Effect of pregnancy on endometrial expression of luteolytic pathway components in the mare.
Prostaglandins produced by the intrauterine tissues of both mother and fetus (myometrium, decidua, placenta, chorion, and amnion) are involved with all of the physiologies of parturition (membrane rupture, cervical dilatation, myometrial contractility, placental separation, and uterine involution). For parturition to occur, however, the intrauterine tissues need to first be activated to prepare for the work of labor, then stimulated to initiate labor. Prostaglandins normally are considered to be stimulators of the physiologies of labor. This review presents evidence that one prostaglandin, PGF2alpha, and its receptor, FP, are also activators, especially of the decidua. Stimulated by cytokines, the decidual synthesis of PGF2alpha and the expression of FP lead to increased matrix metalloproteinase activity, further enhancement of cytokine activity, increased decidual oxytocin and oxytocin receptor expression, decreased progesterone responsiveness, and possibly, enhanced expression of vascular endothelial growth factor. These collective actions prepare the decidua for its role in parturition.