title: Effect of cortisol infusion on the pituitary-adrenal axis of the hypothalamo-pituitary-disconnected fetal sheep.
abstract: In order to determine whether cortisol acts directly at the level of the fetal pituitary to promote pars distalis corticotroph maturation, we have infused cortisol into the hypothalamo-pituitary-disconnected (HPD) fetal sheep from 111 to 117 days of gestation. In this study we have measured fetal plasma cortisol and immunoreactive adrenocorticotrophic hormone (ir-ACTH) concentrations between 105 and 116 days of gestation, and we have determined the proportions of adult- and fetal-type corticotrophs in the pars distalis of catheter control fetuses and in HPD fetuses infused with either saline (HPD+SAL) or cortisol (2 mg/day; HPD+F). The fetal plasma cortisol concentrations did not change significantly following HPD. The mean fetal plasma cortisol concentration between 113 and 116 days was threefold higher in the HPD+F fetuses than that measured in HPD fetuses. Following HPD, fetal plasma ir-ACTH concentrations were significantly higher than in catheter control fetuses. Despite the significant elevation in plasma cortisol concentrations in HPD+F fetuses between 113 and 116 days, plasma ir-ACTH concentrations were not different in these fetuses from HPD fetuses infused with saline. At 117 days of gestation in HPD+F fetuses, the proportion of fetal-type corticotrophs in the pars distalis was significantly less than in the HPD+SAL fetuses; however, there was no significant change in the proportion of adult-type corticotrophs in the pars distalis following cortisol infusion. We have shown that cortisol has a direct trophic effect on the maturation of the pars distalis corticotrophs; however, the full maturation of these cells requires an intact hypothalamo-pituitary axis. These findings demonstrate the importance of the fetal hypothalamus in anterior pituitary corticotroph maturation during the last third of gestation.
authors.affiliation: Department of Anatomy, University of Melbourne, Parkville, Vic., Australia.
authors.forename: G C
authors.initials: GC
authors.lastname: Antolovich
authors.forename: I C
authors.initials: IC
authors.lastname: McMillen
authors.forename: P M
authors.initials: PM
authors.lastname: Robinson
authors.forename: M
authors.initials: M
authors.lastname: Silver
authors.forename: I R
authors.initials: IR
authors.lastname: Young
authors.forename: R A
authors.initials: RA
authors.lastname: Perry
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D006854:Hydrocortisone / Q000008:administration & dosage* / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000196:embryology / Q000502:physiology*; D007262:Infusions, Intravenous; D010902:Pituitary Gland / Q000196:embryology / Q000473:pathology; D010913:Pituitary-Adrenal System / Q000187:drug effects* / Q000196:embryology; D011247:Pregnancy; D011256:Pregnancy Outcome; D011863:Radioimmunoassay; D012756:Sheep
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone