Ca2+-dependence of the evoked release from guinea pig cerebral cortex slices of endogenous 14C-labelled amino acids, labelled via D-[U-14C]glucose

1976 ◽  
Vol 54 (6) ◽  
pp. 953-956 ◽  
Author(s):  
S. J. Potashner
Keyword(s):  
Amino Acids ◽  
Cerebral Cortex ◽  
Amino Acid ◽  
Guinea Pig ◽  
The Other ◽  
Major Portion ◽  
Free Medium ◽  
Spontaneous Release ◽  
Endogenous Amino Acids ◽  
Cortex Slices

Spontaneous and electrically evoked release of exogenous labelled amino acids and endogenous amino acids labelled from D-[U-14C]glucose were compared in control and Ca2+-free medium using guinea pig cerebral cortex slices. Spontaneous release of all labelled amino acids, except that of endogenous 14C-labelled threonine–serine–glutamine (unseparated) and exogenous [14C]aspartate, was doubled in Ca2+-free medium. The major portion of the electrically evoked release of endogenous [14C]glutamate, [14C]aspartate, γ-amino[14C]butyrate (14C-labelled GABA) and exogenous 3H-labelled GABA was Ca2+-dependent. More than half of the evoked release of the other labelled amino acids was Ca2+-independent. As the pattern of Ca2+-dependence of the evoked releases concurred with the selectivity of the evoked release for endogenous [14C]-glutamate, [14C]aspartate, and 14C-labelled GABA, it was concluded that these labelled amino acids were probably released from the amino acid 'transmitter pool'.

Evoked release from guinea pig cerebral cortex slices of endogenous 14C-labelled amino acids, labelled via D-[U-14C]glucose

1976 ◽  
Vol 54 (6) ◽  
pp. 949-952 ◽  
Author(s):  
S. J. Potashner
Keyword(s):  
Amino Acids ◽  
Cerebral Cortex ◽  
Guinea Pig ◽  
Electrical Field Stimulation ◽  
Mammalian Brain ◽  
Field Stimulation ◽  
Electrical Field ◽  
Endogenous Amino Acids ◽  
Cortex Slices

Release of endogenous amino acids labelled via D-[U-14C]glucose was compared with that of several exogenous labelled amino acids using slices of guinea pig cerebral cortex. Electrical field stimulation evoked a selective release of endogenous [14C]glutamate, [14C]aspartate, and γ-amino[14C]butyrate (14C-labelled GABA). The selectivity of release correlated well with 14C incorporation into endogenous amino acids. Calculations of the fraction of the tissue radio-activity released indicated that the selectivity was not an artifact due to differential incorporation. Because glucose in mammalian brain is metabolized almost entirely by the so-called 'large compartment', it is tentatively concluded that the releasable 'transmitter pool' of glutamate, aspartate, and GABA is located in this 'large compartment'.

Binding and Uptake of Amino Acids by Brain Tissue

1973 ◽  
Vol 51 (2) ◽  
pp. 121-128 ◽  
Author(s):  
P. C. Shiu ◽  
K. A. C. Elliott
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Sodium Chloride ◽  
Incubation Medium ◽  
Sucrose Solution ◽  
The Other ◽  
Percentage Increase ◽  
Endogenous Amino Acids ◽  
Sodium Dependent ◽  
Net Uptake

(1) Of the endogenous glutamate, aspartate, alanine, glycine, and γ-aminobutyrate (GABA), 26–37% remains bound in particles when rat brain is homogenized in isosmotic salt-free sucrose solution; a smaller proportion, 16%, of the glutamine is bound. The amounts bound are increased if sodium chloride is present; the percentage increase is greatest in the case of GABA, followed by glutamate, and least with glutamine. When tracer amounts of radioactive amino acids are present in the solution in the absence of salt very little radioactivity appears in bound GABA or glutamine, but appreciable amounts are found in the other amino acids. In the presence of sodium chloride, the total amount of bound amino acid increases as does, to a lesser extent, the radioactivity bound. Ouabain and protoveratrine seem to cause some release of sodium-dependent binding of the amino acids; this is most marked with GABA.(2) Slices incubated in the presence of oxygen and glucose take up each of the amino acids when these are added to the incubation medium. The highest intracellular concentration and the greatest net uptake occur with GABA. The endogenous concentration of glutamate is higher than that of the other amino acids but the net uptake is the least. The highest ratios of uptake to endogenous content occur with alanine and glycine. Determinations of radioactivity indicate that, in the cases of GABA and glycine, the increase in radioactivity in the slices is almost completely accounted for by uptake from the medium with almost no exchange. Some exchange occurs with other amino acids. Protoveratrine inhibits uptake of all the amino acids and actually causes loss of glutamate and aspartate from slices. Ouabain inhibits in all cases; the uptakes of glutamate and aspartate are least affected. Tetrodotoxin, alone or with either of the other two drugs, tends to increase uptake of all the amino acids. When the net uptake is inhibited by drugs considerable exchange of endogenous amino acids with radioactive amino acids in the medium is observed.

scholarly journals Conversion of glutamate into aspartate in guinea-pig cerebral-cortex slices

1968 ◽  
Vol 107 (1) ◽  
pp. 109-111 ◽  
Author(s):  
Gerald Simon ◽  
M. M. Cohen ◽  
J. F. Berry
Keyword(s):  
Cerebral Cortex ◽  
Amino Acid ◽  
Citric Acid ◽  
Guinea Pig ◽  
Amino Acid Metabolism ◽  
Citric Acid Cycle ◽  
Acid Metabolism ◽  
Acid Cycle ◽  
Cortex Slices

1. When guinea-pig cerebral-cortex slices were incubated with [U−14C]glutamate as substrate, the specific radioactivities of the citric acid-cycle intermediates were lower than that of the aspartate isolated from the same vessels. 2. Aspartate was significantly labelled when [5−14C]glutamate was used as substrate and the aspartate contained almost no label when [1−14C]glutamate was present as substrate. 3. When specifically labelled glutamate was used as substrate, the label was found in the isolated aspartate in the position that would be predicted by citric acid-cycle mechanisms. 4. The results are consistent with the theory of ‘compartmentation’ of amino acid metabolism.

METABOLISM OF AROMATIC COMPOUNDS IN HEALTHY AND RUST-INFECTED PRIMARY LEAVES OF WHEAT: II. STUDIES WITH L-PHENYLALANINE-U-14C, L-TYROSINE-U-14C, AND FERULATE-U-14C

1967 ◽  
Vol 45 (11) ◽  
pp. 2137-2153 ◽  
Author(s):  
A. Fuchs ◽  
R. Rohringer ◽  
D. J. Samborski
Keyword(s):  
Amino Acids ◽  
Stem Rust ◽  
Aromatic Compounds ◽  
The Other ◽  
Major Portion ◽  
Insoluble Residue ◽  
Resistant Reaction ◽  
Wheat Leaves

Wheat leaves infected with stem rust, especially those of susceptible plants, contained more phenylalanine and tyrosine than healthy leaves. The utilization of phenylalanine was increased in both the susceptible and resistant reaction, but the utilization of tyrosine was increased only in the susceptible reaction. No evidence of interconversion of these amino acids was obtained.In n-butanol extracts, which contained glycosides, many constituents were labelled after feeding of L-phenylalanine-U-14C. Most of the n-butanol extractives from resistant-reacting leaves contained more label than those from susceptible-reacting leaves or from healthy leaves. However, one of the n-butanol extractives from susceptible-reacting leaves was 5–10 times as active as that isolated from the other tissues.With L-phenylalanine-U-14C and ferulate-U-14C as precursors, more activity was recovered in insoluble than in soluble esters (of ferulate and p-coumarate). With L-tyrosine-U-14C as precursor, the reverse was observed. After infection, the proportion of label in insoluble esters increased more in resistant leaves than it did in susceptible leaves, regardless of the precursor used.A major portion of the activity from these precursors was recovered in the insoluble residue that contained protein and other polymers. In the experiment with L-phenylalanine-U-14C, this residue was fractionated into protein and non-hydrolyzable material. Susceptible-reacting leaves contained equal amounts of activity in these fractions, while resistant-reacting leaves incorporated 2.5 times as much activity into the non-hydrolyzable material as into protein.

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.

Effect of (-)nicotine on GABA efflux from guinea pig cerebral cortex slices

1989 ◽  
Vol 21 ◽  
pp. 133-134 ◽  
Author(s):  
P. Spalluto ◽  
M. Morari ◽  
L. Ferraro ◽  
A. Nordberg ◽  
T. Antonelli ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Guinea Pig ◽  
Cortex Slices
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