title: Maturation of cortisol responses to adrenocorticotropic hormone in twin fetal sheep in vivo.
abstract: OBJECTIVE
  Adrenal steroidogenesis is important for maturation of fetal organ systems and plays a role in triggering parturition in ovine pregnancies. Studies have suggested a differential increase in baseline cortisol between twin gestations near term. Our aim was to further delineate the mechanisms responsible for the differences between the hypothalamic-pituitary-adrenal axes of twin fetuses in vivo.
  
  
  METHODS
  Surgery was performed on pregnant ewes (n = 6) with twin gestations to implant fetal vascular catheters. After recovery but while the subjects were resting, plasma cortisol concentrations were similar in both fetuses. Fetuses received, intravenously, boluses of adrenocorticotropic hormone at 2 doses, and plasma samples were obtained for analysis of the cortisol response. This stimulation by adrenocorticotropic hormone was then repeated in the same fetuses approximately 4 days later, after the increase of resting daily cortisol values in one but not the other fetus.
  
  
  RESULTS
  Cortisol responses to adrenocorticotropic hormone before changes in daily resting cortisol concentrations were indistinguishable between twins. However, after separation of daily resting cortisol values, fetuses in group A (elevated resting cortisol concentration) demonstrated a significantly increased response to stimulation by adrenocorticotropic hormone.
  
  
  CONCLUSIONS
  These results suggest a differential development in response to stimulation by adrenocorticotropic hormone between twin fetuses in vivo as the mechanism responsible for the asynchronous elevation of one twin's resting plasma cortisol concentration.
authors.affiliation: Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Block
authors.forename: M L
authors.initials: ML
authors.lastname: Draper
authors.forename: J C
authors.initials: JC
authors.lastname: Rose
authors.forename: J
authors.initials: J
authors.lastname: Schwartz
mesh_terms: D000311:Adrenal Glands / Q000196:embryology*; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D005314:Embryonic and Fetal Development; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood*; D007700:Kinetics; D011247:Pregnancy; D012756:Sheep; D014427:Twins
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone