Partial characterization of an equine conceptus prostaglandin inhibitory factor.

This research studied the chemical properties and potential roles of a substance produced by horse embryos that suppresses a specific prostaglandin, potentially playing a crucial role in preventing a horse’s pregnancy from being interrupted.

Understanding the Research

• The study was primarily focused on a unique substance, known as prostaglandin inhibitory factor (PIF), which is produced by horse embryos in the early days of pregnancy.
• The researchers collected embryos from pregnant mares 13 days after ovulation, and studied them under in vitro conditions. The embryos were placed in a culture for 24 hours, and the medium in which the embryos grew was extracted and termed the ‘equine conceptus conditioned media’ (CCM).

Figuring out the Prostaglandin Inhibitory Factor (PIF)

• The CCM was then assayed, or analysed, for its potential antiluteolytic capabilities. An antiluteolytic is a chemical that holds back luteolysis which usually occurs at the end of the ovulation cycle to prepare for a potential new cycle.
• It was found that the CCM showed significant antiluteolytic activity at specific time intervals – 12 hours, 18 hours, and 24 hours after the embryos were placed in culture.
• Further study revealed that this antiluteolytic activity was present in a fraction that had molecules of a size ranging from 3-10 kiloDalton (kDa).

Testing the Resiliency of PIF

• The researchers found that proteinase K, an enzyme known for breaking down proteins, could not destroy this antiluteolytic activity. This suggests that PIF is resistant to commonly occurring protein-degrading enzymes.
• Contrarily, the team observed that dextran-coated charcoal could remove this antiluteolytic activity from the CCM, suggesting that the PIF is adsorbable by the charcoal.

Role of PIF in Pregnancy

• From these observations, it is inferred that the PIF produced by horse embryos is a small (3-10 kDa), protein-digesting enzyme-resistant substance that can be adsorbed by dextran-coated charcoal.
• Given its antiluteolytic properties and its production timeline, the researchers suggest that the PIF plays a significant part in signaling the continuation of pregnancy in mares. This is because it inhibits the body’s preparation for a new ovulatory cycle, thereby allowing the existing pregnancy to progress.