Although mammalian sperms are cryopreserved for in vitro fertilization a process of cryopreservation decreases the fertility. Acrosome reaction requires depolarization-induced ca^(2+) influx and ca^(2+) releases from the ca^(2+) stores. To examine whe...
Although mammalian sperms are cryopreserved for in vitro fertilization a process of cryopreservation decreases the fertility. Acrosome reaction requires depolarization-induced ca^(2+) influx and ca^(2+) releases from the ca^(2+) stores. To examine whether the cellular ca^(2+) mobilization is altered by a sperm cryopreservation we compared cytosolic ca^(2+) signals between fresh and cryopreserved pig sperms using confocal ca^(2+) imaging. The magnitudes of depolarization-induced ca^(2+) increases were significantly smaller in cryopreserved sperms. Exposures to 10 mM caffeine or 5 μM thapsigargin elicited less ca^(2+) increases in the cryopreserved sperms compared to fresh sperms. In addition, progesterone-triggered ca^(2+) rises, that are thought to enhance acrosome reaction, were completely abolished in the cryopreserved sperms. These results suggest that storage and(/or) release of ca^(2+) from the intracellular ca^(2+) stores in pig sperms are significantly impaired by the process of cryopreservation.