ASSAY OF CORTICOTROPHIN PREDNISOLONE PRETREATMENT INSTEAD OF HYPOPHYSECTOMY IN THE ADRENAL ASCORBIC ACID DEPLETION TEST

Abstract

The inhibitory effect of various corticosteroids and synthetic analogues on the stress-induced release of corticotrophin was measured in adult male rats by means of the adrenal ascorbic acid depletion test. All the compounds examined were active, dexamethasone and prednisolone being the most effective inhibitors. A single subcutaneous injection of a microcrystalline aqueous suspension of prednisolone (1.5 mg per rat), given about 2 hours before left-sided adrenalectomy, blocked completely the adrenal ascorbic acid depletion. Quantitative assays of a purified corticotrophin preparation were carried out with hypophysectomized and prednisolone-treated intact rats. The latter were less sensitive to corticotrophin, but the slopes of the calibration curves and the standard deviations appeared to be the same in both instances. It is concluded that it is feasible to replace the surgical hypophysectomy by prednisolone pretreatment in the ascorbic acid depletion test for corticotrophin.