Effect of steroids and oviductal cells, from the different parts of the oviduct, on the incidence of monospermy in porcine in vitro fertilization

A high incidence of polyspermy occurs in porcine in vitro fertilization. It is also known that in vivo, the oviductal cells and their secretions play an important role in fertilization and early development. Vesicles from oviductal cells from different parts of the oviduct (isthmus or ampulla) pretreated with estradiol or progesterone or ethanol were used to assess their role in the fertilization process. Oviductal cells were co-cultured with 0.5 million motile sperm/ml for 30 min. A 10-microl sample (spermatozoa bound with the cells) was added to 40-microl droplets of fertilization medium containing 5 oocytes. After 15 to 18 h, oocytes were examined for penetration and monospermy. The results show a lower penetration rate with oviductal cells than that of the control. The use of oviductal cells from the isthmus treated with estradiol significantly decreased the percentage of polyspermy compared with that of ampulla treated with the estradiol or with the control. When the isthmus cells were treated with progesterone, an increase in the incidence of polyspermy was observed. Therefore, it is possible to use oviductal cells to increase the incidence of monospermy in porcine in vitro fertilization; moreover, estradiol increases the proportion of monospermy when added to isthmus-derived oviductal cells.