Features of the functioning of the hypothalamic-pituitary-adrenal system during aging in female monkeys

Abstract

The adrenocortical function has been studied in Macaca mulatto of different age: 6-9 years (young adult, n=5) and 20-26 years old, n=5). Corticosteroids (hydrocortisone and dihydroepiandrosterone sulfate DEAS) were measured by radioimmunoassay and enzyme immunoassay under basal conditions, during acute stress (insulin-induced hypoglycemia and 2-hour immobilization), and after dexamethasone injection.

The basal hydrocortisone levels were virtually the same in both groups, while the concentration of DEAS dropped in old animals. The reaction of the adrenal cortex to immobilization was decreased in old monkeys, which manifested by delayed peak values of both hydrocortisone and DEAS and a lesser area of their response for the examined 4-hour period. Dexamethasone test detected in monkeys aged 20-26years the development of relative resistance of the hypothalamo-pituitary-adrenal system to the overwhelming majority of glucocorticoids by the feedback mechanism. The feedback impairment in the regulation of the adrenocortical function may be at least partially mediated by the formation of a steroid imbalance in the peripheral blood during aging, primarily by a decrease in DEA (DEAS).