Restoration of Motility in Acrosome-Reacted Boar Spermatozoa Induced by the Ionophore 4-Br-A23187.

The acrosome reaction (AR) is a calcium-dependent exocytotic event required for successful fertilization. Calcium ionophores are commonly used to induce AR in vitro; however, this treatment is associated with a significant loss of sperm motility. The aim of this study was to evaluate the recovery of motility in boar spermatozoa after ionophore-induced AR and to assess the role of extracellular calcium. Boar spermatozoa were incubated with 10 μM 4-Br-A23187 to induce AR. Then, spermatozoa were washed and incubated for 30 min in a recovery medium containing either 1 mM calcium or 5 mM EGTA. The AR was analysed by flow cytometry, and motility parameters were assessed using a CASA system. Ionophore treatment induced AR and caused a marked reduction in sperm motility, which was partially recovered in the presence of 5 mM EGTA, but not in the presence of 1 mM calcium. These results suggest that extracellular calcium inhibits the restoration of motility after ionophore-induced AR in boar spermatozoa.