title: Regional adrenal blood flow responses to adrenocorticotropic hormone after chronic embolization of the fetal placental circulation in sheep.
abstract: To ascertain whether repeated hypoxic stress would alter the response of the adrenal cortex to adrenocorticotropic hormone (ACTH), by premature activation of the hypothalamic-pituitary-adrenal axis, we studied fetal sheep subjected to daily reduction of arterial oxygen content by embolization of the fetal placental circulation with 15 microns microspheres for 8 days from about day 124 of gestation (term approximately 147 days) and sham-embolized controls. Starting before the final embolization (or sham-embolization) on day 8, and continuing for 24 h, the fetus was given an intravenous infusion of ACTH1-24 (0.5 microgram/h) or vehicle. Fetal and maternal blood samples were taken for determination of immunoreactive cortisol, and regional adrenal and fetal placental blood flows were measured by the microsphere technique at three time points: 1 h before infusion, 3 h after the start of the infusion (1 h after embolization), and after 24 h of infusion. Prior to infusion of ACTH or vehicle, fetal placental blood flow was lower in microsphere-embolized fetuses than in sham-embolized controls (199 +/ 15 vs 292 +/- 25 ml/min per 100 g tissue; mean +/- S.E.; P<0.01). However, plasma cortisol and adrenal cortical blood flow did not differ between embolized fetuses and controls. Adrenal vascular responses to the 24-h infusion of ACTH were similar in embolized and sham-embolized fetuses. Adrenal cortical blood flow increased 3-fold (P<0.05) due to decreased vascular resistance (P<0.01), with no change in adrenal medullary blood flow. Thus, while daily embolization of the fetal placental circulation caused a sustained decrease in cotyledonary blood flow, no evidence of altered responsiveness of the adrenal cortex to ACTH was found in these experiments.
authors.affiliation: Department of Physiology, University of Odense, Denmark.
authors.forename: A M
authors.initials: AM
authors.lastname: Carter
authors.forename: J R
authors.initials: JR
authors.lastname: Challis
authors.forename: P
authors.initials: P
authors.lastname: Svendsen
mesh_terms: D000311:Adrenal Glands / Q000098:blood supply* / Q000196:embryology; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005311:Fetal Hypoxia / Q000503:physiopathology*; D006854:Hydrocortisone / Q000097:blood; D008863:Microspheres; D010920:Placenta / Q000098:blood supply; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D012756:Sheep
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone