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Does the ovine placenta secrete ACTH under normoxic or hypoxic conditions?
1Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville 32605.
The American Journal of Physiology
|February 1, 1991
Summary
This study investigated adrenocorticotropic hormone (ACTH) in the ovine placenta. Results indicate the ovine placenta does not secrete ACTH into maternal or fetal circulation, even during hypoxia.
Area of Science:
- Reproductive Endocrinology
- Fetal Physiology
Background:
- Maternal and fetal plasma cortisol and adrenocorticotropic hormone (ACTH) increase in late ovine pregnancy.
- The placenta's role in ACTH regulation is not fully understood in many species.
Purpose of the Study:
- To determine if the ovine placenta contains ACTH.
- To assess net ACTH secretion by the uteroplacental unit into maternal or fetal circulation.
Main Methods:
- Pregnant ewes and fetuses were surgically prepared with arterial and venous catheters.
- Arteriovenous differences in ACTH, PO2, PCO2, and progesterone were analyzed across the placenta before and during induced hypoxia.
- Catheter placement was validated by analyzing gas and hormone gradients.
Main Results:
- Hypoxia significantly decreased fetal and maternal arterial PO2.
- Hypoxia caused a substantial increase in fetal and maternal arterial ACTH immunoreactivity.
- No net secretion of ACTH was detected across the ovine placenta into either maternal or fetal circulation.
Conclusions:
- The ovine placenta does not appear to contain or secrete ACTH.
- The observed increases in fetal and maternal ACTH during hypoxia are likely of pituitary origin, not placental.
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