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

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 (22)Na(+) 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 Ca(2+) 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 Ca(2+) in media after these additions indicate that Na(+) entry is sometimes associated with low Ca(2+) concentration, but that other substances, especially l-glutamate, act without greatly diminishing Ca(2+) concentration. 4. Experiments with 2,4-dinitrophenol and valinomycin are also reported and aspects of the Na(+) entry formulated and discussed.