Studies on a local effect of boar seminal plasma on ovulation time in gilts

Previous studies showed that intrauterine infusion of seminal plasma at the onset of oestrus could advance ovulation in pigs, possibly to enhance the chances of fertilization by optimizing the chronological events of fertiliz ation. This effect has been attributed to a local unilateral mechanism wher eby infusion into a single uterine horn advances ovulation in the adjacent ovary. The present study was designed to elucidate possible mechanisms of l ocal signal transduction. In a series of five experiments using 43 gilts, t he ovarian response was investigated after infusion of seminar plasma at di fferent sites of the female reproductive tract. The time of ovulation was d etected sonographically at 4- or 2-h intervals. Single uterine horn infusio n of 100 ml seminal plasma advanced ovulation on the ipsilateral ovary by 9 .3 h (mean) compared with the contralateral ovary. Dissection of the ipsila teral isthmus abolished the unilateral seminal plasma effect. Unilateral in fusion of 50 mu l or 1 ml seminal plasma or 50 mu l of the concentrated 1-1 0 kDa fraction in the lower isthmus was ineffective. Application of 5 ml se minal plasma into the tip of a ligated uterine horn lead to 3.6 h (mean) ea rlier ovulation on the adjacent ovary. In contrast, the infusion of 5 ml Na Cl showed no effect. Application of 5 ml seminal plasma in the middle of th e uterine horn between two ligatures was ineffective. It is concluded that, for the transduction of the local signal involved in the advancement of ov ulation, contact of seminal plasma with the epithelium of the utero-tubal j unction is essential.