Transport of spermatozoa in the reproductive tracts of mares.

The research study outlines the development of a scintigraphic method to monitor sperm movement in mares’ reproductive tracts, utilizing a radiolabelling solution prepared from Technetium-99m and hexamethyl propylene amine oxime.

Research Methodology

• The researchers developed a scintigraphic method specifically for studying sperm migration in the reproductive tracts of mares.
• The study involved five mares and two stallions for preliminary tests, and an additional three mares and one stallion for the main experiment.
• An isotopic radiolabelling solution was created using Technetium-99m and hexamethyl propylene amine oxime, which was then used to label the spermatozoa.
• To ensure optimized labelling, spermatozoa were incubated with the radiolabelling solution for 20 minutes at 20 degrees Celsius, which resulted in a labelling rate of 57-72%.

Procedure and Findings

• Any radioactivity outside the spermatozoa was eliminated by centrifugation and washing with skimmed milk extender.
• The radiolabelled sperm was then introduced into the uterine bodies of detomidine-sedated mares in oestrus and scintigraphic images were obtained over a period of 4.5 hours post-insemination.
• The movements of the sperm were tracked using both dynamic and static scans.
• Results indicated that the radiolabelled sperms reached the uterine horns approximately 8-20 minutes after insemination. The number of uterine contractions in the 30 minutes following insemination ranged from 5 to 65 across the different mares.
• After one hour post-insemination, the majority of the sperm activity was found in the uterus. At the 2.5-hour mark, most sperm had exited the uterus and were either in the vagina or discharged.
• By the 4.5-hour mark, few traces of sperm activity were detected in the uterus, with minimal activity in the vagina as most spermatozoa had been eliminated from the mares.

Implications of the Study

• This study delivers a novel method to explore and monitor sperm movement in the equine reproductive tract, enhancing understanding of equine fertility and potentially informing the development of fertility treatments for horses.
• The findings also provide new insights, quantitatively and qualitatively, into the kinetics of sperm migration within the mare’s reproductive tract.