems were involved. Kinetic inhibition patterns suggested six distinct systems were present for amino acid uptake, with specificities related to the chemical structures of the amino acids. Thus, the failure of free amino acids to act as sole nitrogen sources for growth of B. ruminicola is not due to the absence of transport systems for these compounds.

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Arabidopsis LHT1 Is a High-Affinity Transporter for Cellular Amino Acid Uptake in Both Root Epidermis and Leaf Mesophyll

The Plant Cell ◽

10.1105/tpc.106.041012 ◽

2006 ◽

Vol 18 (8) ◽

pp. 1931-1946 ◽

Cited By ~ 186

Author(s):

Axel Hirner ◽

Friederike Ladwig ◽

Harald Stransky ◽

Sakiko Okumoto ◽

Melanie Keinath ◽

...

Keyword(s):

Amino Acid ◽

Amino Acid Uptake ◽

Acid Uptake ◽

Root Epidermis ◽

High Affinity ◽

Leaf Mesophyll

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Myocardial amino acid transport by canine sarcolemma vesicles

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1987.252.6.h1070 ◽

1987 ◽

Vol 252 (6) ◽

pp. H1070-H1076

Author(s):

L. H. Young ◽

B. L. Zaret ◽

E. J. Barrett

Keyword(s):

Amino Acid ◽

Sarcoplasmic Reticulum ◽

Membrane Vesicles ◽

Amino Acid Uptake ◽

Ventricular Myocardium ◽

Transport Systems ◽

Acid Uptake ◽

Leucine Uptake ◽

Alanine Transport ◽

Canine Ventricular Myocardium

The transport of L-alanine and L-leucine into membrane vesicles isolated from mature canine ventricular myocardium was studied. Transport was assessed in purified sarcolemma and in vesicles differentially enriched either for sarcolemma or sarcoplasmic reticulum to further localize these transport systems. An imposed inward gradient of a NaNO3 stimulated uptake of L-alanine but not L-leucine by these vesicles. Amino acid uptake by these vesicles occurred into an osmotically active space. The stimulatory effect of Na+ on alanine transport was most striking in the purified sarcolemma vesicles, where Na+-stimulated alanine flux was 45 +/- 14 pmol X mg-1 X min-1. Furthermore, Na+-dependent alanine transport activity appeared to copurify with Na+-K+-ATPase activity, which served as a marker for sarcolemma membrane when these activities were compared in the three different membrane preparations. Leucine transport by sarcolemma was not altered by an imposed Na+ gradient. However, leucine uptake was a saturable function of extravesicular leucine and was inhibited by valine. In contrast, in sarcoplasmic reticulum membrane vesicles leucine uptake increased proportionately with increasing media leucine and was unaffected by valine. Our results demonstrate the feasibility of directly studying the transport of naturally occurring amino acids in membrane vesicles from mammalian heart, and the presence of Na+-dependent alanine transport system and a Na+-independent leucine transporter in the sarcolemma but not in sarcoplasmic reticulum of canine ventricular myocardium.

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Amino Acid Uptake by Amino Acid Analog Resistant Tobacco Cell Lines

Zeitschrift für Naturforschung C ◽

10.1515/znc-1978-9-1005 ◽

1978 ◽

Vol 33 (9-10) ◽

pp. 634-640 ◽

Cited By ~ 14

Author(s):

Jochen Berlin ◽

Jade M. Widholm

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Cell Line ◽

Transport System ◽

Amino Acid Uptake ◽

Resistant Cell ◽

Resistant Cell Line ◽

Acid Uptake ◽

Wild Type ◽

Phenylalanine Transport

Abstract Two tobacco cell lines resistant to p-fiuorophenylalanine (PFP) and one resistant to 5-methyltryptophan (5-MT) are compared with wild type cells in their ability to absorb amino acids from the medium. One p-fluorophenylalanine-resistant cell line shows greatly reduced uptake of all amino acids so is resistant to growth inhibition by other amino acid analogs. The impaired absorption is noted with amino acids, amino acid analogs and shikimate, but not with cinnamate, salicylate, nicotine, glucose, 3-O-methylglucose and palmitate. The phenylalanine transport system of the PFP-resistant cell line and the wild type both have Km values of 90 µᴍ, but have different V max values. Several analogs of phenylalanine and several neutral L-amino acids inhibit the phenylalanine transport system, while ʟ-aspartic acid, ʟ-arginine, ᴅ-phenylalanine or chlorogenic acid do not interfere with the ʟ-phenylalanine uptake. The results indicate the presence of more than one transport system for amino acid uptake. The lessened uptake of all amino acids, the specificity of the uptake systems and the unchanged binding let us conclude that a pleiotropic mutation or that some inhibitor causes the reduced uptake of all amino acids by the PFP-resistant cell line.

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Glucocorticoids Enhance Somatomedin-C Binding and Stimulation of Amino Acid Uptake in Human Fibroblasts*

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem-64-3-563 ◽

1987 ◽

Vol 64 (3) ◽

pp. 563-571 ◽

Cited By ~ 13

Author(s):

PAUL B. KAPLOWITZ

Keyword(s):

Amino Acid ◽

Human Fibroblasts ◽

Amino Acid Uptake ◽

Acid Uptake ◽

Somatomedin C ◽

Stimulation Of

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In vivo muscle amino acid transport involves two distinct processes

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00092.2004 ◽

2004 ◽

Vol 287 (1) ◽

pp. E136-E141 ◽

Cited By ~ 23

Author(s):

Sharon Miller ◽

David Chinkes ◽

David A. MacLean ◽

Dennis Gore ◽

Robert R. Wolfe

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Amino Acid Transport ◽

Interstitial Fluid ◽

Muscle Blood Flow ◽

Amino Acid Uptake ◽

Transport Systems ◽

Acid Uptake ◽

Acid Transport ◽

Rate Limiting

We have tested the hypothesis that transit through the interstitial fluid, rather than across cell membranes, is rate limiting for amino acid uptake from blood into muscle in human subjects. To quantify muscle transmembrane transport of naturally occurring amino acids, we developed a novel 4-pool model that distinguishes between the interstitial and intracellular fluid compartments. Transport kinetics of phenylalanine, leucine, lysine, and alanine were quantified using tracers labeled with stable isotopes. The results indicate that interstitial fluid is a functional compartment insofar as amino acid kinetics are concerned. In the case of leucine and alanine, transit between blood and interstitial fluid was potentially rate limiting for muscle amino acid uptake and release in the postabsorptive state. For example, in the case of leucine, the rate of transport between blood and interstitial fluid compared with the corresponding rate between interstitial fluid and muscle was 247 ± 36 vs. 610 ± 95 nmol·min−1·100 ml leg−1, respectively ( P < 0.05). Our results are consistent with the process of diffusion governing transit from blood to interstitial fluid without selectivity, and of specific amino acid transport systems with varying degrees of efficiency governing transit from interstitial fluid to muscle. These results imply that changes in factors that affect the transit of amino acids from blood through interstitial fluid, such as muscle blood flow or edema, could play a major role in controlling the rate of muscle amino acid uptake.

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