Synergistical effects of ovine corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) on the release of pro-opiomelanocortin (POMC) related peptides by pituitary adenoma of a patient with Nelson's syndrome in vitro

Abstract

The effects of synthetic ovine corticotropin-releasing factor (oCRF), arginine vasopressin (AVP), alpha-melanocortin (alpha MSH), and dexamethasone on the release of pro-opiomelanocortin (POMC)-related peptides were studied on a pituitary adenoma of a patient with Nelson's syndrome. CRF, at doses up to 100 ng/ml, has no effect on IR-ACTH, IR-hNT or IR-beta LPH secretion by the pituitary adenoma cells within the first week of monolayer culture. During the second week of in vitro conditions, however, the cells responded to oCRF (1-100 ng/ml) with a significant increase in all three POMC-related peptides. AVP (10 and 100 ng/ml) was effective in stimulating secretion of the three POMC-related peptides on day 6 in vitro; in addition, during the second week in culture, AVP (1 ng/ml) acted synergistically with 1-100 ng/ml of oCRF to release IR-ACTH, IR-hNT and IR-beta LPH at least 3-4 fold higher than CRF alone. alpha MSH (10 micrograms/ml) and dexamethasone (10(-6)M) did not alter the release of any of the three peptides. These results demonstrate that CRF and AVP can act synergistically on human pituitary tissue in vitro to promote the release of POMC-related peptides and also in vivo as shown by others.