Prostaglandins in the sheep fetus: implications for fetal function.

Area of Science:

• Reproductive biology
• Fetal physiology
• Endocrinology

Background:

• Prostaglandins (PGs) play critical roles in pregnancy and parturition.
• Understanding fetal prostaglandin dynamics is crucial for monitoring fetal well-being and development.

Purpose of the Study:

• To investigate the concentrations and changes of prostaglandin E (PGE) and prostaglandin F (PGF) in fetal plasma and other fluids during late pregnancy and around parturition.
• To examine the effects of exogenous PGE2 administration on fetal physiological parameters and hormone levels.

Main Methods:

• Chronically catheterized sheep fetuses were used to measure PGE and PGF concentrations in plasma, tracheal fluid, amniotic fluid, and urine.
• Fetal blood gas, pH, hematocrit, blood pressure, and heart rate were monitored.
• Hormone levels (growth hormone, prolactin, cortisol) were analyzed before and after PGE2 infusion.

Main Results:

• Fetal plasma PGE concentrations were higher than PGF and increased before delivery, decreasing rapidly after birth.
• Maternal uteroovarian vein showed increased PGF but not PGE before parturition.
• Fetal PGE and PGF levels in tracheal fluid showed minor changes, while amniotic fluid levels increased in late pregnancy.
• Surgery elevated PGE and PGF in fetal plasma and tracheal fluid temporarily.
• Hypoxemic fetuses had elevated plasma PGE; acute hypoxia/hypercapnia did not consistently alter prostaglandin levels.
• Exogenous PGE2 infusion raised fetal plasma cortisol but did not affect other measured physiological parameters or hormones (growth hormone, prolactin).

Conclusions:

• Fetal prostaglandin profiles change significantly around term, distinct from maternal patterns.
• PGE2 administration can stimulate fetal cortisol release, even when the adrenal gland's response to ACTH is limited.