Hypophyseotropic regulation of adenohypophyseal adrenocorticotropin secretion.

Regulation of anterior pituitary secretion of adrenocorticotropin (ACTH) is a complex process subserved by multiple hypophyseotropic factors. The nature of participation (dynamic or permissive) and relative significance of each factor in mediation of stimulus-induced ACTH secretory events have not been elucidated. Attempts were made to directly define the contributions of corticotropin-releasing factor (CRF), arginine vasopressin, oxytocin, and epinephrine to ACTH secretion elicited by hemodynamic and hypoglycemic stimuli in anesthetized rats. The observations support the following hypotheses: 1) CRF represents the predominant regulatory factor in mediation of the stimulus-induced ACTH-secretory responses studied, 2) hypophyseotropic coding of ACTH secretion is stimulus-dependent and involves factors in addition to CRF, and 3) CRF participates in mediation of ACTH secretion in either a dynamic or a permissive fashion depending on the nature of the secretory stimulus. Finally, the potential for central interactions among these regulatory factors is significant and underscores the complexity of this regulatory system at all levels of organization.