Stress-induced heat shock protein 70 expression in adrenal cortex: an adrenocorticotropic hormone-sensitive, age-dependent response.

The induction of heat shock proteins (HSP) by cellular stress and the activation of the hypothalamic-pituitary-adrenal axis by physiologic stress are biological responses that aid in the maintenance of cellular and organismal homeostasis, respectively. In this report, restraint stress, known to activate the hypothalamic-pituitary-adrenal axis, is shown to induce expression of HSP70 mRNA selectively in the adrenal cortex of the rat. Restraint-induced HSP70 expression in the adrenals is rapid and is preceded by the activation of a protein factor capable of binding to the heat shock transcriptional control element. The ability of restraint to induce HSP70 expression in the adrenal is virtually eliminated in hypophysectomized rats but can be restored by the exogenous administration of adrenocorticotropic hormone. The magnitude of this induction declines as a function of increasing age, which may contribute to a reduced stress tolerance by aged animals. These results support a role for HSP70 in the physiologic stress response mediated by the hypothalamic-pituitary-adrenal axis.