Effect of progesterone on prostaglandin F2 alpha secretion and outcome of pregnancy during cloprostenol-induced abortion in mares.

This study explores the effect of progesterone on achieving successful pregnancy in mares, drawing upon cloprostenol-induced abortions. The research indicates that progesterone may inhibit the secretion of prostaglandin F2 alpha which is associated with early abortions, showing potential for progestogens to be used to prevent terminations in horses when their pregnancies are at risk due to disorders causing elevated prostaglandin secretion.

Research Methodology

• The study involved 16 pregnant mares. Their pregnancies were terminated using an agent, cloprostenol, which was given daily until expulsion of the fetus or for a span of 5 days.
• In experiment 1, mares between 98 to 153 days pregnant were given progesterone daily for 5 days, starting 18 hours after the first administration of cloprostenol.
• In experiment 2, mares between 93 to 115 days pregnant were given altrenogest (another type of progestin), every day starting 12 hours after the first administration of cloprostenol.
• A control group of mares between 82 to 102 days pregnant were given cloprostenol daily until they expelled the fetus.

Study Findings

• In the control group, abortion occurred after 2 to 3 cloprostenol administrations, and significant increases in PGF2 alpha secretion were associated with the expulsion of the fetus.
• In contrast, pregnancy did not terminate in 5 of 8 of the progesterone-treated mares and in all 8 of the altrenogest-treated mares. These successfully maintained pregnancies were linked with inhibition of endogenous PGF2 alpha secretion as compared with values in mares that went through an abortion.

Conclusions

• The researchers concluded that circulating progestogen concentrations could influence the outcome of an abortion when using the agent prostaglandin for termination.
• The change in prostaglandin secretion could be due to a direct effect of the hormone progesterone, or it could come from the process of the abortion itself.
• These results suggest that progestogens may be beneficial in preventing abortions in mares when they are at risk of pregnancy termination due to diseases that cause an excess of prostaglandin secretion.