Penetration of zona-free hamster, bovine and equine oocytes by stallion and bull spermatozoa pretreated with equine follicular fluid, dilauroylphosphatidylcholine or calcium ionophore A23187.

This research article examines the efficiency of follicular fluid, dilauroylphosphatidylcholine, and calcium ionophore A23187 in inducing capacitation in stallion and bull spermatozoa, which is critical for successful oocyte penetration. The results suggest that both dilauroylphosphatidylcholine and calcium ionophore A23187 can induce successful capacitation, whether the oocytes are homologous or heterologous.

Objective and Methodology of the Study

• The research primarily aimed to assess the capacitation of stallion and bull spermatozoa by testing their capability to penetrate zona-free oocytes after treatment with follicular fluid (FF), dilauroylphosphatidylcholine (PC12), and calcium ionophore A23187 (A23187).
• The spermatozoa suspensions were prepared and incubated at 37 degrees Celsius with one of the six treatments. These include a modified Tyrode’s medium alone, or in combination with FF, PC12, or A23187.
• After incubation, these treated sperm were brought into contact with oocytes from a hamster, bovine, and equine, and allowed to interact for three hours. Post-interaction, the oocytes were stained and examined for successful sperm penetration.

Results and Observations

• It was observed that fewer hamster oocytes were penetrated by sperm treated with only BGM3 medium or follicular fluid as compared to those treated with PC12 or A23187.
• There was no significant difference in oocyte penetration by stallion sperm collected through a swim-up procedure or centrifugation through a Percoll gradient.
• PC12 or A23187 treatment empowered both stallion and bull spermatozoa to penetrate oocytes, but more bovine oocytes were penetrated by bull sperm than by stallion sperm.
• However, the penetration of zona-free hamster and equine oocytes by bull sperm and stallion sperm was comparable, irrespective of the treatment.

Conclusions

• The study confirmed that both PC12 and A23187 could capacitate stallion and bull spermatozoa, triggering the acrosome reaction, a necessary condition for sperm to penetrate oocytes effectively.
• While the research clearly demonstrates that sperm treatment can influence success in oocyte penetration, the efficacy is also dependent on the species of both the sperm and the oocytes.