title: Do plasma ACTH and cortisol concentrations in the late-gestation fetal sheep vary diurnally?
abstract: This study tested the hypothesis that fetal plasma ACTH and cortisol concentrations vary diurnally, and the mean concentration and the amplitude of the rhythm vary as a function of fetal gestational age. Nine chronically-catheterized fetal sheep were studied between 120 and 142 days' gestation. All of the fetuses were born spontaneously and alive. The pregnant ewes were maintained in a room with a regular light cycle (on at 07.30, off at 17.30). Food and water were available ad libitum. Blood samples were drawn at 4-h intervals throughout a 24-h period. There were no significant daily variations in fetal plasma ACTH, cortisol, or progesterone concentrations, except in the last 3 days of fetal life. In these fetuses ACTH and cortisol concentrations were increased in the afternoon and evening. We conclude that there is no diurnal rhythm in ovine fetal hypothalamo-pituitary-adrenal axis activity, and that the increased plasma concentrations of ACTH and cortisol in the afternoon and evening hours of the last few days of fetal life might be a response to increased uterine contraction activity.
authors.affiliation: Department of Physiology, University of Florida College of Medicine, Gainesville 32610-0274.
authors.forename: M E
authors.initials: ME
authors.lastname: Bell
authors.forename: C E
authors.initials: CE
authors.lastname: Wood
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D005865:Gestational Age; D006854:Hydrocortisone / Q000097:blood*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012756:Sheep
chemical_list: D011374:Progesterone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone