EFFECTS OF EXOGENOUS ADRENOCORTICOTROPIC HORMONE (ACTH) UPON PITUITARY ACTH CONCENTRATION AFTER PROLONGED CORTISONE TREATMENT AND STRESS*

Abstract

Pituitary adrenocorticotropic hormone (ACTH), measured by an in vitro steroidogenic technique, is significantly depleted following chronic administration of cortisone in the rat. Persistence of adrenal atrophy despite partial repletion of pituitary ACTH levels 10 days after cessation of treatment suggests that ACTH release during this period is negligible and that newly-synthesized ACTH is stored rather than secreted. The steroid-induced depletion of pituitary ACTH concentration is neither prevented nor ameliorated by the addition of ACTH in a variety of dosage schedules. Adjunctive ACTH administration does not modify the striking reduction in ACTH release after stress which occurs in the cortisone-treated animal. Adrenal atrophy following steroid treatment can be prevented or repaired by the administration of ACTH.