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This Article Full Text Full Text (PDF) All Versions of this Article: 90/4/545    most recent expphysiol.2005.030320v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Roelfsema, V. Articles by Bennet, L. Search for Related Content PubMed PubMed Citation Articles by Roelfsema, V. Articles by Bennet, L. Related Collections Neuroendocrinology/Endocrinology

Departments of ¹ Physiology² Paediatrics³ The Liggins Institute, The University of Auckland, Auckland, New Zealand

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.

(Received 20 February 2005; accepted after revision 4 March 2005; first published online 8 March 2005)
Corresponding author L. Bennet: Department of Physiology, Faculty of Medicine and Health Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand. Email: l.bennet{at}auckland.ac.nz

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