Characterization of Corticosterone‐Induced Protein Synthesis in Hippocampal Slices

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Abstract
Corticosterone significantly increases the incorporation of [3H]leucine into specific cytosol protein(s) isolated from in vitro hippocampal slices prepared from adult male albino rats. In slices coincubated with glucocorticoid plus a protein synthesis inhibitor (1 mM-cycloheximide), no such enhancement of amino acid incorporation was observed; apparently the hormone acts in the hippocampus to increase de novo protein synthesis. The steroid-induced protein synthesis was first detectable (+5.7%) following a 30 min exposure of slices to corticosterone; slices incubated for 1 or 2 h both showed a 12% increase in synthesis of the affected protein(s) when compared with controls. To determine whether the glucocorticoid alteration of protein metabolism was receptor-mediated, hippocampal slices were also incubated with 10 nM progesterone, a steroid known to compete for corticosterone binding to its cytosol receptor. Progesterone alone, which does not translocate cytoplasmic receptors to the nucleus, did not alter hippocampal protein metabolism and effectively blocked the induction by corticosterone of the 54K protein(s). In the rat hippocampus corticosterone apparently interacts with high-affinity steroid receptors to regulate the synthesis of specific protein(s).