Acrosome-reacting capacity of frozen-thawed human semen: relation to hamster ova penetration

Interspecies egg penetration requires completion of capacitation and acrosome reaction of the spermatozoa. The ability of frozen-thawed human semen to accomplish this reaction was studied, and its relation to the zona-free hamster egg penetration was investigated. The percentage of reacted cells in the population of live spermatozoa estimated by the triple-staining technique was found to be greater in frozen than in fresh samples. However, the egg-penetrating ability of cryopreserved semen remained significantly low. Individual differences in the ability to undergo the acrosome reaction and its relation to penetration are discussed.