Induction of Decidualization in Rats by the Intrauterine Infusion of Prostaglandins1

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Abstract
Alzet osmotic minipumps, attached to the ovarian end of the uterine horn, were used to infuse prostaglandins [PG] unilaterally into the uterine lumen of mature ovariectomized rats treated with a regimen of estradiol and progesterone to sensitize the uteri for the decidual cell reaction. The rats were treated with indomethacin prior to the insertion of the pumps to inhibit endogenous PG production. Decidualization was assessed 4 days later by determining uterine weights and by histological examination; the geometric mean weight of horns infused with vehicle (1 .mu.l/h) was 332 mg, significantly less than those of horns infused with PGE2 (1 .mu.g/h), PGF2.alpha. (1 .mu.g/h) or combined PGE2 and F2.alpha. (geometric means of 939, 763 and 1114 mg, respectively). To determine if PG synthesis is required throughout the poststimulus period to obtain full decidualization, rats were given a single injection of 2 mg indomethacin either 2 h before or 12, 24 or 48 h after the deciduogenic stimulus, a unilateral intrauterine injection of 50 .mu.l sesame oil. As assessed by uterine weights 4 days later, decidualization was reduced by indomethacin treatment. In the stimulated (compared to the nonstimulated) horns, uterine concentrations of PGE and PGF were markedly elevated 5 min after intraluminal oil but returned to concentrations which were not significantly higher by 6 h and 24 h, respectively. Apparently, PG are involved throughout the transformation of endometrial stromal cells to decidual cells in rats.