Objective: To assess the fertilizing capacity of human sperm preserved in electrolyte-free (EF) solution at 4 degrees Celsius.
Methods: The motility, acrosome status and fertility index of human sperm were respectively assessed before and after preservation in cold EF solution.
Results: The motility of human sperm so preserved for one week was significantly higher than that of the sperm preserved in modified human tubal fluid (43.4+/-7.9% vs 9.5+/-2.5%, P<0.01). Although acrosome status of human sperm in EF solution before reinitiation differed little from that of fresh sperm (capacitated sperm: 7.6+/-1.8% vs 6.4+/-1.8%; acrosome-reacted sperm: 3.0+/-1.7% vs 2.4+/-1.1%, P>0.05), the percentage of capacitated and acrosome-reacted sperm in the EF solution significantly increased after reinitiation (16.0+/-2.3% vs 7.6+/-1.8% and 9.4+/-2.1% vs 3.0+/-1.7% respectively, P<0.01). The penetration rate and fertility index of the sperm in EF solution were comparable with those of fresh sperm (48.1% vs 50.9%; 1.38+/-0.16 vs 1.29+/-0.13, respectively).
Conclusions: Preservation in cold EF solution does not induce human sperm to undergo capacitation and acrosome reaction, and the sperm so preserved for one week possesses comparable fertilizing capacity as fresh sperm does.