Hormonal and biophysical responses to acute hypoxemia in fetal sheep at 0.7–0.8 gestation

Abstract

We examined whether there was a minimal change in fetal arterial [Formula: see text] necessary to elicit alterations in plasma adrenocorticotropic hormone, arginine vasopressin, or cortisol or to affect the incidence of breathing movements or eye movements in fetal sheep at 106–117 days of gestation. Fetal sheep were exposed to two levels of hypoxemia, mild (4.1 mmHg [Formula: see text] drop) (1 mmHg = 133.32 Pa) and moderate (8.4 mmHg [Formula: see text] drop), for 1 h without acidemia. Hypoxemia was induced by altering the inspired percent oxygen of the mother. No significant hormonal and biophysical changes were observed in mild hypoxemia. In moderate hypoxemia, there were significant increases of fetal adrenocorticotropic hormone and arginine vasopressin and decreased incidence of fetal breathing movements. However, there were no significant changes in cortisol or eye movements. We conclude that a fetal arterial [Formula: see text] drop of between 4.1 and 8.4 mmHg is necessary to elicit responses to hypoxemia in fetal sheep at 106–117 days of gestation in adrenocorticotropic hormone, arginine vasopressin, and fetal breathing movements, but this degree of hypoxemia does not cause changes in cortisol or fetal eye movements.Key words: fetal sheep, hypoxemia, adrenocorticotropic hormone, arginine vasopressin, cortisol, fetal breathing movements, fetal eye movements.