Effects of 8-epi-prostaglandin F2 and prostaglandin F2 on serum progesterone concentration and corpus luteum size in ewes

Abstract

Prostaglandin F2 (PGF2 ) is luteolytic in sheep. This study assessed luteolytic ability of an isomer, 8-epi-PGF2 . 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 -PGF2 or PGF2 , 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
PGF2 on day 9, but recovered to control levels (P = 0.646) by day 10. Interestingly, 8-epi-PGF2 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 PGF2, 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-PGF2 (P = 0.032) and PGF2 (P = 0.015). One-time, intra-ovarian administration of 8-epi-PGF2 at this dosage
did not cause luteolysis. Additionally, serum progesterone is capable of recovery from one-time, intra-ovarian
administration of PGF2.