Cortisol and ACTH responses to severe asphyxia in preterm fetal sheep.
It has been hypothesized that the hypothalamic-pituitary-adrenal (HPA) axis is immature in the preterm fetus and that this compromises their ability to adapt to hypoxic stress; however, there are few direct data. We therefore examined the effects of asphyxia on HPA responses in chronically instrumented preterm fetal sheep (104 days of gestation; term is 147 days), allocated to a sham control group (n = 7) or 25 min of complete umbilical cord occlusion (n = 8), followed by recovery for 72 h. During umbilical cord occlusion there was a rapid rise in ACTH levels (230.4 +/- 63.5 versus 14.1 +/- 1.8 ng ml(-1) in sham controls, 16-fold) and cortisol levels (7.4 +/- 4.9 versus 0.2 +/- 0.1 ng ml(-1), 31-fold), with further increases after release of cord occlusion. ACTH levels were normalized by 24 h, while plasma cortisol levels returned to sham control values 72 h after asphyxia. Fetal arterial blood pressure was elevated in the first 36 h, with a marked increase in femoral vascular resistance, and correlated positively with cortisol levels after asphyxia (P = 0.05). In conclusion, the preterm fetus shows a brisk, substantial HPA response to severe hypoxia.
Roelfsema
Vincent
V
Department of Physiology, Faculty of Medicine and Health Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Gunn
Alistair J
AJ
Fraser
Mhoyra
M
Quaedackers
Josine S
JS
Bennet
Laura
L
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001237:Asphyxia / Q000378:metabolism*; D001784:Blood Gas Analysis; D001786:Blood Glucose / Q000378:metabolism; D005260:Female; D005312:Fetal Blood / Q000737:chemistry / Q000378:metabolism; D005333:Fetus / Q000098:blood supply / Q000378:metabolism*; D005865:Gestational Age; D006854:Hydrocortisone / Q000378:metabolism*; D019344:Lactic Acid / Q000097:blood; D011247:Pregnancy; D012039:Regional Blood Flow / Q000502:physiology; D012756:Sheep; D013116:Spinal Cord / Q000502:physiology; D014470:Umbilical Cord / Q000502:physiology
D001786:Blood Glucose; D019344:Lactic Acid; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone