The ability of feline spermatozoa in different epididymal regions to undergo capacitation and acrosome reaction

The sperm maturation process that occurs in the epididymis is a necessary process for spermatozoa to acquire motility and the ability to undergo capacitation, which is an important key for fertilization. The aim of this study was to evaluate the ability of feline spermatozoa from different regions of the epididymis to undergo capacitation and acrosome reaction. Experiment I: epididymal spermatozoa from caput, corpus and cauda regions were placed in phosphate buffered saline (control medium) and in vitro fertilization medium (capacitating conditions). Sperm motility, motility patterns, plasma membrane integrity and tyrosine phosphorylation were evaluated at time 0 and 60 min after incubation. Experiment II: spermatozoa were treated with 2 μM of calcium ionophore (A23187) to induce the acrosome reaction and acrosome reaction was evaluated. The results showed a significant effect of region with a higher percentage of tyrosine phosphorylation in spermatozoa from the cauda than in the caput or corpus regions (P = 0.0061; P = 0.0088). Spermatozoa from corpus and cauda showed higher values in the majority of the measured motility parameters than spermatozoa from the caput (P < 0.0001). Spermatozoa from all epididymal regions can undergo the acrosome reaction in vitro in response to induction by calcium ionophore with no difference between regions (P > 0.05). Spermatozoa from all epididymal regions were able to undergo capacitation. Higher percentage of tyrosine phosphorylation in spermatozoa from the cauda reflect that they more easily underwent capacitation compared to spermatozoa from caput and corpus which required more time of incubation for capacitation. In conclusion feline epididymal spermatozoa from all regions can undergo capacitation and acrosome reaction in vitro and do not require incubation under capacitating conditions.