Prostaglandins in maternal and fetal plasma and in allantoic fluid during the second half of gestation in the mare.

This study measures levels of certain prostaglandins (PGs), which are fat-soluble compounds that carry out various biological functions, in maternal and fetal plasma and in allantoic fluid in mares during the second half of pregnancy. The researchers found that the levels of these PGs rose gradually with advancing pregnancy and that substantial changes in these levels were associated with early birth, highlighting their potential significance in gestational regulation and parturition.

Methodology and Results

• The researchers conducted this study using mares and their fetuses that had been chronically catheterized – a process wherein a tube is inserted to allow constant access for taking samples.
• The primary PGs studied were: PGF-2 alpha and PGE-2, and their metabolite 13,14-dihydro-15-oxo-prostaglandin (PGFM).
• As the gestational age increased, a gradual rise was observed in all three PGs across all study mediums – maternal and fetal plasma and allantoic fluid.
• Among these, the highest levels of PGE-2 and PGF-2 alpha were found in the allantoic fluid and the least in maternal plasma. The PGFM concentrations, however, were highest in maternal plasma.
• Significant variances in PGFM concentration between the venous and arterial plasma were noted across the uterine circulation used in the span of 100 days (180-280 days).

Prostaglandin Changes and its Effects

• A rise of around three-to-five-fold in maternal PGFM levels linked with fasting or intrauterine surgery was almost completely eliminated by meclofenamic acid, which is an inhibitor of prostaglandin synthetase. This means that the acid could potentially regulate PG levels in situations of stress or invasive procedures.
• The researchers noted that the premature delivery of the foal was preceded by increases in PGE-2 and PGF-2 alpha in the fetal fluids. This suggests that these two PGs could play a role in initiating early labor.
• However, changes in these PG concentrations in the maternal plasma were minimal even 10-20 hours before delivery, indicating that maternal plasma levels of these PGs may not be a reliable predictor of imminent delivery.