In vitro fertilization of bovine oocytes in the presence of theophylline

Abstract

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).