PROSTAGLANDIN-E2 ENHANCES AVP-STIMULATED BUT NOT CRF-STIMULATED ACTH-SECRETION FROM CULTURED FETAL SHEEP PITUITARY-CELLS

This study examined the ability of prostaglandin E2 (PGE2) to regulate ACTH secretion from cultured anterior pituitary cells of fetal sheep between days 130 and 140 of gestation (term = 145 days). Corticotrophin-releasing factor (CRF) and arginine vasopressin (AVP) induced dose-dependent (0.1-1000 nmol/l) increases in ACTH secretion from fetal sheep pituitary cells maintained in culture for 6 days, with AVP being significantly (P < 0.01) more potent than CRF. PGE2 (1000 nmol/l) significantly (P < 0.05) enhanced the ability of AVP, but not CRF, to stimulate ACTH secretion. However, PGE2 given alone (0.1-1000 nmol/l) had no effect on ACTH secretion. Concomitant administration of CRF and AVP induced a greater release of ACTH than after treatment with either peptide alone, a synergistic interaction which was unaffected by simultaneous administration of PGE2. These results provide evidence for a direct action of PGE2 on ACTH secretion from the fetal sheep pituitary gland via a specific interaction with AVP. This interaction may allow increased fetal plasma concentrations of PGE2, seen during late gestation, to stimulate fetal pituitary-adrenal maturation.