The adrenocortical activity of male Wistar rats during and following the administration of glucocorticoid was studied and compared wtih that of hypophysectomized rats. An experiment was also undertaken to determine whether or not glucocorticoid has any effect on the steroidogenesis at the adrenal level.
1) The subcutaneous administration of prednisolone produced a rapid reduction in plasma corticosterone, a less rapid reduction in adrenal corticosterone, and a gradual decrease in adrenal weight. Following a 20-day treatment, the adrenocortical activity became almost normal 7 days after withdrawal. The response of plasma and adrenal corticosterone to ACTH was suppressed significantly after a 2-day treatment, while the base-line level was still within normal range, but recovered to normal 7 days after the cessation of the treatment.
2) In hypophysectomized rats, the reduction in plasma and adrenal corticosterone and in adrenal weight was more rapid than in prednisolone treated rats. Although there were many resemblances in the adrenal histology of these two conditions, a distinct difference was observed. The lipid granules in the zona fasciculata were abundant until 30 days after hypophysectomy, while they were reduced soon after the beginning of prednisolone treatment.
3) The administration of prednisolone in hypophysectomized rats did not significantly affect the adrenal histology, nor the plasma and adrenal corticosterone. On the other hand, nor-androstenolone phenylpropionate, a potent androgen, caused a partial repair of the atrophied adrenal cortex after hypophysectomy, although it had no effect on the plasma and adrenal corticosterone. These findings led to the conclusion that the main difference in the adrenal histology of hypophysectomized rats and prednisolone treated rats could not be attributed to the direct action of prednisolone on the adrenal cortex.
4) The administration of prednisolone failed to affect the plasma and adrenal corticosterone and their response to ACTH in hypophysectomized rats. It may be concluded that glucocorticoids do not significantly inhibit the steroidogenesis at the adrenal level insofar as the usual dosage is concerned.
The comparative effects of cortisone, prednisolone, triamcinolone, dexamethasone and DOCA on the adrenal cortex and other organs of albino rats were studied.
1) Every glucocorticoid used produced a marked reduction in plasma and adrenal corticosterone as well as in adrenal weight. Histological examination of the adrenal gland revealed that the zona fasciculata had atrophied and was depleted in lipid content, while the zona glomerulosa had broadened and was rich in lipid granules. In the pituitary gland, glucocorticoids caused degranulation in basophils, a slight increase in the percentage of basophils and a slight decrease in acidophils.
Involution of the thymus, atrophy of the lymph follicles in the spleen, fatty degeneration of the liver and hyperplasia of the Langerhans' islets were observed in all glucocorticoid treated rats. Degeneration of the thyroid epithelium and hypoplasia of the prostate were seen in some of the rats treated with prednisolone and dexamethasone.
DOCA caused a slight but significant reduction in plasma corticosterone and adrenal weight. Histologically, the zona glomerulosa had atrophied and was diminished in lipid content, while the zona fascieulata appeared to be normal.
2) The relative potencies of cortisone, prednisolone, triamcinolone and dexamethasone to deposit liver glycogen, to inhibit granuloma formation and to suppress adrenocortical activity were studied. The ability of a given glucocorticoid to suppress adrenocortical activity does not parallel its liver glycogen deposition activity, but seems to parallel its anti-inflammatory activity.
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