Preincubation of human spermatozoa in test-yolk medium: effect on penetration of zona-free hamster oocytes and correlation with other semen characteristics.

Penetration of zona-free hamster oocytes by human spermatozoa after preincubation with BWW medium (standard technique) or a buffer system containing egg yolk (TESTY) was compared by applying both treatments to aliquots of 60 ejaculates from 34 patients. The TESTY-treated spermatozoa penetrated the oocytes much more successfully than the spermatozoa treated by the standard technique. Although the penetration levels achieved by the two methods were significantly correlated, the correlation coefficient was too low to predict the penetration outcome from one technique to the other. More consistent results were obtained when different ejaculates from the same donor were treated by TESTY than by the standard technique. Spermatozoan penetrating ability was more strongly correlated with sperm concentration, motility, and morphology after treatment by the standard technique than after TESTY treatment. Much larger differences in penetration were present between normal and abnormal ejaculates when the standard technique was used than TESTY.