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 di fferent bulls. Dose response was varied among individual bulls, but th eophylline at 2.5-5 mM enhanced sperm fertilization of cumulus-intact oocytes by accelerating the time of fertilization in vitro. For cumulu s-free oocytes, no beneficial effect of theophylline on sperm fertiliz ing ability was observed even when sperm were pre-incubated with theop hylline for 4-5 h before insemination. It is suggested that sperm migh t be capacitated by cumulus cells surrounding the oocyte, and that the ophylline could increase the probability of sperm contact with the cum ulus-oocyte complexes and might facilitate cumulus-induced capacitatio n and/or zona-induced acrosome reaction. In the presence of theophylli ne, sperm penetration into cumulus-intact oocytes required 4 h. The ra te of fertilization varied among individual bulls, and reached a maxim um level at 12-20 h after insemination. Subsequent developmental capac ity of fertilized oocytes was also determined after fertilization by c o-culture with bovine oviduct epithelial cells. Seven days after in vi tro fertilization 18.1-22.7% of the inseminated oocytes had developed into blastocysts (150-160 cells).