Characterization of the Sperm Penetration Bioassay

Abstract

Parameters influencing the zona‐free hamster egg bioassay for human sperm fertility potential were evaluated. Egg recovery from hamsters superovulated at random with respect to their estrous cycle was enhanced when the PMS‐HCG time interval was lengthened. Prolonged egg exposure to trypsin during zona removal did not adversely affect egg viability. A swim‐up procedure for washing human sperm was superior to a centrifugation‐resuspension technique, although the yield of washed cells was low. The kinetics of sperm capacitation were examined for six different donors over a 22‐hour time period. Capacitation in 0.3% albumin was maximal after 6.5 hours, and penetration scores in five of the six donors declined thereafter. In 3.5% albumin, capacitation was slower with peak penetration levels observed at 13.5 hours. Much higher penetration was noted when sperm, capacitated in 3.5% albumin, were compared with those exposed to 0.3%. Specific recommendations for optimizing bioassay outcome are summarized.