Glutamate, calcium ion-chelating agents and the sodium and potassium ion contents of tissues from the brain

[摘要]

1. Salts of l-glutamate added to cerebral tissues maintained in glucose–saline–bicarbonate solutions cause the Na⁺ content of the tissues to increase rapidly and K⁺ to be lost. Entry of ²²Na⁺ also is accelerated by l-glutamate and this acceleration is inhibited by low concentrations of tetrodotoxin. 2. Tissue Na⁺ content and its rate of increase after the addition of l-glutamate are affected by the Ca²⁺ of incubation media. 3. Very rapid and extensive entry of Na⁺ to the tissue is caused by EDTA, and a moderate entry by citrate and ATP. Calculations of the concentration of free Ca²⁺ in media after these additions indicate that Na⁺ entry is sometimes associated with low Ca²⁺ concentration, but that other substances, especially l-glutamate, act without greatly diminishing Ca²⁺ concentration. 4. Experiments with 2,4-dinitrophenol and valinomycin are also reported and aspects of the Na⁺ entry formulated and discussed.