Prostaglandin E2 (PGE2) inhibits an IUD-induced premature luteolysis in sheep

Fifteen ewes were assigned as they came into estrus to one of three randomized treatment groups: 1. Sham IUD + Vehicle, 2. IUD + Vehicle, and 3. IUD + PGE2 in Vehicle. An IUD was inserted adjacent to the luteal-bearing ovary of unilaterally ovariectomized ewes on day 3 postestrus. Vehicle (Na2CO3) or PGE2 (500 micrograms) in vehicle was given every 4 hours intrauterine through an indwelling uterine cannula from day 3 postestrus until ewes returned to estrus. Luteolysis was advanced in both the Sham IUD and IUD groups receiving vehicle. An IUD-induced premature luteolysis was prevented by PGE based on daily concentrations of progesterone in peripheral blood and the extended interestrous interval. It is concluded that chronic intrauterine injections of PGE2 (500 micrograms) every four hours can prevent an IUD-induced premature luteolysis. It is also concluded that an IUD-induced premature luteolysis is not necessarily through uterine distention.