Effect of pulsatile oxytocin administration to the pregnant ewe in the last third of gestation on fetal ACTH and cortisol response to acute hypoxemia.
OBJECTIVE
The aim of this study was to examine the effect of increased myometrial contractility throughout the last third of pregnancy on the ovine fetal response to short-term hypoxemia.


METHODS
Oxytocin (600 microU/kg/minute, n = 5) or saline (n = 7) was infused for 5 minutes every 20 minutes into the maternal jugular vein starting at 95-99 days of gestation and continuing throughout the last third of gestation. Fetuses were subjected to a hypoxemic challenge (1 hour) at 131 days of gestation while fetal plasma ACTH and cortisol levels and nuchal muscle electromyogram activity were monitored.


RESULTS
The fetal plasma ACTH concentration before and during the hypoxemic challenge was similar in the control and oxytocin groups. The fetal plasma cortisol concentration in the oxytocin group was significantly lower before and during the hypoxemia than in the controls. During hypoxemia, fetal nuchal muscle activity was significantly reduced only in the control group.


CONCLUSIONS
Increased myometrial contracture frequency throughout the last third of pregnancy alters both the neuroendocrine and behavioral responses of fetal sheep to short-term hypoxemia.
Owiny
J R
JR
Laboratory for Pregnancy and Newborn Research, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA.
Jenkins
S L
SL
Sadowsky
D W
DW
Nathanielsz
P W
PW
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism*; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D004576:Electromyography; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D005865:Gestational Age; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000196:embryology* / Q000503:physiopathology; D007262:Infusions, Intravenous; D008431:Maternal-Fetal Exchange; D009215:Myometrium / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D010313:Partial Pressure; D011247:Pregnancy; D012756:Sheep; D014590:Uterine Contraction / Q000187:drug effects / Q000502:physiology
D002245:Carbon Dioxide; D010121:Oxytocin; D000324:Adrenocorticotropic Hormone; D010100:Oxygen; D006854:Hydrocortisone