Further studies on the use of synthetic prostaglandin analogues for inducing luteolysis in mares.

This research investigates the use of synthetic prostaglandin analogues, specifically ICI-81008 and ICI-79939, in mares for inducing luteolysis, the regression of the corpus luteum, to manage infertility issues. The study found that ICI-81008 effectively stimulated luteolysis with less toxicity compared to ICI-79939, suggesting its potential value in equine reproductive management.

Background and Objective

• Prostaglandin F2a (PGF2a) is known to end the lifespan of the cyclical corpus luteum, an essential structure for pregnancy in many species. The synthetic analogues of PGF2a can also induce luteolysis, thereby allowing for the onset of oestrus (a recurring period of sexual receptivity and fertility).
• The aim of this research was to further explore the luteolytic ability, toxicity, and clinical value of two synthetic prostaglandin analogues, ICI-81008 and ICI-79939, on mares. This could potentially help address infertility problems in mares by triggering oestrus.

Methodology and Findings

• The study elaborated on the luteolytic action of both ICI-79939 and ICI-81008 in mares. The compounds’ effects on inducing luteolysis and oestrus were observed in different species within mares such as Welsh Pony mares and Thoroughbred mares, using various dosages.
• Results showed that ICI-81008 induced luteolysis in Welsh Pony mares at a dose of 125 μg and in Thoroughbred mares at 250 μg. Side effects from ICI-81008 only became observable at doses six to eight times higher than the minimum effective dose.
• For ICI-79939, however, adverse side effects appeared at only three to four times the normal luteolytic dose. Although it appeared to be more efficient at inducing luteolysis, its toxicity at higher dosages presented concerns.

Implications and Conclusion

• Main findings show that ICI-81008, although slightly less potent, is considerably less toxic and thus considered safer. This is crucial because side effects are a significant concern when administering such compounds to livestock.
• Regarding infertility issues in mares, administering a less toxic but effective dose of ICI-81008 proves to be reliable in inducing luteolysis and a return to oestrus, especially in non-cycling mares suffering from prolonged dioestrus.
• Overall, the research reinforces the potential use of synthetic prostaglandin analogues, particularly ICI-81008, in enhancing equine reproductive management. The findings also offer validation for further clinical application of this compound to improve the conception rates in mares.