Postovulatory effect of repeated administration of prostaglandin F2alpha on the endocrine status, ova transport, binding of accessory spermatozoa to the zona pellucida and embryo development of recently ovulated sows.

We investigated the postovulatory effect of repeated administration of prostaglandin F2alpha (PGF2alpha) on the endocrine status, ova transport, binding of accessory spermatozoa to the zona pellucida (ZP) and embryo development of recently ovulated sows. We used altogether 10 Swedish crossbred (Landrace x Yorkshire) multiparous sows. The treatment group (P-group) was administered 1 mg of PGF2alpha intravenously every 6 h via an indwelling jugular cannula, commencing 4-8 h after ovulation was detected in the second estrus after weaning. All sows were inseminated once and blood was sampled until the end of the experimental period. After slaughter, we immediately recovered the reproductive tracts and divided them into three equal isthmic segments (IST1, IST2 and IST3) and a third of the uterine horn from the utero-tubal-junction (UTJ), and we flushed each one with PBS for ova recovery. We immediately stained the ova and examined them under epi-fluorescence illumination. We found the highest proportion of ova in the P-group in IST1 (41.5%), while we found the highest proportion in the C-group in the uterus (40.7%). A total of 68.7% of ova in the P-group had more than 50 accessory spermatozoa attached to the ZP, compared with 36.7% in the C-group sows. A total of 77% of ova had more than three blastomeres in the P-group, compared with 73% in the C-group. PGF2alpha metabolite and cortisol levels were elevated (P < 0.05) following every PGF2alpha administration. Despite peaks, we saw no changes (P > 0.05) in progesterone levels between the P-group and the C-group. We saw no differences (P > 0.05) in estradiol-17beta levels between the P-group and the C-group. We concluded that PGF2alpha stimulates the hypothalamus-pituitary-adrenal axis, as evidenced by the elevation of cortisol and progesterone but not estradiol-17beta. Furthermore, repeated PGF2alpha administration might be associated with a delayed ova transport and an increased number of accessory spermatozoa bound to the ZP. However, the effect of PGF2alpha on embryo development is unclear.