Luteolytic factor in stallion semen.

The research seeks to investigate whether stallion semen contains a luteolytic factor, a substance that promotes the breakdown of the corpus luteum in the ovaries, by comparing its effects with a known luteolytic agent, Prostaglandin F2alpha (PGF2a), on pseudopregnant rabbits.

Objective of the Study

• The study was designed to explore the hypothesis that stallion semen might contain a luteolytic factor, which could bring about the process of luteolysis – the degradation of the corpus luteum after ovulation.
• This hypothesis was based on previous work which indicated ovulation could be triggered in mares by introducing stallion semen into their uterus.
• The researchers compared the action of known luteolytic substance, Prostaglandin F2alpha, and stallion semen on the corpus luteum which is an endocrine structure in females that forms at the site of an ovarian follicle after ovulation.

Methodology

• 33 pseudopregnant rabbits were divided into three groups, with each group receiving different treatment.
• Ovulation was induced in all rabbits using a hormone HCG (Human Chorionic Gonadotropin).
• Group A (control group) was treated with physiological saline on two specific days after ovulation. Group B (which consisted of two subgroups) was treated with PGF2a on different schedules. Group C received 2 ml of stallion semen, again on different schedules.

Outcomes and Analysis

• 48 hours after the second treatment, the ovaries of these rabbits were removed for analysis.
• Macroscopically, no differences were seen between the ovaries from different experimental groups.
• The corpus luteum (CL) from each ovary, irrespective of the treatment received, appeared pink and vascularized, showing no signs of luteolysis. The average weight was 23±16 milligrams.
• However, histological examination revealed distinct differences in the appearance of the luteal cells (cells of the corpus luteum) between different treatments. These differences were observed independent of whether the CL was present in the ovary that was ipsilateral or contralateral to the treated uterine horn.