Bacterial Lipopolysaccharide Induces an Endocrine Switch from Prostaglandin F2α to Prostaglandin E2 in Bovine Endometrium

Escherichia coli infection of the endometrium causes uterine disease after parturition and is associated with prolonged luteal phases of the ovarian cycle in cattle. Termination of the luteal phase is initiated by prostaglandin F2α (PGF) from oxytocin-stimulated endometrial epithelial cells. Compared with normal animals, the peripheral plasma of animals with E. coli infection of the endometrium had higher concentrations of lipopolysaccharide (LPS) and prostaglandin E2 (PGE) but not PGF. Endometrial explants accumulated predominantly PGE in the culture medium in response to LPS, and this effect was not reversed by oxytocin. Endometrial cells expressed the Toll-like receptor 4/CD14/MD-2 receptor complex necessary to detect LPS. Epithelial and stromal cells treated with LPS had higher steady-state media concentrations of PGE rather than PGF. Arachadonic acid is liberated from cell membranes by phospholipase 2 (PLA2) enzymes and converted to prostaglandins by synthase enzymes. Treatment of epithelial and stromal cells with LPS did not change the levels of PGE or PGF synthase enzymes. However, LPS stimulated increased levels of PLA2 group VI but not PLA2 group IV C immunoreactive protein in epithelial cells. Endometrial cells expressed the E prostanoid 2 and E prostanoid 4 receptors necessary to respond to PGE, which regulates inflammation as well as being luteotropic. In conclusion, LPS detection by endometrial cells stimulated the accumulation of PGE rather than PGF, providing a mechanism to explain prolonged luteal phases in animals with uterine disease, and this PGE may also be important for regulating inflammatory responses in the endometrium.

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Effect of LH on prostaglandin F2α and prostaglandin E2 secretion by cultured porcine endometrial cells

Reproduction ◽

10.1530/rep.1.00639 ◽

2005 ◽

Vol 130 (1) ◽

pp. 105-112 ◽

Cited By ~ 23

Author(s):

Agnieszka Blitek ◽

Adam J Ziecik

Keyword(s):

Epithelial Cells ◽

Prostaglandin E2 ◽

Stromal Cells ◽

Prostaglandin F2α ◽

Cell Types ◽

Oestrous Cycle ◽

Time Dependent ◽

Dependent Effect ◽

Endometrial Cells ◽

Time Dependent Effect

LH appears to be a potent stimulator of the release of endometrial prostaglandins (PGs) in the pig. The aim of the present studies was to examine the effect of LH on PGF2αand PGE2secretion by cultured porcine endometrial cells on days 10–12 and 14–16 of the oestrous cycle and to compare its action with oxytocin. A time-dependent effect of LH (10 ng/ml) on PGF2αrelease from luminal epithelial and stromal cells on days 10–12 was observed (experiment 1). The highest increase in PGF2αsecretion in response to LH was detected in stromal cells after 6 h of incubation (P< 0.001). Epithelial cells responded to LH after a longer exposure time (P< 0.01). A concentration-dependent effect of LH (0.1–100 ng/ml) on PGF2αrelease from stromal cells was examined after 6 h and from epithelial cells after 12 h (experiment 2). Effective concentrations of LH were 10 and 100 ng/ml. LH (10 ng/ml) and oxytocin (100 nmol/l) affected PGF2αand PGE2secretion from endometrial cells on days 10–12 and 14–16 of the oestrous cycle (experiment 3). LH stimulated PGF2αsecretion from both cell types and its action was more potent on days 10–12. LH induced PGE2release, especially in epithelial cells on days 14–16. A stimulatory effect of oxytocin on PGF2αwas confirmed in stromal cells, but this hormone was also shown to enhance PGE2output. These results indicated that LH, like oxytocin, a very effective stimulator of PGF2αrelease, could play an important role in the induction of luteolysis.

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Bovine herpesvirus 4 is tropic for bovine endometrial cells and modulates endocrine function

Reproduction ◽

10.1530/rep-07-0065 ◽

2007 ◽

Vol 134 (1) ◽

pp. 183-197 ◽

Cited By ~ 57

Author(s):

Gaetano Donofrio ◽

Shan Herath ◽

Chiara Sartori ◽

Sandro Cavirani ◽

Cesidio Filippo Flammini ◽

...

Keyword(s):

Epithelial Cells ◽

Stromal Cells ◽

Bovine Herpesvirus ◽

Endocrine Function ◽

Uterine Disease ◽

Endometrial Stromal Cells ◽

Persistently Infected ◽

Endometrial Cells ◽

Bovine Herpesvirus 4 ◽

Herpesvirus 4

Bovinepostpartumuterine disease, metritis, affects about 40% of animals and is widely considered to have a bacterial aetiology. Although the γ-herpesvirus bovine herpesvirus 4 (BoHV-4) has been isolated from several outbreaks of metritis or abortion, the role of viruses in endometrial pathology and the mechanisms of viral infection of uterine cells are often ignored. The objectives of the present study were to explore the interaction, tropism and outcomes of BoHV-4 challenge of endometrial stromal and epithelial cells. Endometrial stromal and epithelial cells were purified and infected with a recombinant BoHV-4 carrying an enhanced green fluorescent protein (EGFP) expression cassette to monitor the establishment of infection. BoHV-4 efficiently infected both stromal and epithelial cells, causing a strong non-apoptotic cytopathic effect, associated with robust viral replication. The crucial step for the BoHV-4 endometriotropism appeared to be after viral entry as there was enhanced transactivation of the BoHV-4 immediate early 2 gene promoter following transient transfection into the endometrial cells. Infection with BoHV-4 increased cyclooxygenase 2 protein expression and prostaglandin estradiol secretion in endometrial stromal cells, but not epithelial cells. Bovine macrophages are persistently infected with BoHV-4, and co-culture with endometrial stromal cells reactivated BoHV-4 replication in the persistently infected macrophages, suggesting a symbiotic relationship between the cells and virus. In conclusion, the present study provides evidence of cellular and molecular mechanisms, supporting the concept that BoHV-4 is a pathogen associated with uterine disease.

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Expression and Function of Toll-Like Receptor 4 in the Endometrial Cells of the Uterus

Endocrinology ◽

10.1210/en.2005-1113 ◽

2006 ◽

Vol 147 (1) ◽

pp. 562-570 ◽

Cited By ~ 183

Author(s):

Shan Herath ◽

Deborah P. Fischer ◽

Dirk Werling ◽

Erin J. Williams ◽

Sonia T. Lilly ◽

...

Keyword(s):

Epithelial Cells ◽

Stromal Cells ◽

Prostaglandin F2α ◽

Endocrine Function ◽

Toll Like Receptor ◽

Toll Like Receptor 4 ◽

Endometrial Cells ◽

E Coli ◽

Female Sex Hormones ◽

And Function

Prostaglandins have a central role in many endocrine functions in mammals, including regulation of the life span of the corpus luteum by prostaglandin F2α (PGF) and prostaglandin E2 (PGE), which are secreted by the uterine endometrium. However, the uterus is readily infected with bacteria such as Escherichia coli, which disrupt luteolysis. Immune cells detect E. coli by Toll-like receptor 4 (TLR4) binding its pathogenic ligand, lipopolysaccharide (LPS), although signaling requires accessory molecules such as CD14. The objective of this study was to determine the effect of E. coli or LPS on the function of bovine endometrial cells, and whether purified populations of epithelial and stromal cells express the molecules involved in LPS recognition. In addition, because the female sex hormones estradiol and progesterone modify the risk of uterine infection, their effect on the LPS response was investigated. Endometrial explants produced prostaglandins in response to LPS, with an increased ratio of PGE to PGF. Addition of LPS or E. coli to stromal and epithelial cells stimulated production of PGE and PGF and increased their cyclooxygenase 2 mRNA expression. The production of prostaglandins was abrogated by an LPS antagonist. In addition, estradiol and progesterone inhibited the production of PGE and PGF in response to LPS, indicating a role for steroid hormones in the response to bacterial infection. For the first time, Toll-like receptor 4 mRNA and CD14 mRNA and protein were detected in bovine endometrial stromal and epithelial cells by RT-PCR and flow cytometry. In conclusion, epithelial and stromal cells detect and respond to bacteria, which modulate their endocrine function.

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Effect of ovarian steroids on basal and oxytocin-induced prostaglandin F2α secretion from pig endometrial cells

Reproduction Fertility and Development ◽

10.1071/rd03024 ◽

2003 ◽

Vol 15 (4) ◽

pp. 197 ◽

Cited By ~ 9

Author(s):

Jianbo Hu ◽

Gheorghe T. Braileanu ◽

Mark A. Mirando

Keyword(s):

Epithelial Cells ◽

Stromal Cells ◽

Chronic Treatment ◽

Prostaglandin F2α ◽

Exocrine Secretion ◽

Apical Surface ◽

Stimulatory Action ◽

Endometrial Cells ◽

Oestradiol Treatment ◽

Luminal Epithelial Cells

These studies were undertaken to determine how treatment with 100 nM progesterone and/or 10 nM oestradiol-17β acutely (3 h; Experiment 1) or chronically (72 h; Experiments 2–4) influenced basal and oxytocin (OT)-stimulated prostaglandin (PG) F2α secretion, in enriched cultures of pig endometrial luminal epithelial, glandular epithelial and stromal cells obtained on Day 16 (Experiments 1, 2 and 4) or Day 12 (Experiment 3) after oestrus. In Experiment 1, acute treatment with progesterone stimulated PGF2α secretion from each cell type on Day 16, whereas acute oestradiol treatment inhibited the stimulatory action of progesterone on PGF2α secretion only in glandular epithelial cells. In Experiment 2, OT stimulated phospholipase (PL) C activity in luminal epithelial cells on Day 16 only in the presence of chronic oestradiol treatment. For glandular epithelial cells on Day 16, OT stimulated PLC activity only in the presence of chronic treatment with steroid. In stromal cells on Day 16, OT stimulated PLC activity in the absence of steroids and the response to OT was further enhanced by oestradiol. In the absence of chronic treatment with steroid, OT did not stimulate PGF2α secretion from luminal epithelial cells, but oestradiol induced a response to OT. For glandular epithelial cells, OT-induced PGF2α secretion was not altered by steroids, whereas the stimulatory response to OT was inhibited by oestradiol or progesterone in stromal cells. For endometrial cells obtained on Day 12 after oestrus in Experiment 3, OT only stimulated PGF2α release from glandular epithelial and stromal cells. For luminal epithelial cells obtained on Day 16 after oestrus and cultured under polarizing conditions in Experiment 4, secretion of PGF2α occurred preferentially from the basolateral surface and was stimulated by OT more from the basolateral surface than from the apical surface. Oxytocin-induced PGF2α secretion from the apical surface was enhanced by chronic treatment with oestradiol, whereas that from the basolateral surface was enhanced by chronic treatment with progesterone. In summary, oestradiol enhanced OT-induced PGF2α secretion from the apical surface of luminal epithelial cells and reduced the response of stromal cells to OT, actions that may contribute to the reorientation of PGF2α from endocrine secretion (i.e. towards the uterine vasculature) to exocrine secretion (i.e. towards the uterine lumen) during pregnancy recognition in pigs.

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Molecular Cloning and Characterization of Prostaglandin (PG) Transporter in Ovine Endometrium: Role for Multiple Cell Signaling Pathways in Transport of PGF2α

Endocrinology ◽

10.1210/en.2007-1087 ◽

2007 ◽

Vol 149 (1) ◽

pp. 219-231 ◽

Cited By ~ 31

Author(s):

S. K. Banu ◽

J. Lee ◽

M. C. Satterfield ◽

T. E. Spencer ◽

F. W. Bazer ◽

...

Keyword(s):

Protein Kinase ◽

Epithelial Cells ◽

Estrous Cycle ◽

Molecular Mechanisms ◽

Growth Factor Receptor ◽

Prostaglandin F2α ◽

Cellular Transport ◽

Endometrial Cells ◽

Amino Terminal ◽

Endometrial Epithelial Cells

In ruminants, endometrial prostaglandin F2α (PGF2α) is the luteolytic hormone. Cellular transport of PGF2α in the uterine endometrium is critical for regulation of the estrous cycle. Molecular mechanisms responsible for control of PGF2α transport in endometrium during luteolysis are largely unknown. In the present study, we characterized the prostaglandin transporter (PGT) in ovine endometrium. Ovine PGT cDNA consists of 1935 nucleotides that encode 644 amino acids. In ovine endometria, PGT is highly expressed during the period of luteolysis, between d 14 and 16 of the estrous cycle, in luminal and glandular epithelia. Pharmacological and genomic inhibition of PGT indicates that it is responsible for influx and efflux of PGF2α in ovine endometrial epithelial cells. Inhibition of PGT during the period of luteolysis prevents the release of oxytocin-induced PGF2α pulses, and maintains functional corpus luteum and its secretion of progesterone. In ovine endometrial epithelial cells, protein kinase A and protein kinase C pathways are involved in regulating the influx of PGF2α, whereas epidermal growth factor receptor pathways are implicated in regulation of influx and efflux of PGF2α. The ERK1/2 pathway is associated with efflux of PGF2α, whereas Jun-amino-terminal kinase/stress-activated protein kinase pathways are involved in both efflux and influx of PGF2α. Phosphatidylinositol 3-kinase pathways are not involved in either influx or efflux of PGF2α in ovine endometrial epithelial cells. These are the first results to demonstrate a functional role for PGT in regulation of PGF2α efflux and influx in ovine endometrial cells that influence luteolytic mechanisms in ruminants.

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Ovarian steroids affect prostaglandin production in equine endometrial cells in vitro

Journal of Endocrinology ◽

10.1530/joe-13-0185 ◽

2014 ◽

Vol 220 (3) ◽

pp. 263-276 ◽

Cited By ~ 12

Author(s):

Anna Z Szóstek ◽

António M Galvão ◽

Graça M Ferreira-Dias ◽

Dariusz J Skarzynski

Keyword(s):

Cell Proliferation ◽

Epithelial Cells ◽

Protein Expression ◽

Stromal Cells ◽

Positive Control ◽

Dependent Manner ◽

Ovarian Steroids ◽

Endometrial Cells ◽

Prostaglandin Endoperoxide Synthase

This study aimed to evaluate the influence of ovarian steroids on equine endometrial epithelial and stromal cells, specifically i) prostaglandin (PG) production in a time-dependent manner, ii) specific PG synthases mRNA transcription and protein expression, and iii) cell proliferation. After passage I, cells were exposed to vehicle, oxytocin (OT, positive control, 10−7M), progesterone (P4, 10−7M), 17β estradiol (E2, 10−9M), or P4+E2for 12, 24, 48, or 72 h. Following treatment, PG concentration was determined using the direct enzyme immunoassay (EIA) method. Alterations inPGsynthases mRNA transcriptions,PGsynthases protein expression, and cell proliferation in response to the treatments were determined after 24 h using real-time PCR, western blot, or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide respectively. After 24 h, E2and P4+E2increased PGE2and PGF2αsecretion as well as specific prostaglandin-endoperoxide synthase-2 (PTGS2), PGE2synthases (PGES), and PGF2αsynthases (PGFS) expression in the epithelial cells (P<0.05). Additionally, E2and P4+E2increased PTGS2 expression in stromal cells after 24 h (P<0.05). In stromal cells, P4+E2increased PGE2production as well as PGES expression after 24 h (P<0.05). Both E2and P4+E2increased PGF2αproduction by stromal cells after 24 h (P<0.05). Ovarian steroids affected proliferation of stromal and epithelial cells during the 24-h incubation period (P<0.05). We provide evidence that ovarian steroids affect PG production in equine endometrial cells, upregulating PTGS2, PGES, and PGFS expression. Ovarian steroid-stimulated PG production could be an important mechanism occurring in the equine endometrium that is involved in the regulation of the estrous cycle and early pregnancy.

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Epithelial and Stromal Cells of Bovine Endometrium Have Roles in Innate Immunity and Initiate Inflammatory Responses to Bacterial Lipopeptides In Vitro via Toll-Like Receptors TLR2, TLR1, and TLR6

Endocrinology ◽

10.1210/en.2013-1822 ◽

2014 ◽

Vol 155 (4) ◽

pp. 1453-1465 ◽

Cited By ~ 67

Author(s):

Matthew L. Turner ◽

James G. Cronin ◽

Gareth D. Healey ◽

Iain Martin Sheldon

Keyword(s):

Stromal Cells ◽

Small Interfering Rna ◽

Inflammatory Responses ◽

Nuclear Factor Κb ◽

Cell Surface Receptor ◽

Nuclear Factor ◽

Endometrial Cells ◽

Wide Range ◽

Rna Targeting ◽

Interfering Rna

Bacteria often infect the endometrium of cattle to cause endometritis, uterine disease, and infertility. Lipopeptides are commonly found among bacteria and are detected by the Toll-like receptor (TLR) cell surface receptor TLR2 on immune cells. Heterodimers of TLR2 with TLR1 or TLR6 activate MAPK and nuclear factor-κB intracellular signaling pathways to stimulate inflammatory responses. In the endometrium, epithelial and stromal cells are the first to encounter invading bacteria, so the present study explored whether endometrial cells can also mount inflammatory responses to bacterial lipopeptides via TLRs. The supernatants of pure populations of primary bovine endometrial epithelial and stromal cells accumulated the cytokine IL-6 and the chemokine IL-8 in response to triacylated or diacylated bacterial lipopeptides. The accumulation of IL-6 and IL-8 in response to triacylated lipopeptides was reduced by small interfering RNA targeting TLR2 or TLR1 but not TLR6, whereas cellular responses to diacylated lipopeptide were reduced by small interfering RNA targeting TLR2, TLR1, or TLR6. Both lipopeptides induced rapid phosphorylation of ERK1/2, p38, and nuclear factor-κB in endometrial cells, and inhibitors of ERK1/2 or p38 limited the accumulation of IL-6. The ovarian steroids estradiol and progesterone had little impact on inflammatory responses to lipopeptides. The endometrial epithelial and stromal cell responses to lipopeptides via TLR2, TLR1, and TLR6 provide a mechanism linking a wide range of bacterial infections to inflammation of the endometrium.

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Oxytocin-stimulated phosphoinositide hydrolysis and prostaglandin F2α secretion by luminal epithelial, glandular epithelial and stromal cells from pig endometrium. II. Responses of cyclic, pregnant and pseudopregnant pigs on Days 12 and 1

Reproduction Fertility and Development ◽

10.1071/rd00084 ◽

2000 ◽

Vol 12 (4) ◽

pp. 157 ◽

Cited By ~ 14

Author(s):

Mehmet Uzumcu ◽

Kevin G. Carnahan ◽

Gheorghe T. Braileanu ◽

Mark A. Mirando

Keyword(s):

Epithelial Cells ◽

Early Pregnancy ◽

Stromal Cells ◽

Prostaglandin F2α ◽

Secretory Response ◽

Reproductive Status ◽

Phosphoinositide Hydrolysis ◽

Pregnancy Recognition ◽

Luminal Epithelial Cells

In pigs, the exact mechanism for the shift in endometrial PGF 2α secretion from an endocrine to an exocrine mode during pregnancy recognition is not known. The objective of this study was to examine whether this shift involved a change in the responsiveness of luminal epithelial, glandular epithelial and stromal cells to 0 or 100 nM oxytocin. Luminal epithelial cells, glandular epithelial cells and stromal cells were isolated from cyclic, pregnant or oestrogen-induced pseudopregnant gilts on Day 12 (Experiment 1) or Day 16 (Experiment 2) post oestrus (oestrus = Day 0). For cells obtained on Day 12, oxytocin stimulated PGF2α secretion by stromal cells (P<0.01) similarly for each reproductive status, whereas oxytocin stimulated PGF 2α secretion from luminal and glandular epithelial cells (P<0.05) from pregnant and pseudopregnant gilts but not from cyclic gilts. For both concentrations of oxytocin, mean PGF2α secretion was less (P<0.05) from stromal cells of pregnant than cyclic gilts. For cells obtained on Day 16, oxytocin stimulated PGF 2α release from stromal cells of cyclic gilts but not from stromal cells of pregnant gilts. Mean PGF 2α secretion also was less (P<0.05) from stromal cells of pregnant gilts than cyclic gilts. Oxytocin tended to stimulate PGF 2α release (P<0.07) from glandular epithelial cells of cyclic but not pregnant or pseudopregnant gilts. Luminal epithelial cells from all reproductive statuses were similarly unresponsive to oxytocin. In conclusion, the increased PGF2α secretory response to oxytocin of luminal and glandular epithelial cells from pregnant gilts on Day 12, combined with the decreased response of stromal cells from pregnant gilts on Days 12 and 16, may contribute, in part, to the shift in endometrial PGF2α secretion from an endocrine to an exocrine direction during early pregnancy in pigs.

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Endometrial Stromal Cells Circulate in the Bloodstream of Women with Endometriosis: A Pilot Study

International Journal of Molecular Sciences ◽

10.3390/ijms20153740 ◽

2019 ◽

Vol 20 (15) ◽

pp. 3740 ◽

Cited By ~ 3

Author(s):

Júlia Vallvé-Juanico ◽

Carlos López-Gil ◽

Agustín Ballesteros ◽

Xavier Santamaria

Keyword(s):

Pilot Study ◽

Epithelial Cells ◽

Stromal Cells ◽

Diagnostic Tools ◽

Pelvic Cavity ◽

Endometrial Stromal Cells ◽

Endometrial Cells ◽

Retrograde Menstruation ◽

The Brain ◽

Endometrial Epithelial Cells

Endometriosis is characterized by the presence of endometrial tissue outside the uterus. While endometriotic tissue is commonly localized in the pelvic cavity, it can also be found in distant sites, including the brain. The origin and pathophysiology of tissue migration is poorly understood; retrograde menstruation is thought to be the cause, although the presence of endometrium at distant sites is not explained by this hypothesis. To determine whether dissemination occurs via the bloodstream in women with endometriosis, we analyzed circulating blood for the presence of endometrial cells. Circulating endometrial stromal cells were identified only in women with endometriosis but not in controls, while endometrial epithelial cells were not identified in the circulation of either group. Our results support the hypothesis that endometrial stromal cells may migrate through circulation and promote the pathophysiology of endometriosis. The detection of these cells in circulation creates avenues for the development of less invasive diagnostic tools for the disease, and opens possibilities for further study of the origin of endometriosis.

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Effects of arginine- and lysine-vasopressin on phospholipase C activity, intracellular calcium concentration and prostaglandin F2alpha secretion in pig endometrial cells

Reproduction ◽

10.1530/rep.0.1210605 ◽

2001 ◽

pp. 605-612 ◽

Cited By ~ 9

Author(s):

GT Braileanu ◽

SM Simasko ◽

J Hu ◽

A Assiri ◽

MA Mirando

Keyword(s):

Epithelial Cells ◽

Intracellular Calcium ◽

Phospholipase C ◽

Arginine Vasopressin ◽

Stromal Cells ◽

Calcium Concentration ◽

Intracellular Calcium Concentration ◽

Endometrial Cells ◽

Lysine Vasopressin ◽

Luminal Epithelial Cells

Oxytocin and vasopressin are related peptides that have receptors in the uterus. Species from families other than Suidae produce only arginine-vasopressin; in contrast, pigs apparently express both arginine- and lysine-vasopressin. The aim of this study was to determine whether arginine- or lysine-vasopressin would activate phospholipase C, increase intracellular calcium concentration [Ca(2+)](i) and stimulate PGF(2alpha) production in enriched cultures of stromal, glandular epithelial and luminal epithelial cells from pig endometrium. Cells were obtained from gilts on day 16 after oestrus by differential enzymatic digestion and sieve separation. After 96 h in culture, the cells were treated with 0 or 100 nmol arginine- or lysine-vasopressin l(-1). The responses to 100 nmol oxytocin l(-1) and 100 nmol GnRH l(-1) were used as positive and negative controls, respectively. Consistent with previous results, oxytocin stimulated phospholipase C activity (P < 0.05), increased [Ca(2+)](i) (P < 0.05) and promoted PGF(2alpha) secretion (P < 0.05) from stromal and glandular epithelial cells. Activity of phospholipase C, [Ca(2+)](i) and PGF(2alpha) release were also increased (P < 0.05) by arginine-vasopressin in stromal cells, but the responses were less (P < 0.01) than those induced by oxytocin. An oxytocin antagonist attenuated the [Ca(2+)](i) response of stromal cells to both oxytocin and arginine-vasopressin. Sequential treatment of cells with oxytocin and arginine-vasopressin indicated that oxytocin desensitized the response to oxytocin, but arginine-vasopressin did not similarly desensitize the response to oxytocin. In glandular and luminal epithelial cells, arginine-vasopressin did not stimulate phospholipase C activity, [Ca(2+)](i) or PGF(2alpha) secretion. Neither GnRH nor lysine-vasopressin induced phospholipase C activity, increased [Ca(2+)](i) or stimulated PGF(2alpha) production in any endometrial cell type. These results indicate that oxytocin receptors can bind arginine-vasopressin more readily than they bind lysine-vasopressin. Type 1 vasopressin receptors may also exist in endometrium predominantly on cells other than stromal, glandular epithelial and luminal epithelial cells, as in previous studies both arginine-vasopressin and lysine-vasopressin stimulated phospholipase C activity in endometrial explants to a similar extent as oxytocin.

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