The effect of albumin gradients and human serum on the longevity and fertilizing capacity of human spermatozoa in the hamster ova penetration assay.

The motility and the capability to penetrate zona-free hamster eggs of Y-enriched or washed sperm were evaluated after protracted in vitro incubation with and without the addition of preheated human serum. The addition of 50% preheated serum decreased the motility loss over time for both the washed and Y-enriched sperm. Such motility loss was decreased by 25% and 27% at 20 hours, by 31% and 39% at 30 hours, and by 30% and 40% at 40 hours of incubation for the washed and Y-enriched sperm, respectively. The washed and Y-enriched sperm suspensions with and without addition of preheated human serum achieved 100% penetration rate after 2 hours of preincubation. However, when scored by the sperm per egg ratio, washed sperm achieved 1.2 +/- 0.2 (mean +/- standard error [SE]) sperm per egg, while the Y-enriched sperm achieved 3.0 +/- 0.4 sperm per egg. After 24 hours of incubation, penetration by washed sperm decreased to a mean of 62.8%. The Y-enriched sperm penetrated a mean of 18% of the ova. Addition of preheated serum increased the egg penetrating capacity of washed sperm at 24 hours but failed to improve the Y-enriched spermatozoa. This study suggests that for optimum conception rates, precise ovulation timing is crucial when Y-enriched fractions are used for insemination.