REGULATION OF ADRENOCORTICOTROPIN SECRETION IN-VITRO BY ANTERIOR-PITUITARY CORTICOTROPHS FROM FALLOW DEER (DAMA-DAMA)

The actions of corticotropin-releasing hormone (CRH), vasopressin (VP) , the synthetic glucocorticoid dexamethasone (DEX), and mifepristone ( RU 486), a glucocorticoid antagonist, on the secretion of adrenocortic otropin (ACTH) by cultured fallow deer corticotrophs were studied in v itro. On Day 5 of primary culture, corticotrophs were challenged for u p to 4 hr with medium alone (Control), CRH, VP, DEX, forskolin (FSK), phorbol ester (TPA), cyclic AMP (cAMP), and/or RU 486 at various conce ntrations and combinations. CRH, VP, FSK and TPA each stimulated (P < 0.01) the secretion of ACTH in dose- and time-related manners. Relativ e to Control, CRH at 0.001 and 0.1 mu M and VP at 0.01 and 1 mu M incr eased (P < 0.01) medium concentration of ACTH by 7.3-, 13.5-, 3.7- and 9.0-fold, respectively. There was a treatment x incubation time inter action (P < 0.01) such that at 30-min posttreatment, CRH-induced ACTH secretion tended (P < 0.10) to be less than that obtained via VP treat ment, whereas at 1, 3, and 4 hr posttreatment, medium concentration of ACTH from cells treated with 0.1 mu M CRH was greater (P < 0.05) than that in cells treated with 1 mu M VP. At equimolar doses of 0.01 and 0.1 mu M, CRH was 3.4- and 3.0-fold more potent (treatment x dose, P < 0.05) than VP. Cotreatment with 1 mu M DEX reduced (P < 0.001) the st imulatory effects of CRH (0.1 mu M), VP (1 mu M), FSK (10 mu M), TPA ( 0.1 mu M), and cAMP (0.001 M). However, the coaddition of RU 486 (1 mu M) to the CRH plus DEX- and the FSK plus DEX-treated wells partially negated the inhibitory effects of DEX. RU 486 completely negated the i nhibitory effects of DEX on the VP-, TPA-, and cAMP-stimulated secreti on of ACTH. These data indicate that CRH is a more potent stimulator o f ACTH secretion than is VP in primary culture of fallow deer pituitar y cells. This study also demonstrates the utility of an in vitro cultu re system to investigate stress-related hormonal interactions in cervi ds.