scholarly journals Studies on brain-cortex slices. The influence of various inhibitors on the retention of potassium ions and amino acids with glucose or pyruvate as substrate

1967 ◽  
Vol 104 (1) ◽  
pp. 223-228 ◽  
Author(s):  
JE Cremer
Keyword(s):  
Amino Acids ◽  
Brain Cortex ◽  
Potassium Ions ◽  
Brain Cortex Slices ◽  
Cortex Slices

EFFECTS OF SODIUM PHENYLPYRUVATE ON AMINO ACID FORMATION IN BRAIN

1965 ◽  
Vol 43 (7) ◽  
pp. 835-840 ◽  
Author(s):  
T. Itoh
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brain Cortex ◽  
Acid Formation ◽  
Potassium Ions ◽  
Inhibitory Effects ◽  
High Potassium ◽  
Brain Cortex Slices ◽  
Cortex Slices ◽  
Intracellular Labelling

Rat brain cortex slices were incubated with glucose-U-C14 in normal Krebs–Ringer phosphate media and also media 105 mM in potassium ions. Intracellular labelling of amino acids, such as glutamic acid, glutamine, γ-aminobutyric acid, aspartic acid, and alanine, was estimated by radioautography according to the method of Kini and Quastel. The respiration of brain cortex slices was little affected by the presence of phenylpyruvate. However, the formation of these amino acids was strongly suppressed. Moreover, in high-potassium media, the inhibitory effects of phenylpyruvate were greatly magnified. The addition of phenylalanine had no significant effect either on the oxygen consumption or on the amino acid formation when brain cortex slices were incubated with glucose-U-C14.

Effects of acetylcholine on potassium-induced changes of some amino acid uptakes and release in cerebral cortex slices from the rat

1977 ◽  
Vol 55 (3) ◽  
pp. 347-355 ◽  
Author(s):  
A. M. Benjamin ◽  
J. H. Quastel
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Brain ◽  
Brain Cortex ◽  
Potassium Ions ◽  
Acid Uptake ◽  
Rat Brain Cortex ◽  
Brain Cortex Slices ◽  
High Concentrations ◽  
Cortex Slices

High concentrations (105 μequiv./ml) of potassium ions in the incubation medium bring about reduced uptakes of L-glutamate, L-aspartate, and glycine but not of L-glutamine into rat brain cortex slices incubated aerobically in a physiological saline – glucose medium. The reductions are suppressed by acetylcholine (20 μM – 2 mM) in presence of eserine (0.1 mM) and not by tetrodotoxin (3 μM). The effect of acetylcholine is calcium dependent. It is diminished by atropine but not by d-tubocurarine (1 mM). Protoveratrine (5 μM) inhibition of amino acid uptake is not affected by acetylcholine but it is suppressed by tetrodotoxin. Acetylcholine and tetrodotoxin act independently of each other. Acetylcholine suppresses the potassium-evoked release of endogenous glutamate, aspartate, or glycine from incubated rat brain cortex slices. Its action on release is calcium dependent. Acetylcholine also suppresses the potassium-induced release of amino acids from rat brain cortex slices that have been previously incubated with 2 mM sodium L-glutamate or 2 mM sodium L-aspartate.It is suggested that increased cell concentrations of calcium ions, owing to high concentrations of potassium ions in the incubation medium, cause an increased glial permeability to sodium ions, with a resultant diminution of the sodium gradient. This diminution is considered to be responsible for the diminished concentrative uptake of L-glutamate, L-aspartate, or glycine, and the increased release of these amino acids. Acetylcholine suppresses the permeability change due to high concentrations of potassium ions and reverses the changed sodium gradient and the consequent change in amino acid uptake and release. It would seem that accumulation of acetylcholine in the intracellular spaces may affect glia, as well as neurons, modifying permeability to sodium ions and to various amino acids now assuming importance as possible transmitters.

EFFECTS OF ACETYLSALICYLATE AND 2,4-DINITROPHENOL ON METABOLISM AND TRANSPORT IN RAT BRAIN CORTEX IN VITRO

1963 ◽  
Vol 41 (2) ◽  
pp. 435-454 ◽  
Author(s):  
O. Gonda ◽  
J. H. Quastel
Keyword(s):  
Amino Acids ◽  
Rat Brain ◽  
Brain Cortex ◽  
Transport Processes ◽  
Rat Brain Cortex ◽  
High K ◽  
Increased Sensitivity ◽  
Brain Cortex Slices ◽  
Cortex Slices

The effects of acetylsalicylate and of 2,4-dinitrophenol on the metabolism and transport processes of rat brain cortex slices incubated at 37° in glucose–Ringer media under various conditions have been investigated. The following processes are suppressed by acetylsalicylate (5 mM) or dinitrophenol (0.05 mM) to a much greater extent in media containing 105 mM KCl or 10 mM NH4Cl (which stimulate brain respiration) than in normal media:(a) respiration;(b) incorporation of phosphate into ATP and ADP;(c) conversion of creatine to phosphocreatine;(d) uptake of glutamate or of creatine from the medium to the tissue.The two drugs increase the leakage of amino acids from rat brain cortex slices into the medium, the effects being greatest in the presence of 105 mM KCl or 5 mM glutamate or in the absence of glucose. They change the yields of labelled amino acids from labelled glucose or labelled glutamate.Labelled glutamate is converted to labelled aspartate, γ-aminobutyrate and glutamine in rat brain cortex slices, the addition of glucose bringing about increased yields of glutamine and γ-aminobutyrate and a decreased yield of aspartate. The formation of labelled glutamine from either labelled glutamate or from labelled glucose is suppressed by acetylsalicylate or dinitrophenol, the effects being greater in the presence of 105 mM KCl or 10 mM NH4Cl.The increased sensitivity of the stimulated tissue metabolism to the drugs, in the presence of high K+, or of NH4+or of glutamate, is probably explained by the fact that there is a fall, under these conditions, in the tissue phosphocreatine level. There is, therefore, less reserve phosphocreatine to maintain the level of ATP when neuronal oxidative phosphorylation is suppressed by the addition of acetylsalicylate or of dinitrophenol.

AMINO ACID TRANSPORT IN BRAIN CORTEX SLICES: II. COMPETITION BETWEEN AMINO ACIDS

1962 ◽  
Vol 40 (11) ◽  
pp. 1591-1602 ◽  
Author(s):  
P. N. Abadom ◽  
P. G. Scholefield
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Brain ◽  
Amino Acid Transport ◽  
Brain Cortex ◽  
Transport Systems ◽  
Acid Transport ◽  
Inhibitory Effects ◽  
Brain Cortex Slices ◽  
Cortex Slices

Evidence is presented which indicates that several amino acid transport systems are present in rat brain cortex slices, each with its own specificity with regard to substrate and with regard to amino acids which produce inhibitory effects. The nature of these inhibitory effects may be either direct (competition for a limiting number of sites) or indirect (as they are when glutamate or aspartate cause a decrease in the ATP content).Comparison of the specificities of the glycine transport systems present in rat brain cortex slices and in Ehrlich ascites carcinoma cells indicates that these two systems have little in common and the relation of this finding to the structural requirements necessary for chemotherapeutic activity is discussed.

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