The effect of corticosteroids on amino acid content of brain tissue preparations.

Abstract (1) We studied the effect of hormones on amino acid uptake and metabolism in incubated mouse brain slices, a model for studying effects on brain cells. (2) Only a few of the hormones—hydrocortisone, estradiol and progesterone—had effects, and only at low amino acid concentrations in the medium. Some hormones that are active in other tissues, such as insulin and glucagon, were without effect. (3) Amino acid uptake was stimulated by the three corticoid hormones tried; estradiol at higher concentrations caused a release of amino acids from the tissue into the medium but the others did not. (4) Because the changes in tissue levels of γ-aminobutyric acid (GABA) were especially large, we measured the metabolism of GABA. The formation of GABA was not greatly altered; its further metabolism, most likely via GABA aminotransferase, was inhibited. (5) We conclude that corticosteroids, at high levels, could affect the distribution of some cerebral amino acids, primarily by affecting their metabolism; it is the inhibition of metabolism that results in increased retention of GABA.