The effect of oestrogen on uterine plasticity in late pregnant rats

The effect of estrogen on fetal survival in progesterone-treated ovariectomized rats.

“…Similar fetal damage was observed by Kroc et al(1959) on Day21of pregnancy in ovariectomized rats treated with progesterone alone. Intrauterine pressure in ovariectomized pregnant rats treated with progesterone alone was about4times greater than that in intact pregnant rats (Ichikawa and Tamada, 1980). These observations suggest that the bleeding was caused at the critical period by pressing the head or dune of the growing fetuses onto the constriction rings under abnormally high pressure.…”

PATHFAST, a novel chemiluminescent enzyme immunoassay for measuring estradiol in equine whole blood and serum

“…It induces estrus and prepares the uterus for fertilization and implantation by promoting endometrial growth, development of the uterine gland, and secretion of uterine and vaginal mucus [6]. The physiological function of estradiol is to induce embryo implantation in the uterus and maintain uterine conditions for the growing fetus during pregnancy [7,8,9,10,11,12]. Therefore, measurement of estradiol is useful for detecting follicular and placental function in cyclic and pregnant mares.…”

“…Remarkable fetal growth occurs in the uterus during the late stages of pregnancy in all mammals. The most important factor involved includes the rapid elongation and cylindrical changes in the uterus to maintain fetal survival at the stage of rapid fetal growth during the late stages of pregnancy [9,10,11,12]. Progesterone, estrogen, prolactin and relaxin play key roles in the implantation of embryos, maintenance of pregnancy, and induction of parturition.…”

“…Progesterone, estrogen, prolactin and relaxin play key roles in the implantation of embryos, maintenance of pregnancy, and induction of parturition. Although the synergistic action of progesterone and estrogen is generally essential for mares, as in most mammals, for maintaining successful pregnancy, estrogen plays a dominant role in the maintenance of uterine elongation when the fetus grows rapidly in late pregnancy [9,10,11,12]. Therefore, monitoring circulating estradiol and progesterone is useful for detecting clinical signs of abortion, stillbirth, and perinatal fetal death during late pregnancy in mares [19,20,21,22].…”

The effect of ovarian hormones on stress relaxation in the uterus of the pregnant rat.

“…In ovariectomized pregnant rats treated with progesterone, intrauterine pressure in late pregnancy is markedly higher than that in intact pregnant rats (Ichikawa and Tamada, 1980), and fetal injury occurs at the critical period when fetuses change from a spheroidal to a cylindrical shape (Tamada and Ichikawa, 1980). Since treatment with estrogen as well prevents the increase in intrauterine pressure and fetal injury, it has been suggested that estrogen may ensure sufficient plasticity of the uterus to allow for the increase in conceptus size at the critical period.…”