TRANSPORT OF TRYPTOPHAN AND TYROSINE IN RAT-BRAIN SLICES IN THE PRESENCE OF LITHIUM

Slices from rat cerebral cortex, brain stem, and cerebellum were incubated in media in which 1, 10, or 100 mmol/liter NaCl had been replaced by equimolar amounts of LiCl. The initial influx fo tryptophan and tyrosine into the slices diminished in the lithium-containing media. The lithium-induced inhibition was not competitive. The equilibrium accumulation of the amino acids was also less in the presence of LiCl. The incorporation of tryptophan and tyrosine into the proteins of the slices was inhibited by lithium. There were no clear differences between the brain areas studied. It has been suggested earlier that a lithium treatment enhances thesin vivo cerebral uptake of these aromatic amino acids. The present results show that such a possible increase in uptake is not a direct effect of lithium ions on cell membranes. © 1979 Plenum Publishing Corporation.