No abstract

Summary Both the circadian and stress‐induced changes in plasma corticosterone concentration were abolished by the inclusion of betamethasone in the drinking water of rats. Adrenal sensitivity to exogenous corticotrophin (ACTH) was unimpaired by the betamethasone treatment. The normal circadian rhythm in plasma corticosterone returned within 1 day of withdrawal of the steroid, but the response to stress was normal only after 3 days. The possible significance of these observations is discussed.

Summary1. Betamethasone caused growth retardation, adrenal atrophy and impaired hypothalamo-pituitary-adrenal (HPA) activity in the rat. 2. In spite of the profound impairment, recovery of normal HPA function was rapid, but the growth retardation persisted.3. The ability of the pituitary gland to secrete basal corticotrophin (ACTH), recovered more rapidly and the adrenocorticotrophic response to stress less rapidly than the ability of the adrenal cortex to respond to ACTH. 4. The degree of HPA suppression was not determined by the total dose of steroid. 5. The possible significance of the results is discussed.

Summary1. The functional integrity of the hypothalamo-pituitary adrenal (HPA) system was assessed in rats after prolonged treatment with tetracosactrin. 2. Adrenal size and sensitivity to corticotrophin were increased. 3. Both the circadian rhythm and the stress-induced increase in HPA activity were inhibited. The circadian rhythm recovered before the response to stress. 4. Tetracosactrin given after betamethasone treatment delayed the return of a normal HPA response to stress. 5. Suppression of HPA activity appeared to be the result of a direct action of tetracosactrin and not entirely due to the elevations in the plasma corticosterone concentration which it caused.

No abstract

Summary1. Production of corticosterone in vitro was studied using adrenal glands from rats which had been subjected to stress or treated with betamethasone.2. An increase in corticosterone production occurred in the first but not the second hour of incubation in adrenals removed immediately after stress. When the interval between stress and adrenalectomy was longer, the increased corticosterone production persisted. 3. Betamethasone had no effect on corticosteroidogenesis in vitro when added directly to the incubation medium or when administered to rats shortly before removal of their adrenal glands. 4. Corticosteroidogenesis in vitro was considerably reduced in the adrenals of rats given prolonged treatment with betamethasone. 5. The significance of the results and the reliability of in vitro corticosteroid production as an index of hypothalamo-pituitary-adrenal activity is discussed.

No abstract

No abstract