Induction of luteolysis in mares by ultrasound-guided intraluteal treatment with PGF2alpha.

The research explores the method of using ultrasound-guided luteal injection in horse mares to induce luteolysis, a process that dismantles the corpus luteum (a temporary endocrine structure involved in pregnancy) in the ovary. The study found that local administration of a hormone, PGF2alpha, was effective at much lower doses compared to systemic administration, opening up possibilities for studying the effect of different substances on luteal function.

Study Design and Method

• The study involved horse mares divided into different groups (7 to 9 per group) and treated on the 9th day after ovulation.
• The treatment consisted of a hormone known as PGF2alpha, given either a systemic route (through muscle) or a local intraluteal route (directly into the corpus luteum).
• The doses used varied from zero (control), 0.01 mg, 0.1 mg to 5 mg per dose, with the local intraluteal treatment being given at extremely lower doses (up to 50-fold lower) to evaluate the efficacy of this method.

Assessment of Luteolytic Efficacy

• The effectiveness of each treatment was ascertained based on a decrease in progesterone concentration (the hormone secreted by the corpus luteum), the interval to uterine edema (an indicator of the onset of luteolysis), and the interovulatory interval (time between two ovulatory cycles).
• It was observed that the local administration of PGF2alpha directly into the corpus luteum consistently caused luteolysis, even at much lower doses than the systemic route.
• Progesterone concentrations substantially reduced to less than 10% within two days post-treatment in mares treated with either 5 mg PGF2alpha intramuscularly or 0.1 mg PGF2alpha intraluteally.

Findings and Conclusion

• The study concluded that the minimum effective luteolytic dose of PGF2alpha administered intraluteally stood between 0.01 and 0.1 mg.
• The ultrasound-guided intraluteal injection technique showed promise as a feasible method for studying the direct impact of other chemicals on luteal function.
• However, the research also noted that this approach carries a degree of risk, as three intraluteal injections were associated with the development of ovarian abscesses or infections in the ovary.