Stress-induced regulation of glucocorticoid receptor gene expression in the rat

To investigate the mechanism of the changes in glucocorticoid receptor (GR) under various stress conditions, experiments were carried out on normal and partial adrenalectomized rats by utilizing radioligand binding assay and molecular hybridization. It was found that hepatic GR binding capacity and GR mRNA in intact rats decreased significantly after the scalding stress, but the changes in GR binding capacity is mainly owing to the decrease in GR mRNA levels, and other mechanisms at protein level are also involved. In partial adrenalectomized rats, hepatic GR binding capacity and GR mRNA were increased instead of decreased, whereas serum corticosterone did not rise in response to the scalding stress. Therefore, it may be concluded that the decrease in GR binding capacity and GR mRNA in intact rats after the scalding stress is mainly the result of the increased concentration of serum corticosterone. Our further studies did demonstrate that there exists downregulation of GR mRNA in rats by exogenous administration of hydrocortisone. It is also suggested that there might be factors that can upregulate GR and GR mRNA in intact rats after the scalding stress.