Spontaneous and ionophore-induced ability of spermatozoa to acrosome-react was examined in asthenozoospermic infertile patients and fertile donors. Spermatozoa were washed free of seminal plasma and capacitated in B2 medium for 2 h at 37 degrees C. Subsequently 5, 10, 20 and 30 microM A23187 (final concentrations) were added to equal aliquots of these samples and incubated for an additional 30 min. The acrosome reaction was then determined by the triple stain technique. The percentage of spontaneous reaction (no ionophore) in asthenozoospermic samples was similar to that in fertile samples (4.2 and 3.8, respectively). However, the ionophore-induced reaction rate remained significantly lower in asthenozoospermic samples than in normozoospermic samples.
Hyperactivated motility of capacitated sperm was studied before and after contact for 30 min with the Ca2+ ionophore A23187. Sperm from fertile donors and asthenozoospermic infertile patients were incubated in the presence of increasing concentrations of A23187 in the medium. At 5-10 microM, the ionophore induced a significant increase (P less than 0.05) in the percentage of hyperactivation of sperm from asthenozoospermic subjects. Higher concentrations (20 and 30 microM) were needed to enhance hyperactivation of sperm in the fertile population. In the latter, extended contact with the ionophore induced no significant change compared to a 30-min incubation period. Since this type of movement is an essential feature of the fertilizing gamete, a low hyperactivation rate may partly explain fertilization failure in the asthenozoospermic group.
High-ionic-strength media are known to favor rapid capacitation and acrosome reaction of spermatozoa in vitro. The influence of isoosmolar (N-BWW) and hyperosmolar (H-BWW) media on the percent motility, forward progression, and zona-free hamster egg penetration has been investigated for 148 semen from patients consulting for male or idiopathic sterility. After 15 h of incubation, the hyperosmotic medium had no significant detrimental effect on the percent motility of spermatozoa, although the forward progression was better maintained in the isoosmolar medium. In general egg penetration was increased when spermatozoa were treated with the hypertonic medium, and in particular 5 patients whose semen showed no penetration when treated with N-BWW scored > 12% when treated with H-BWW. For the 23 subjects who had an IVF at the same period, a good agreement with zona-free egg penetration was found in 70% of the cases.
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.
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