The effect of a progesterone-releasing intrauterine contraceptive device on uterine secretion of prostaglandin F2alpha and life-span of corpora lutea in the ewe.

Two studies were conducted to investigate the effect of a progesterone-releasing intrauterine contraceptive device (IUD) on uterine secretion of prostaglandin (PG) F2alpha associated with IUD-induced luteolysis in sheep. In bilaterally ovulating ewes receiving an IUD on day 3 (estrus = day 0) intrauterine release of progesterone (90 microgram per day) by the device did not prevent premature luteolysis or the increased concentration of PGF2alpha in uterine venous plasma on day 5 caused by conventional IUD's. In the second study a progesterone-releasing IUD (645 microgram per day) inserted adjacent to the intact ovary at unilateral ovariectomy on day 14 inhibited early luteolysis in the subsequent estrous cycle and reduced the uterine secretion of PGF2alpha on day 5, without affecting concentrations of progesterone in the peripheral circulation at the intervening estrus. It is suggested that locally delivered intrauterine progesterone can inhibit IUD-induced luteolysis in the ewe by suppressing the uterine secretion of PGF2alpha.