PENTOXIFYLLINE ACTS SYNERGISTICALLY WITH A23187 TO INCREASE THE PENETRATION OF ZONA-FREE HAMSTER OOCYTES BY CRYOPRESERVED HUMAN SPERMATOZOA

The number of cryopreserved human spermatozoa which penetrated zona-fr ee hamster oocytes after stimulation with 2 mu mol A23187 per litre wa s increased by the further addition of 0.6 or 3.6 mmol pentoxifylline per litre. With spermatozoa prepared by washing by repeated centrifuga tion, the median numbers of sperm heads/egg were 1.9, 7.9 and 10.8 in the presence of 0, 0.6 or 3.6 mmol pentoxifylline per litre, respectiv ely. A similar effect was observed with spermatozoa prepared on a Perc oll gradient. As A23187 inhibited sperm motility, and this was exacerb ated by pentoxifylline, the increased penetration rate of hamster oocy tes cannot be explained by improved sperm motility. The number of sper matozoa stimulated to acrosome react by 2 mu mol A23187 per litre was increased 3-fold by 3.6 mmol pentoxifylline per litre and 4-fold by 5 mmol caffeine per litre. These data suggest that cAMP may act synergis tically with Ca2+ to stimulate the acrosome reaction. Pentoxifylline m ay improve the fertility of poor-quality human spermatozoa by enhancin g their ability to respond to the Ca2+ signal produced by binding to t he zona pellucida.