6-Keto-prostaglandin E1 and the decidual cell reaction in rats

Although there is considerable evidence that prostaglandins (PGs) are involved in the decidual cell reaction in rats, which PGs are involved is uncertain. In the present study, we investigated the possibility that 6-keto-PGE1 is involved. To determine its ability to induce decidualization, 6-keto-PGE1 was infused unilaterally from Alzet osmotic minipumps into the uterine lumen of ovariectomized rats treated with estrogen and progesterone to sensitize their uteri for the decidual cell reaction. To reduce endogenous PG production, indomethacin was injected 2-3 h prior to pump insertion and was included in the vehicle for PG infusion. As determined by uterine weights 5 days after pump insertion, 6-keto-PGE1 and PGE2 produced decidualization which was equivalent. As indicated by a dose-response study, 6-keto-PGE1 and PGE2 did not differ in their ability to bring about decidualization. To determine if a deciduogenic stimulus resulted in increased uterine production of 6-keto-PGE1, as assessed by uterine concentrations, 6-keto-PGE1 and PGE concentrations in the uterus were determined after the unilateral intrauterine injection of 100 microliters sesame oil. There were no significant differences between stimulated and non-stimulated horns in 6-keto-PGE1 concentrations, whereas the concentrations of PGE2 were elevated in the stimulated horns. These data indicate that while both exogenous 6-keto-PGE1 and PGE2 induce decidualization, only uterine PGE concentrations are elevated by deciduogenic stimuli. Thus it is unlikely that 6-keto-PGE1 plays a role in decidualization.