IN-VITRO FERTILIZATION OF BOVINE OOCYTES IN THE PRESENCE OF THEOPHYLLINE

To determine the effect of theophylline on in vitro fertilization, in vitro matured bovine oocytes were co-incubated with sperm from four different bulls. Dose response was varied among individual bulls, but theophylline at 2.5-5 mM enhanced sperm fertilization of cumulus-intact oocytes by accelerating the time of fertilization in vitro. For cumulus-free oocytes, no beneficial effect of theophylline on sperm fertilizing ability was observed even when sperm were pre-incubated with theophylline for 4-5 h before insemination. It is suggested that sperm might be capacitated by cumulus cells surrounding the oocyte, and that theophylline could increase the probability of sperm contact with the cumulus-oocyte complexes and might facilitate cumulus-induced capacitation and/or zona-induced acrosome reaction. In the presence of theophylline, sperm penetration into cumulus-intact oocytes required 4 h. The rate of fertilization varied among individual bulls, and reached a maximum level at 12-20 h after insemination. Subsequent developmental capacity of fertilized oocytes was also determined after fertilization by co-culture with bovine oviduct epithelial cells. Seven days after in vitro fertilization 18.1-22.7% of the inseminated oocytes had developed into blastocysts (150-160 cells).