The Role of Energy Metabolism in the Interaction between Amino Acid and Sugar Transport in the Small Intestine

1973 ◽  
Vol 51 (5) ◽  
pp. 378-382 ◽  
Author(s):  
I. Bihler ◽  
P. C. Sawh
Keyword(s):  
Amino Acid ◽  
Energy Metabolism ◽  
Sugar Transport ◽  
Intestinal Transport ◽  
Metabolic Energy ◽  
Acid Transport ◽  
Limited Supply ◽  
Everted Sacs

The interaction between sugar and amino acid transport was studied in everted sacs of rat jejunum in vitro. The addition of the actively transported nonmetabolized sugars, D-galactose and α-methyl-D-glucoside, to the mucosal medium inhibited the active transport of cycloleucine (1-amino-cyclopentane-1-carboxylic acid). This effect was largely counteracted by the simultaneous presence of D-glucose in the serosal medium or of D-fructose. The results indicate that provision of substrates for energy metabolism relieves the inhibition of transport and supports the hypothesis that the interaction between the intestinal transport of sugar and of amino acid is at least in part due to competition for a limited supply of metabolic energy.

Human placental acetylcholine

1991 ◽  
Vol 3 (4) ◽  
pp. 405 ◽  
Author(s):  
RG King ◽  
NM Gude ◽  
BR Krishna ◽  
S Chen ◽  
SP Brennecke ◽  
...  
Keyword(s):  
Blood Flow ◽  
Amino Acid ◽  
Cholinergic System ◽  
Vascular Tone ◽  
Perfusion Pressure ◽  
Acid Transport ◽  
Ach Release ◽  
Fetal Vessels

The human placenta contains both acetylcholine (ACh) and choline acetyltransferase, and in vitro bilaterally perfused placental lobules release ACh. The function of this placental cholinergic system has not yet been clearly defined, although changes occur in it during parturition and it may be linked to placental prostaglandin generation at this time. It has also been suggested that ACh may regulate placental amino-acid transport and/or blood flow. It has been found that ACh release from fetal vessels of bilaterally perfused placental lobules is reduced during preeclampsia but is not necessarily correlated with any change in perfusion pressure or materno-fetal transfer of the nonmetabolizable amino acid alpha-aminoisobutyric acid. However, a correlation has been found between releases from human placental explants of ACh (when inhibited by (2-benzoylethyl)trimethylammonium or vesamicol) and of prostaglandins E2 and F2 alpha. Thus, although the evidence for a role of ACh in the control of placental amino-acid transfer or vascular tone is not conclusive, inhibition of the human placental cholinergic system has been shown to be associated with reduced output of prostaglandins from this tissue.

scholarly journals Specificity of the HIV-1 Protease on Substrates Representing the Cleavage Site in the Proximal Zinc-Finger of HIV-1 Nucleocapsid Protein

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1092
Author(s):  
János András Mótyán ◽  
Márió Miczi ◽  
Stephen Oroszlan ◽  
József Tőzsér
Keyword(s):  
Amino Acid ◽  
Zinc Finger ◽  
Cleavage Site ◽  
Potential Role ◽  
Binding Mode ◽  
Interaction Energies ◽  
Vitro Assay ◽  
Hiv 1

To explore the sequence context-dependent nature of the human immunodeficiency virus type 1 (HIV-1) protease’s specificity and to provide a rationale for viral mutagenesis to study the potential role of the nucleocapsid (NC) processing in HIV-1 replication, synthetic oligopeptide substrates representing the wild-type and modified versions of the proximal cleavage site of HIV-1 NC were assayed as substrates of the HIV-1 protease (PR). The S1′ substrate binding site of HIV-1 PR was studied by an in vitro assay using KIVKCF↓NCGK decapeptides having amino acid substitutions of N17 residue of the cleavage site of the first zinc-finger domain, and in silico calculations were also performed to investigate amino acid preferences of S1′ site. Second site substitutions have also been designed to produce “revertant” substrates and convert a non-hydrolysable sequence (having glycine in place of N17) to a substrate. The specificity constants obtained for peptides containing non-charged P1′ substitutions correlated well with the residue volume, while the correlation with the calculated interaction energies showed the importance of hydrophobicity: interaction energies with polar residues were related to substantially lower specificity constants. Cleavable “revertants” showed one residue shift of cleavage position due to an alternative productive binding mode, and surprisingly, a double cleavage of a substrate was also observed. The results revealed the importance of alternative binding possibilities of substrates into the HIV-1 PR. The introduction of the “revertant” mutations into infectious virus clones may provide further insights into the potential role of NC processing in the early phase of the viral life-cycle.

Role of cysteine in jaundice hemorrhages

1935 ◽  
Vol 31 (8-9) ◽  
pp. 1114-1114
Keyword(s):  
Amino Acid ◽  
Obstructive Jaundice ◽  
Blood Clotting ◽  
In Vitro Experiments ◽  
Main Factor

The role of calcium, platelets, and other factors that were associated with bleeding was not confirmed in jaundice. Carr and Toote found that the amino acid cysteine was the main factor impeding blood clotting. In obstructive jaundice, this amino acid accumulates in the blood and in in vitro experiments and, when administered to animals, causes a deterioration in blood clotting.

scholarly journals Antagonists of the system L neutral amino acid transporter (LAT) promote endothelial adhesivity of human red blood cells

2017 ◽  
Vol 117 (07) ◽  
pp. 1402-1411 ◽  
Author(s):  
Laura Beth Mann Dosier ◽  
Vikram J. Premkumar ◽  
Hongmei Zhu ◽  
Izzet Akosman ◽  
Michael F. Wempe ◽  
...  
Keyword(s):  
Amino Acid ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Amino Acid Transporter ◽  
Neutral Amino Acid ◽  
Neutral Amino Acid Transporter ◽  
System L

SummaryThe system L neutral amino acid transporter (LAT; LAT1, LAT2, LAT3, or LAT4) has multiple functions in human biology, including the cellular import of S-nitrosothiols (SNOs), biologically active derivatives of nitric oxide (NO). SNO formation by haemoglobin within red blood cells (RBC) has been studied, but the conduit whereby a SNO leaves the RBC remains unidentified. Here we hypothesised that SNO export by RBCs may also depend on LAT activity, and investigated the role of RBC LAT in modulating SNO-sensitive RBC-endothelial cell (EC) adhesion. We used multiple pharmacologic inhibitors of LAT in vitro and in vivo to test the role of LAT in SNO export from RBCs and in thereby modulating RBC-EC adhesion. Inhibition of human RBC LAT by type-1-specific or nonspecific LAT antagonists increased RBC-endothelial adhesivity in vitro, and LAT inhibitors tended to increase post-transfusion RBC sequestration in the lung and decreased oxygenation in vivo. A LAT1-specific inhibitor attenuated SNO export from RBCs, and we demonstrated LAT1 in RBC membranes and LAT1 mRNA in reticulocytes. The proadhesive effects of inhibiting LAT1 could be overcome by supplemental L-CSNO (S-nitroso-L-cysteine), but not D-CSNO or L-Cys, and suggest a basal anti-adhesive role for stereospecific intercellular SNO transport. This study reveals for the first time a novel role of LAT1 in the export of SNOs from RBCs to prevent their adhesion to ECs. The findings have implications for the mechanisms of intercellular SNO signalling, and for thrombosis, sickle cell disease, and post-storage RBC transfusion, when RBC adhesivity is increased.

Impaired energy metabolism as an initial step in the mechanism for 6-aminonicotinamide-induced limb malformation

Development ◽  
1980 ◽  
Vol 59 (1) ◽  
pp. 217-222
Author(s):  
Yal C. Sheffield ◽  
Robert E. Seegmiller
Keyword(s):  
Amino Acid ◽  
Energy Metabolism ◽  
Chick Embryo ◽  
Chondroitin Sulfate ◽  
Atp Synthesis ◽  
Initial Step ◽  
Chick Embryos ◽  
Impaired Energy Metabolism ◽  
All Treatment

The analogue and antagonist of nicotinamide, 6-aminonicotinamide (6-AN), impairs cartilage formation and results in shortening of the limbs when administered to chick embryos. Studies have shown that 6-AN forms an abnormal NAD analogue which inhibits the activity of NAD-dependent enzymes associated with production of ATP. To determine if an effect on ATP synthesis might be associated with the mechanism of teratogenesis in the chick embryo, ATP levels of cartilage from day-8 chick embryos treated in vitro were assayed in relation to biosynthesis of protein, DNA and chondroitin sulfate. Incorporation of 35SO4− was inhibited by 6 h of treatment with 10 µg/ml of 6-AN, whereas incorporation of [3H]thymidine and [3H]amino acid was not inhibited until 12 h. Incorporation of [3H]- glucosamine was increased at all treatment times. A decrease in the level of ATP preceded any detectable inhibition of precursor incorporation. These results are consistent with the hypothesis that 6-AN inhibits chondroitin sulfate synthesis through a reduction in the level of ATP in chondrocytes.

Interaction between growth hormone and rat muscle in vitro

1961 ◽  
Vol 200 (4) ◽  
pp. 675-678 ◽  
Author(s):  
J. L. Kostyo ◽  
J. E. Schmidt
Keyword(s):  
Growth Hormone ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Growth Hormones ◽  
Hormone Concentration ◽  
Acid Transport ◽  
Rat Muscle ◽  
Resultant Effect ◽  
Initial Interaction

Hypophysectomized rat diaphragms, which were immersed briefly in dilute solutions of growth hormone and then washed thoroughly, subsequently transported α-aminoisobutyric acid-1-C14 at a greater rate than the controls. Growth hormones of bovine, porcine, simian and human origins were all effective. Increasing either the hormone concentration or the length of time that the diaphragms were immersed in growth hormone solutions increased the effect on amino acid transport. Prolonged washing of the diaphragms following exposure to growth hormone did not reduce the magnitude of the effect on amino acid transport. Moreover, reducing the temperature of the growth hormone solutions did not diminish the resultant effect on amino acid transport. From these results, it was concluded that the initial interaction between growth hormone and rat muscle in vitro occurs rapidly and the modification produced by this interaction is relatively stable.

scholarly journals The Role of Red Cell Energy Metabolism in the Generation of Irreversibly Sickled Cells In Vitro

Blood ◽  
1973 ◽  
Vol 42 (6) ◽  
pp. 835-842 ◽  
Author(s):  
Michael Jensen ◽  
Stephen B. Shohet ◽  
David G. Nathan
Keyword(s):  
Energy Metabolism ◽  
Calcium Metabolism ◽  
Red Cells ◽  
Red Cell ◽  
Hemoglobin S ◽  
Cell Energy ◽  
Incubation Buffer ◽  
Membrane Defect

Abstract An acquired membrane defect is believed to be responsible for the maintenance of the sickled shape in oxygenated irreversibly sickled cells (ISC), because the hemoglobin S in these cells is not in the aggregated, "sickled" state. In the present study, it is demonstrated that the acquisition of the membrane defect in vitro depends on cellular metabolism. Only if cellular ATP is almost completely depleted while the cells are sickled, do they become unable to resume the biconcave disk shape upon reoxygenation. If calcium is omitted from the incubation buffer, ISCs are not generated despite metabolic depletion. This suggests an action of ATP mediated through calcium metabolism similar to that which prevents membrane stiffening in normal red cells. No ISCs were produced by repeated sickling and unsickling. Thus, a membrane alteration occurring as a consequence of metabolic depletion seems to be a more important factor in the generation of ISC than sickling-unsickling induced fragmentation.

Role of the gamma-glutamyl cycle in the regulation of amino acid translocation

1989 ◽  
Vol 257 (6) ◽  
pp. E916-E922 ◽  
Author(s):  
J. R. Vina ◽  
M. Palacin ◽  
I. R. Puertes ◽  
R. Hernandez ◽  
J. Vina
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Acid Transport ◽  
Pregnant Rats ◽  
Gamma Glutamyl ◽  
Extracellular Signals ◽  
Previously Treated

Amino acid translocation was studied in the mammary gland of lactating rats and in the placenta of pregnant rats. The uptake of amino acids by the mammary gland is maximal on days 10-14 of lactation and is minimal on days 19-21. However, on day 19 maximal uptake can be restored by injection of 1) small amounts of gamma-glutamyl amino acids, 2) 5-oxoproline, and 3) an inhibitor of 5-oxoprolinase. A severe decrease in uptake of amino acids at the peak of lactation is provoked by anthglutin, an inhibitor of gamma-glutamyltranspeptidase (GGT). Simultaneous injection of 5-oxoproline blocks these effects of anthglutin. In pregnant rats, inhibition (79%) of placental GGT activity by acivicin results in a 50% decrease of placental L-[U-14C]-alanine transfer and 70-80% decrease in its incorporation into the placental and fetal proteins. Infusion of 5-oxoproline to mothers previously treated with acivicin restored the L-[U-14C]-alanine transfer. Acivicin or 5-oxoproline did not modify the transfer and metabolism of D-[U14C]glucose by the fetal placental unit. These results show that the gamma-glutamyl cycle should not be considered a mechanism for amino acid transport but rather a generator of extracellular signals, gamma-glutamyl amino acids, that are converted intracellularly to 5-oxoproline, which activates uptake and/or metabolism of amino acids.

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