Hamster egg penetration: comparison of preincubation periods

Seven-hour and 20-hour incubation periods were tested with donor specimens to be used in the hamster egg sperm penetration assay (SPA). Aliquots of the washed sperm were incubated in air and in 5% CO2 and 95% air at 37 degrees C for comparison of sperm survival rates. The mean penetration for the donors ranged from 0% to 64%, with group means of 21% and 36% for the 7- and 20-hour incubations, respectively. All donors had penetration rates in the fertile range after 20 hours of incubation, but 33% (3 of 9) had penetration rates less than 10% after 7 hours of incubation. Incubation of sperm in air reduced the motility by 9% after 20 hours. The results suggest that the 20-hour incubation in 5% CO2 is better because it reduces the possibility of false-negative results in the SPA. We conclude that penetration in the questionable range of 10% may require further SPA testing with different incubation periods and technique modifications, such as a sperm rise step to increase sperm motility and reduce the number of leukocytes.