[Evaluation of the fertility of human sperm by interspecies (man-hamster) in vitro fertilization].

An "in vitro" fertilization test employing zona-free hamster eggs was used to analyse human spermatozoal fertilizing ability. Sperms from 28 men (group 1) whose wives were candidates for "in vitro" fertilization and embryo transfer, and from 5 men belonging to infertile couples (group 2), were evaluated for their ability to penetrate and decondense in zona-free hamster ova. All men had spermiograms in the normal range. A total of 529 eggs were inseminated with spermatozoa from group 1 and the fertilization rate was found to range from 8% to 100% with an average of 57.5%. Of the 130 ova tested with sperm from group 2 individuals, only one showed any evidence of penetration. The fertilization rate and the degree of polyspermy failed to show a significant correlation with sperm concentration in the ejaculate or motility. This cross-species system is a useful additional test to the classic spermiogram and may have a potential value as a diagnostic tool in evaluating human spermatozoal fertilizing capacity, avoiding the ethical and logistical problems associated with fertilization of human eggs "in vitro".