The uptake of glutamic acid and glutamine by brain and other tissues of the rat and mouse.

Recently we reported studies of the absorption of glutamic acid and glutamine from the gut of the cat by analysis of the portal blood, and of the concentration changes of the two amino acids in the peripheral blood plasma after oral administration of glutamic acid to human subjects (3). In a further study of the fate of glutamic acid and glutamine in the animal body, the uptake of the two amino acids by brain, muscle, liver, and kidney after intravenous administration to rats and mice has now been determined. Changes in total amino acid nitrogen have been estimated previously in brain and other tissues (4, 5) after the intravenous administration of glutamic acid to rats and dogs, but this unspecific measure of amino acid concentration cannot give evidence regarding the movement of particular amino acids, especially since it has been found that a high blood level of glutamic acid causes an increased uptake of other amino acids by the tissues (3, 6).