Effects of 8-epi-prostaglandin F2α and prostaglandin F2α on serum progesterone concentration and corpus luteum size in ewes

Prostaglandin F2α (PGF2α) is luteolytic in sheep. This study assessed luteolytic ability of an isomer, 8- epi-PGF2α. Ten ewes were estrus-synchronized and blood serum was collected for 12 days and analyzed for progesterone concentration. Ewes were laparoscopically administered 200 μg 8-epi-PGF2αor PGF2α, or placebo in each ovary on day 8 and ovariectomized on day 13. Corpora lutea (CL) were weighed. Serum progesterone was reduced (P < 0.041) by PGF2α on day 9, but recovered to control levels (P = 0.646) by day 10. Interestingly, 8-epi-PGF2α increased (P < 0.050) serum progesterone on days 9, 10, and 12. However, area under curve for serum progesterone between days 8 and 12 did not differ (P = 0.165) among treatments. In ewes administered PGF2α, serum progesterone decreased sharply (P < 0.001) after treatment, but recovered (P = 0.217) to pre treatment levels by day 11, indicating limited luteolysis after one-time dosage. Mean CL weight did not differ (P = 0.836) among treatments, but weight of largest CL was reduced by 8-epi-PGF2α (P = 0.032) and PGF2α (P = 0.015). One-time, intraovarian administration of 8-epi-PGF2α at this dosage did not cause luteolysis. Additionally, serum progesterone is capable of recovery from one-time, intra-ovarian administration of PGF2α.