The effects of metabolic inhibitors on amino acid uptake and the levelsof ATP, Na +, and K + in incubated slices of mouse brain

Abstract

(1) The effect of various metabolic inhibitors on the uptake of amino acids and on the levels of ATP, Na +, and K + were compared in incubated slices of mouse brain. With increasing concentration of the inhibitors, uptake, ATP, and K + decreased, and Na + increased. (2) The degree of changes of ATP and of ions was parallel. There were some exceptions: cyanide affected ATP and K + more than Na +, and ouabain affected the ions more than ATP. In most cases the decrease of K + was accompanied by an equimolar increase in Na +. Fluoride inhibited aspartate and glutamate uptake less than that of the other amino acids. (3) The amino acids had no effect on Na + or K + levels, but the presence of glutamate and aspartate usually resulted in the further decrease in ATP. (4) ATP can be lowered from levels similar to those present in vivo to less than 1% of that, but a small uphill (concentrative) amino acid uptake remains. A small (5–20%) decrease in ATP had no significant effect on uptake. (5) There were differences in the degree of decrease of ATP and of amino acid uptake. ATP was lowered much more than uptake by iodoacetate, also to some degree by cyanide, but fluoride lowered uptake more than ATP. These results further support the concept that the level of ATP is not the main control of metabolite transport in the brain. (6) The relative potency of the various inhibitors (30% inhibition of amino acid uptake) varied. Rotenone at 5 n M was most effective, > valinomycin > oligomycin > ouabain > gramicidin-D > dinitrophenol > iodoacetate > iodosobenzoate > cyanide > amytal > fluoride > fluoroacetate (at 1.5 m M) .