Secretory Function of the Ovine Uterus: Effects of Gestation and Steroid Replacement Therapy

Abstract

In Exp. 1, changes in uterine fluid content of protein, calcium and prostaglandin F2 alpha (PGF) were examined between d 30 to 144 of gestation. Volume of uterine fluid (mean +/- SE) in the nongravid uterine horn of unilaterally pregnant ewes increased (P less than .05) between d 30 (8 +/- 1 ml) and d 144 (749 +/- 46 ml) of gestation. Protein concentration and total protein in uterine fluid also increased (P less than .05) between d 30 (2.3 +/- .4 mg/ml; 19 +/- 7 mg) and d 144 (23.5 +/- 3.3 mg/ml; 17.4 +/- 2.0 g). Total recoverable calcium (mg) in secretions increased from .1 mg (d 30) to over 1.4 g (d 144) due to day of gestation effects (P less than .05). Total PGF also increased (P less than .01) from 7 ng on d 30 to 15.7 g on d 144. In Exp. II, ovariectomized (OVX) ewes were treated with either corn oil, estrone (E), progesterone (P) or P+E (PE) for 30 d. Treatment with P or PE increased calcium concentration and content (P less than .01) in secretions, but differences in uterine fluid volumes and concentrations of protein and PGF were not significant. Treatment of OVX ewes with P stimulated (P less than .05) in vitro synthesis of secretory proteins by endometrium, whereas treatment with E enhanced release of unlabeled proteins (P less than .05). The major endometrial secretory proteins were identified in allantoic fluids from d 60 to term and were detected along the mesenchymal border of the chorioallantois using immunohistochemistry. Results from this study indicate that P may be a primary hormone regulating accumulation of fluid, protein, calcium and specific endometrial proteins in the uterine lumen during gestation, and that uterine milk proteins gain access to the fetal-placental unit.

Galectin-15 in ovine uteroplacental tissues

“…These results support the idea that galectin-15 protein is synthesized by the endometrial LE and sGE and then secreted into the uterine lumen, where it is absorbed by the placenta, transported into the fetal circulation, and cleared by the kidney into the allantois via the urachus (Bazer 1975, Roberts & Bazer 1988. Although the allantois was initially considered a reservoir for waste products of the fetus, it serves to store most secreted proteins from the endometrium (Bazer et al 1975, Moffatt et al 1987). In contrast, amniotic fluid is not in the path for protein clearance by the fetal kidney and, therefore, does not function in this capacity.…”

“…Histotroph is a rather undefined, complex mixture of adhesion proteins, transport proteins, ions, growth factors, hormones, proteases, protease inhibitors, amino acids and other molecules (Bazer 1975, Roberts & Bazer 1988. Uterine secretions are of particular importance for conceptus survival and growth in domestic animals due to their protracted peri-implantation period and non-invasive types of placentation (Bazer 1975, Roberts et al 1987, Roberts & Bazer 1988. Indeed, histotroph is absorbed by the placenta, transported into the fetal circulation and cleared by the kidney into the allantois via the urachus (Bazer 1975, Roberts & Bazer 1988.…”

2 Identification of Genes Induced by the Conceptus in the Bovine Endometrium During the Pre-Implantation Period

“…Production of a protein similar to UTMP was also noted in the uterus of a pregnant cow. Treatment of ovariectomized ewes with estrogens does not lead to enhanced presence of UTMP in uterine secretion (Moffatt et al, 1987). The findings of Bauersachs and coworkers (2005), however, contradict the common view that the expression of UTMP is directly stimulated by progesterone.…”

“…There are hints that progesterone is the primary hormone regulating accumulation of fluid, protein, calcium, and specific endometrial proteins in the uterine lumen during gestation (Moffatt et al, 1987). The two best characterized glandular epithelium secretory products are the uterine milk protein and osteopontin.…”

Progesterone and interferon tau regulate leukemia inhibitory factor receptor and IL6ST in the ovine uterus during early pregnancy

“…The increase in endometrial LIFR expression by early treatment with P4 in study 2 also occurred coincident with early loss of PGR by endometrial LE/sGE (Satterfield et al 2006). Similarly, IL6ST is expressed predominantly in endometrial GE as is the case for secreted phosphoprotein 1 (commonly referred to as osteopontin), serpin peptidase inhibitor (also known as uterine milk protein or UTMP), stanniocalcin 1 (STC1), and GRP, which encode proteins secreted into the uterine lumen (Moffatt et al 1987, Ing & Roberts 1989, Johnson et al 1999b, Song et al 2006b, 2008b). All four of those genes are induced in endometrial GE by the long-term effects of continuous P4 that also requires loss of the PGR as a permissive event preceding IFNT effects to enhance gene expression (Spencer & Bazer 2002, Spencer et al 2004b.…”