Functional stimulation of natural killer cells by corticotropin-releasing factor

Abstract

The corticotropin-releasing factor (CRF) analog CRF 9-41 inhibits CRF, but not forskolin or dibutyryl cyclic AMP, stimulated release of ACTH from isolated pituitary cells. CRF 9-41 also blocks CRF-stimulated accumulation of cyclic AMP in a parallel dose dependent fashion. CRF 9-41 has no effect on basal ACTH release or cAMP levels. This substantiates that the analog acts as a direct CRF antagonist and that the site of this inhibition is most likely at the level of binding of CRF to its receptor on the corticotrope. Various substances, including most prominently glucocorticoids, inhibit release of ACTH from the pituitary (1,2). In an effort to develop another class of inhibitors, Rivier et al (3) recently synthesized analogs of corticotropin releasing factor (CRF). One among these, alpha-helical ovine CRF 9-41 blunts adrenalectomy and stress induced ACTH release in non-anesthetized rats (3,4). At micromolar concentrations, CRF 9-41, shifts rightward the dose response of isolated pituitary cells to ovine CRF (3). Thus, the authors suggested that CRF 9-41 acts as a competitive antagonist to CRF-induced ACTH secretion. CRF appears to act through stimulation of adenylate cyclase (5–7). To determine the potential site of action of CRF 9-41 in the activation sequence for adenylate cyclase, we studied its effects on pituitary cyclic AMP formation and ACTH secretion from dispersed anterior pituitary cells derived from normal adult rats, as well as, its interaction with cyclic nucleotide agonists.