Uterine PGE Research Articles

Analysis of the uterine lumen in fertility-classified heifers: I. Glucose, prostaglandins, and lipids†.

Survival and growth of the bovine conceptus (embryo and associated extraembryonic membranes) are dependent on endometrial secretions or histotroph found in the uterine lumen. Previously, serial embryo transfer was used to classify heifers as high fertile (HF), subfertile (SF), or infertile (IF). Here, we investigated specific histotroph components [glucose, prostaglandins (PGs), and lipids] in the uterine lumen of day 17 pregnant and open fertility-classified heifers. Concentrations of glucose in the uterine lumen were increased by pregnancy but did not differ among fertility-classified heifers. Differences in expression of genes encoding glucose transporters and involved with glycolysis and gluconeogenesis were observed between conceptuses collected from HF and SF heifers. In the uterine lumen, PGE2 and PGF2α were increased by pregnancy, and HF heifers had higher concentrations of PGE2, PGF2α, and 6-keto-PFG1α than SF heifers. Differences were found in expression of genes regulating PG signaling, arachidonic acid metabolism, and peroxisome proliferator-activated receptor signaling among conceptuses and endometrium from fertility-classified heifers. Lipidomics was conducted exclusively in samples from HF heifers, and phosphatidylcholine was the main lipid class that increased in the uterine lumen by pregnancy. Expression of several lipid metabolism genes differed between HF and SF conceptuses, and a number of fatty acids were differentially abundant in the uterine lumen of pregnant HF and SF heifers. These results support the ideas that uterine luminal histotroph impacts conceptus survival and programs its development and is a facet of dysregulated conceptus-endometrial interactions that result in loss of the conceptus in SF cattle during the implantation period of pregnancy establishment.

Inhibition of luteolysis and embryo-uterine interactions during the peri-implantation period in pigs

Inhibition of luteolysis and establishment of pregnancy in pigs results from oestrogen secretion by the conceptuses and requires progesterone produced by the corpus luteum (CL). An integral part of maternal recognition of pregnancy in the pig is the redirection of prostaglandin (PG) F2alpha secretion from endocrine (blood) to exocrine (uterus) direction and an increase of PGE2 synthesis in both the endometrium and conceptus. Uterine and conceptus PGE2 synthases play an integrated role in establishing the PGE2:PGF2alpha ratio necessary for luteal maintenance. The luteolytic or luteotrophic changes in the CL are synchronised with the release of maternal pituitary and ovarian hormones. The presence of uterine oxytocin (OT) and luteinising hormone (LH) receptors are important for the luteolytic effect of PGF2alpha. Conceptus oestrogen secretion coincides with autocrine and paracrine dialogue between the multiple conceptuses and uterine biological compounds and their receptors in trophoblast and endometrium.

Long chain polyunsaturated fatty acids alter oxytocin signaling and receptor density in cultured pregnant human myometrial smooth muscle cells.

Epidemiological studies and interventional clinical trials indicate that consumption of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) such as docosahexaenoic acid (DHA) lengthen gestational duration. Although the mechanisms are not well understood, prostaglandins (PG) of the 2-series are known to play a role in the initiation and progress of labor. In animal studies, modest DHA provision has been shown to reduce placental and uterine PGE2 and PGF2α, matrix metalloproteinase (MMP)-2 and MMP-9 expression, and placental collagenase activity. However, modulation of PG biosynthesis may not account for all the effects of LC n-3 PUFAs in labor. We investigated one potential PG-independent mechanism of LC PUFA action using cultured pregnant human myometrial smooth muscle cells. Our goal was to characterize the effect of LC PUFA treatment on oxytocin signaling, a potent uterotonic hormone involved in labor. The addition of 10 µM–100 µM DHA or arachidonic acid (AA) to the culture media for 48 h resulted in dose dependent enrichment of these fatty acids in membrane lipid. DHA and AA significantly inhibited phosphatidylinositol turnover and [Ca2+]i mobilization with oxytocin stimulation compared to bovine serum albumin control and equimolar oleic acid. DHA and AA significantly reduced oxytocin receptor membrane concentration without altering binding affinity or rate of receptor internalization. These findings demonstrate a role for LC n-3 PUFAs in regulation of oxytocin signaling and provide new insight into additional mechanisms pertaining to reports of dietary fish and fish oil consumption prolonging gestation.

Transient β2-Adrenoceptor Activation Confers Pregnancy Loss by Disrupting Embryo Spacing at Implantation

Pregnancy loss is a serious social and medical issue, with one important cause associated with aberrant embryo implantation during early pregnancy. However, whether and how the process of embryo implantation is affected by environmental factors such as stress-induced sympathetic activation remained elusive. Here we report an unexpected, transient effect of β2-adrenoreceptor (β2-AR) activation (day 4 postcoitus) in disrupting embryo spacing at implantation, leading to substantially increased midterm pregnancy loss. The abnormal embryo spacing could be prevented by pretreatment of β2-AR antagonist or genetic ablation of β-AR. Similar β2-AR activation at day 5 postcoitus, when implantation sites have been established, did not affect embryo spacing or pregnancy outcome, indicating that the adverse effect of β2-AR activation is limited to the preimplantation period before embryo attachment. In vitro and in vivo studies demonstrated that the transient β2-AR activation abolished normal preimplantation uterine contractility without adversely affecting blastocyst quality. The contractility inhibition is mediated by activation of the cAMP-PKA pathway and accompanied by specific down-regulation of lpa3, a gene previously found to be critical for uterine contraction and embryo spacing. These results indicated that normal uterine contraction-mediated correct intrauterine embryo distribution is crucial for successful ongoing pregnancy. Abnormal β2-AR activation at early pregnancy provided a molecular clue in explaining how maternal stress at early stages could adversely affect the pregnancy outcome.

Effect of cyclooxygenase on “window of implantation” in mouse

The major determinants of uterine receptivity are the ovarian progesterone and estrogen hormones, respectively. Different prostaglandins (PGs) have been elucidated in reproduction and also in this process of implantation in various ways. The blastocyst undergoes implantation on the uterine epithelium in defined hormone prepared period known as “implantation window”. However, any definitive role of PGs in the window of receptivity remains elusive. It is demonstrated herein that selective COX1 inhibitor (SC560) and selective COX2 inhibitor (nimesulide) separately had no significant effect on blastocyst implantation while combination of both inhibitors in lower dose showed partial delay in implantation by more than 24 h and became implanted beyond the window of implantation, i.e. on D6 but these implantation sites were significantly reduced on D10 and the pregnancy is lost in significant number. However, the higher doses of inhibitors in combination completely prevented implantation. Embryos retrieved from these treated mice showed significantly lower number of embryonic cells (77±3.3 and 65.2±3.9) than the optimum number of embryonic cells (93.4±2.6). The lower doses of both the inhibitors reduced uterine PGE 2 and PGI 2 content on D5 but did not inhibit as efficiently as higher doses. In addition, our immunohistochemistry result shows that there was no COX1 and COX2 localization on D5 of treated mice but COX2 begins expressing on D6 like normal D5 of pregnancy. Therefore, we can conclude that embryos implanted after the delay showed defective post-implantation development because of lower number of embryonic cells of implanting blastocyst and implantation beyond the proper time in window of receptivity.

Prostaglandin E2 Is a Product of Induced Prostaglandin-endoperoxide Synthase 2 and Microsomal-type Prostaglandin E Synthase at the Implantation Site of the Hamster

Certain uterine prostaglandins (PGs) are elevated at implantation sites and are needed to trigger the events of blastocyst implantation that include blastocyst-uterine attachment and stromal decidualization with vascular permeability changes. Several decades of investigations showed that treatment with PG synthesis inhibitors, prior to or during the time of implantation, resulted in either complete inhibition or a delay in implantation or reduction in the number of implantation sites with diminished decidual tissue. Consistent with these findings, we observed that whereas a selective PG endoperoxide synthase (Ptgs) 1 inhibitor SC-560 failed to inhibit implantation, a selective Ptgs2 inhibitor SC-236 showed significantly reduced number and size of implantation sites in progesterone-treated ovariectomized pregnant hamsters. It is known that Ptgs2 expression and Ptgs2-derived prostacyclin (PGI2) synthesis at implantation sites are needed for implantation in the mouse (a rodent that needs ovarian estrogen for implantation). However, it is unknown which Ptgs and PG synthases produce which PGs at implantation sites of the hamster (a rodent that does not need ovarian estrogen for implantation). Here we demonstrate that as blastocyst implantation proceeds, a reduction in Ptgs1 expression from uterine luminal epithelial cells and a gradual induction in Ptgs2 expression exclusively in luminal epithelial and adjacent decidual cells occurred at implantation sites of hamsters. Results also reveal that PGE2, but not PGI2, is the major PG at implantation sites where Ptgs2 and microsomal type PGE synthases but not PGI synthases are co-expressed. This elevated uterine PGE2 at implantation sites may serve to initiate or amplify physiological signals required for specific aspects of the implantation process in hamsters.

Effect of oestrous cycle and early pregnancy on uterine production and expression of immune regulatory factors in gilts

This study was undertaken to characterize uterine immune factors involved in the establishment of pregnancy in gilts. Thirty crossbred Yorkshire–Landrace gilts of similar age and weight were observed twice a day for oestrous behaviour with intact boars. On the day of first standing oestrus (Day 0) and 12 h later, 15 gilts were inseminated with pooled semen from Duroc boars of proven fertility. Pregnant gilts were slaughtered either on Days 10, 15 or 25 of gestation ( n=5 per day). The other 15 gilts were not inseminated and were slaughtered on either Days 0, 10 or 15 of the oestrous cycle ( n=5 per day). Immediately after slaughter, endometrial tissue samples from the mesometrial side were removed for gene expression using RNase protection assay and in situ hybridization methodologies. The other uterine horn was flushed with 20 ml of PBS to collect the uterine fluid. In pregnant gilts, endometrial interleukin (IL)-6 mRNA expression was higher on Day 15 than on Days 10 and 25 ( P<0.01 and P<0.1, respectively). On Day 15, IL-6 expression was also significantly higher ( P<0.01) in pregnant gilts than in cyclic gilts. In both pregnant and cyclic gilts, transforming growth factor (TGF)-β2 in uterine fluid was significantly higher ( P<0.0001) on Day 15 than on Day 10. At the gene expression level, TGF-β2 also increased between Days 10 and 15 in both cyclic and pregnant gilts but differences were not significant. On Day 15, concentrations of interferon-γ and prostaglandin E 2 (PGE 2) in uterine fluid were markedly higher ( P<0.001) in pregnant gilts than in cyclic gilts, whereas the total amount of TGF-β2 in uterine fluid and its endometrial expression were approximately 70% higher although this increase was not significant. Finally, tumour-necrosis factor-α and granulocyte-macrophage/colony-stimulating factor mRNA expressions were undetectable in all endometrial samples. In conclusion, production and/or expression of uterine TGF-β2, IL-6 and PGE 2 increased during the embryonic attachment period and are coincidental with embryonic interferon-γ production.

Relationship between endotoxin and prostaglandin (PGE 2 and PGFM) concentrations and ovarian function in dairy cows with puerperal endometritis

Blood concentrations of progesterone, 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM) and endotoxin, and uterine fluid concentrations of prostaglandin E 2 (PGE 2), PGFM and endotoxin were evaluated in 14 dairy cows with puerperal endometritis (mild ( n=6) and heavy ( n=8)). Endotoxin was measured using a quantitative kinetic assay. Cows with heavy endometritis had significantly higher concentrations of plasma PGFM ( P<0.01) and uterine fluid PGE 2 and endotoxin ( P<0.05) than cows with mild endometritis. Concentrations of PGFM in plasma and uterine fluid, of PGFM and PGE 2, and PGE 2 and endotoxin in uterine fluid were positively and significantly ( P<0.05) correlated. The presence of endotoxin in plasma was detected in one out of six mild and in eight out of eight heavy endometritis cows. Peak plasma endotoxin concentrations (0.08–9.14 endotoxin units/ml (EU/ml) were observed between 1 and 12 days postpartum (pp) and thereafter amounts generally remained below 0.1 EU/ml (last day of detection: Day 27 pp). Abnormal ovarian function was observed in six cows (four with prolonged anoestrus and two with long luteal phase after the first postpartum ovulation). Plasma endotoxin concentrations were detected in the anoestric cows. The results suggest that: (i) concentrations of uterine fluid endotoxin and PGE 2 and of plasma PGFM are related to the degree of endometritis; (ii) absorption of endotoxin from the uterus to the bloodstream occurs, mainly in heavy endometritis cows; and (iii) there is a relationship between uterine infection, endotoxin production and resumption of pp ovarian activity.

Regulation by nitric oxide of prostaglandin E synthesis and spontaneous motility in rat uterine tissue

We explored the role of endogenous nitric oxide (NO) in the spontaneous motility of uterine tissue from pseudopregnant (psp) rats and the correlation between this action and the uterotonic prostaglandin (PG) E production. We worked in the early psp (on day 5 of psp), and in late psp (on day 8 and day 9). Treatment with N G-monomethyl- l-arginine l-NMMA (300 μM), a competitive nitric oxide synthase (NOS) inhibitor, did not modify isometric developed tension (IDT) and frequency of contractions (FC) on day 5 of psp; on day 8, tissue pretreated with l-NMMA showed an increase in the IDT and FC compared with controls, while on day 9 of psp, both IDT and FC showed a lower stability after treatment with the inhibitor. These data suggest that NO modulates uterine motility on day 8 (decreasing it) and on day 9 of psp (enhancing it). We also evaluated the total NOS activity and that of its isoforms at the three times mentioned, demonstrating that total NOS activity was higher on day 5 of psp and decreased with psp development. On day 5 of psp, calcium-dependent and calcium-independent NOS each forms around 50% of total NOS activity. On day 8 of psp, the calcium-dependent was the predominant NOS form, while on day 9 of psp, the uterine tissue showed a higher calcium-independent form of the enzyme. In view of the fact that we found an inhibitor effect of the endogenous NO in uterine contractility on day 8 of psp and an inverse action on day 9 of psp (enhancing uterine contractility), we suggest that the NOS calcium-dependent form could be responsible for uterine contractility in psp rats. Finally, we evaluated the relationship between endogenous NO and PGE production. We observed that on days 5 and 8 of psp, the L-NMMA (300 μM) treatment did not affect PGE production, but on day 9 of psp, the preincubation with the NOS inhibitor diminished PGE synthesis, suggesting that at this time endogenous NO can upregulate uterine PGE production. These results confirm that NO can modulate uterine motility by means of PGE production. In summary, we suggest that in uterine tissue from psp rats, the NO system can alternatively decrease or increase uterine contractions, this last effect by enhancing uterine PGE synthesis.

Uterine and ovarian responses to puberty induction and pregnancy in prepubertal gilts.

We evaluated the effect of age on response to puberty induction in gilts. Sequential treatment with a commercial gonadotropin mixture (400 IU PMSG, 200 IU hCG) followed 96 h later with hCG (500 IU) was used to induce follicular growth and ovulation, respectively. In the first experiment, gilts (84, 104, 124, 144, and 164 d old) were used. Peripheral blood was collected on d 0 (before treatment) and on d 2, 3, 4, 8, and 16 after treatment. On d 16, all gilts were hysterectomized, uterine flushings were collected, and uterine weight (UTWT) and length (UTLG) were measured. For treated gilts, UTWT, UTLG, number of corpora lutea (CL), peripheral progesterone (P4) on d 16, and estradiol (E2) on d 4 increased (P < .05) linearly with age. Uterine luminal PGE (P < .05) and PGF (P = .07), expressed per UTWT, responded quadratically with age; gilts treated at 124 d of age or older showed decreased amounts. Overall, the number of CL correlated positively (P < .01) with UTWT and P4 on d 8 and 16. Peripheral P4 on d 4, 8, and 16 (P < .10) and E2 on d 0 and 4 (P < .01) were correlated positively with uterine weight on d 16. Gilts induced to ovulate at 104 and 144 d of age had heavier and longer uteri (P < .01), more P4 on d 8 and 16 (P < .05), and more E2 on d 2 (P < .1) and 4 (P < .05) than controls at the same age. The second experiment evaluated pregnancy success for gilts induced to ovulate at 116 vs 151 d of age. The effects of induction of two consecutive estrous cycles also were evaluated. Two of seven (28.6%) and four of nine (44.4%) gilts first treated when 116 and 151 d old but none of seven gilts treated at 96 and 116 d of age were pregnant 60 d after insemination. Results indicate that induction of a prior cycle did not improve pregnancy rates. However, some gilts in this population maintained pregnancies to 60 d when induced to ovulate and inseminated at 120 d of age.

Effect of mifepristone and antiestrogens on uterine PGF 2α and PGE 2 concentrations in ovariectomized and pregnant rats

Four antiestrogens (anordiol, tamoxifen, RU 39411, ICI 182780) and the antiprogestin, mifepristone (RU 486), were administered to the following three animal models: (1) ovariectomized rats, (2) mated rats treated post-coitally; and (3) pregnant rats treated post-implantation. The antiestrogens were administered alone or in combination with mifepristone at doses effective in preventing and/or terminating pregnancy in rats. The objective of the study was to determine whether these drugs influenced uterine concentrations of prostaglandins (PGF 2α and PGE 2). Antiestrogens administered alone to ovariectomized rats did not effect uterine PGE 2 or PGF 2α concentrations; whereas the combination of anordiol/mifepristone increased uterine PGF 2α concentration, resulting in an increase in the PGF 2α/PGE 2 ratio. Mated rats were treated post-coitally for three consecutive days with anordiol, tamoxifen, estradiol and mifepristone alone and with the combination of anordiol/mifepristone and tamoxifen/mifepristone. An increase in uterine PGF 2α concentrations and in the PGF 2α/PGE 2 ratio occurred only in anordiol/mifepristone treated group. A decrease in uterine PGE 2 concentrations occurred in animals treated with anordiol, tamoxifen and estradiol, resulting in an increase in the PGF 2α/PGE 2 ratio. Anordiol (5.0 mg/kg/day) and mifepristone (4.0 mg/kg/day) alone and the combination of anordiol/mifepristone (2.5/1.0 mg/kg/day) administered to pregnant rats on days 7, 8 and 9 of pregnancy induced an increase in PGF 2α levels without affecting uterine PGE 2 concentration. The changes in uterine PGF 2α concentrations induced by anordiol and the combination of anordiol/mifepristone resulted in an increase in the PGF 2α/PGE 2 ratio. The antiestrogens tested except for ICI 182780 possessed agonist activity when assayed by measuring their capacity to increase the uterine weights in ovariectomized rats. Also, ICI 182789 was the only antiestrogen that did not influence uterine PG concentrations. It can be concluded that ICI 182780 is the only “pure” antiestrogen among those tested. The present results show that antiestrogens and the combination of mifepristone plus anordiol at doses preventing implantation and terminating pregnancy increase uterine PGF 2α and/or decrease PGE 2 concentrations, resulting in an alteration of PGF 2α/PGE 2 ratio. These findings suggest that there exists a critical balance of PGF 2α to PGE 2 concentrations in the uterus required for the normal passage of fertilized ova through the oviduct, initiating implantation of the blastocysts, development of embryos, and maintenance of pregnancy.

Prolactin regulates uterine synthesis of prostaglandins in ovariectomized rats. Effect of estradiol 17-beta

We studied the in vitro effect of prolactin on the synthesis of prostaglandins PGE and PGF 2α in the rat uterus. Uterine tissue was obtained from ovariectomized adult rats with or without estradiol-17 beta treatment. Prolactin (4 IU/ml) enhanced PGE uterine synthesis. At higher concentrations (10–15 IU/ml) prolactin enhanced PGE levels and diminished PGF 2α production by uterine tissue from ovariectomized rats. When ovariectomized rats were injected with estradiol-17 beta, we observed a pattern of PGE and PGF 2α uterine synthesis similar to that of ovariectomized rats. However, the stimulatory action of PRL on PGE synthesis was augmented in the estrogenized animals. These results led us to conclude that: 1)-PRL exerts a luteotrophic action by regulating uterine tissue PGE synthesis, 2-estradiol-17 beta potentiates this action.

Early onset of parturition induced by acute alcohol exposure in C57BL/6J mice: role of uterine PGE and PGF2alpha.

These studies were designed to determine the effect of acute alcohol treatment on gestational length and to probe for a mechanism underlying alcohol-induced early onset of parturition (EOP) in mice. Experiment 1: alcohol increases the incidence of EOP. Pregnant C57BL/6J mice were given alcohol (0, 4, 5 or 6 g kg(-1), i.g.) on Gestational Day (GD) 10, 15, 16, 17 or 18. Deliveries were monitored every 6 h from GD 18. Results indicated that 6 g kg(-1) alcohol treatment on GD 17 or 18 increased the incidence of EOP. Experiment 2: prostaglandins (PGs) play roles in parturition. The purpose of Experiment 2 was to determine whether PGs mediate alcohol-induced EOP in mice. The results indicated that pretreatment on GD 17 with aspirin, a prostaglandin synthesis inhibitor, prevented alcohol-induced EOP. These data suggest that alcohol-induced EOP in mice may be mediated by PGs. Experiment 3: PGs are influenced by alcohol and are triggers of labour. Experiment 3 measured uterine PGs associated with the onset of alcohol-induced EOP in mice. Alcohol increased uterine PGE and PGF2alpha, with PGE levels higher than control before labour, and elevated PGF2alpha levels correlating with labour. Changes in gestational length have important implications for pregnancy outcome, as well as for normal fetal growth and development.

Relationships among sex steroids, oxytocin, and their receptors in the rat uterus during late gestation and at parturition.

Sex steroids and oxytocin (OT) produced within intrauterine tissues have been implicated in the regulation of parturition. The purpose of these studies was 1) to determine the relationships among estradiol (E2), progesterone (P4), OT, and their receptors in uterine tissues during late gestation and parturition in the rat; 2) to observe the effects of the estrogen antagonist tamoxifen (TAM) on these factors; and 3) to evaluate the rat as a potential model for events at human parturition. Concentrations of E2, P4, PGE2, and OT were measured by RIA. E2 receptor (ER) was measured by enzyme immunoassay, and P4 receptor (PR) and OT receptor (OTR) were measured by binding assays. OT messenger RNA (mRNA) was measured by ribonuclease protection assay. Groups (n = 5) of pregnant rats (normal gestation = 22 days) were treated with TAM (200 mg/day) or vehicle and killed on gestation day 19, 21, 21.5, or 22 or after delivery of the first pup. Serum E2 increased throughout late gestation accompanied by an increase in uterine OT mRNA and ER. Serum P4 declined after day 19, and uterine PR did not change significantly. Uterine PGE2 increased progressively, reaching peak levels the evening before delivery. Uterine OTR did not increase until the morning of delivery, and uterine OT peptide concentrations increased only during parturition. Parturition was significantly delayed by 24 h in the TAM-treated group. TAM inhibited the increase in serum E2, uterine ER, and OT mRNA and peptide, but had no effect on serum P4 or uterine PR levels. With TAM, the responses of uterine OTR and PGE2 were significantly delayed, but still underwent a significant increase before the delayed parturition. These results support the hypothesis that E2 stimulates the synthesis of ER, OT, and OTR within the rat uterus and is essential for normal parturition. P4 withdrawal may be more important to the increases in OTR and PGE2, but these are delayed in the absence of estrogen. These data also suggest that the rat may be a relevant model for human parturition.

Interaction between uterine PGE and PGF 2α production and the nitridergic system during embryonic implantation in the rat

Embryonic implantation is a complex process in which both maternal andembryonic signals are involved. In the present study, we evaluated changes in uterine prostaglandins production and nitric oxide synthase (NOS) activity during the course of early pregnancy and their interaction during implantation in rats. Uterine phospholipase A 2 (PLA 2) activity is increased on days 5 (day of ovoimplantation) and 6, compared to preimplantation days (3 and 4). This enhanced activity might be responsible for the observed increase in uterine PGE and PGF 2α production observed on day 5 of pregnancy, which induces endometrial vascular permeability and decidualization. When embryo access to the uterus is impaired, the increase of PG production is suppressed. During postimplantation, PGE levels return to preimplantation values, while PGF 2α decreased with respect to preimplantation values. Uterine NOS activity is also increased on day 4 and reaches a maximum on day 5, with a profile similar to PGE and PGF 2α Dexamethasone administered in vivo decreased uterine NOS activity on day 4 of pregnancy but not on day 5, suggesting the presence of at least two types of NOS enzymes in the early days of pregnancy. A competitive inhibitor of NOS, L-NAME (600 and 1000 μM) induced a decrease in PGE and PGF 2α production in uterine tissue on day 5 of pregnancy. These results suggest the existence of a physiologically relevant nitridergic system which modulates prostaglandin production in the rat uterus during embryonic implantation.

Prostaglandin E 2 levels in uterine tissues and its relationship with uterine and luteal progesterone during the estrous cycle in dairy cows

Endometrial tissue homogenates obtained at luteal and follicular stages of the estrous cycle were determined for prostaglandin E 2 and progesterone contents by EIA and RIA, respectively. In Experiment 1, the concentrations and changes of PGE 2 in uterine tissues collected by biopsy before slaughfter and subsequent samples collected at 30, 60 and 90 min after slaughter were measured. No significant differences were observed in the concentration of PGE 2 preslaughter or at 30 and 60 min post slaughter. However, there was a significant decrease (P<0.01) in PGE 2 concentration 90 min post slaughter. In Experiment 2, the concentrations of PGE 2 in the ipsilateral and contralateral horns in relation to corpus luteum function were compared. A significant (P<0.05) interaction was found between stages of estrous cycle (luteal vs follicular) based on CL progesterone content, and type of uterine horn (ipsilateral vs contralateral) on uterine PGE 2 levels. The PGE 2 concentration was significantly higher (P<0.01) at luteal phase than at follicular phase. During the luteal phase PGE 2 concentrations in tissues of the uterine horn ipsilateral to the corpus luteum was significantly higher (P<0.01) than the contralateral horn. The PGE 2 concentration was low and did not differ significantly between horns during follicular phase. A parallel increase (luteal: high) and decrease (follicular: low) in PGE 2 and progesterone concentrations were observed. Correlations were observed for CL progesterone and uterine PGE 2 concentrations as well as for PGE 2 and progesterone concentrations in uterine tissues (r=0.70 and r=0.60, respectively). The results show that the increase in PGE 2 concentrations in uterine tissues coincides with the high uterine progesterone concentrations during luteal phase.

The effect of caffeine on prostaglandin output from the guinea-pig uterus.

1. Caffeine increased the outputs of prostaglandin F2 alpha (PGF2 alpha), PGE2 and 6-keto-PGF1 alpha from the guinea-pig uterus on days 7 and 15 of the oestrous cycle. The effect on PGE2 output depended on the age of the animals and was absent in younger guinea-pigs (< 4 months). Theophylline also stimulated the outputs of PGF2 alpha and 6-keto-PGF1 alpha, but not the output of PGE2, from the day 7 guinea-pig uterus. 2. The stimulatory effects of caffeine on the outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha from the guinea-pig uterus were not prevented by lack of extracellular calcium, ryanodine or ruthenium red (both inhibitors of calcium release via the ryanodine receptor), although the increase in PGF2 alpha output tended to be slower when extracellular calcium was absent. Also, ryanodine flattened and broadened the peak of increased PGF2 alpha release. 3. The calmodulin antagonists, W-7 and trifluoperazine, had no inhibitory effect on the caffeine-stimulated increases in uterine prostaglandin output. In fact, W-7 (but not trifluoperazine) greatly potentiated the action of caffeine on uterine PGF2 alpha output, but had little or no potentiating effect on the action of caffeine on uterine PGE2 and 6-keto-PGF1 alpha outputs. 4. TMB-8, an intracellular calcium antagonist, inhibited the increase in PGF2 alpha output produced by caffeine without preventing the increases in outputs of PGE2 and 6-keto-PGF1 alpha. 5. These studies suggest that caffeine stimulates uterine PGF2 alpha synthesis and release by a mechanism dependent upon intracellular calcium, but this mechanism is not mediated by activation of any of the three well-characterized ryanodine receptors or by calmodulin. Furthermore, the increases in the synthesis and release of PGE2 and 6-keto-PGFI alpha. in the guinea-pig uterus induced by caffeine appear to involve mechanism(s) different from that which stimulates PGF2 alpha production.

The direct influence of the embryo on uterine PGF2 and PGE2 production in sheep

In unilateral pregnant ewes, obtained by surgically transecting one uterine horn to isolate it from the rest of the pregnant uterus, the isolated horn develops endometrial oxytocin receptors by day 16 despite being in a hormonal environment equivalent of that of a pregnant ewe. This study examines uterine prostaglandin production in these animals. On day 16 of pregnancy, ewes were anaesthetized and a uterine vein draining each horn and the jugular vein cannulated. Venous blood samples were taken at 10 min intervals for 1 h before and 1 h after an i.v. injection of oxytocin (1 microgram). Uterine vein samples were assayed for PGF2 alpha and PGE2 and jugular blood samples assayed for 13,14-dihydro,15-keto-PGF2 alpha. All ewes showed high plasma concentrations of 13,14-dihydro,15-keto-PGF2 alpha after the oxytocin injection. PGF2 alpha increased in the uterine vein draining the nonpregnant transected horn of a unilaterally pregnant ewe following oxytocin treatment, whereas there was no increase in concentration in plasma draining the pregnant horn. Basal plasma PGF2 alpha concentrations from the uterine vein draining the pregnant horn were significantly higher than concentrations obtained from the uterine vein of the transected horn while PGE2 concentrations did not vary between the two horns. After oxytocin injection, there was a significant increase in plasma PGE2 concentration in venous blood collected from both sides.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin E 2 production by uterine stromal cell line U III: Regulation by estradiol and evidence of an ethanol action

We have recently established a uterine stromal cell line (U III). The purpose of the present study was to determine whether these cells have retained the ability to produce and release prostaglandins after several passages and whether this production was regulated. U III cells, grown in basal conditions, released a very low amount (40.6 ± 2.9 pg/24h/10 6 cells) of prostaglandin E 2 (PGE 2) though cellular content was more elevated (192 ± 23 pg/10 6 cells). Ethanol increased the cellular content but decreased the release of PGE 2, whereas estradiol 17 β (E 2) increased it in a dose-dependent manner, but had no effect on the cellular content. The PGE 2 release by cells grown in medium containing 10 μM arachidonate (AA) reached 1.39 ± 0.05 ng/24h/10 6 cells, and was further increased to 2.1 ± 0.1 ng/24 h/10 6 cells by the addition of ethanol. Under the latter condition, E 2 was ineffective. This study also showed that U III cells expressed an immunoreactive pancreatic type 14 kD PLA 2. A substantial increased 14 kD PLA 2 expression was observed in ethanol-treated cells, suggesting that ethanol-effect on prostaglandin production might be partly mediated by PLA 2 increase. Medium supplementation with arachidonate also resulted in a significant increase of intracellular 14 kD PLA 2 expression. The present results showed that uterine stromal U III cells have retained the enzymatic machinery to produce PGE 2. Moreover these data demonstrate that ethanol and E 2 affect differently uterine PGE 2 production.

Luteal maintenance during early pregnancy in the pig: Role for prostaglandin E 2

We previously demonstrated that prostaglandin E 2 (PGE) directly inhibits prostaglandin F 2α (PGF)-induced regression of individual pig corpora lutea (CL) in a dose dependent manner. The present experiments were conducted to 1) characterize and compare uterine secretion of PGE and PGF during the estrous cycle and early pregnancy and 2) evaluate the local effect of the conceptus on uterine prostaglandin secretion and associated CL function in unilaterally pregnant pigs. In Experiment 1, utero-ovarian venous blood samples were collected from two nonpregnant and two pregnant gilts at 3-h intervals from day 10 through 16 (first day of estrus or mating = day 0) for quantitation of uterine PGE and PGF secretion. In Experiment 2, gilts (n=4) were made unilaterally pregnant on day 2, and utero-ovarian venous catheters were placed bilaterally to determine if differences in PGE and/or PGF secretion might account for the known luteotrophic/antiluteolytic effect of the gravid uterine horn on the CL of the ipsilateral ovary. During the estrous cycle (Experiment 1), pulsatile secretion of PGF increased markedly on day 13 and continued to increase through day 16. PGE secretion also increased from day 13 to 16 of the estrous cycle; however, concentrations of PGE remained at least 3-fold lower than those of PGF. In contrast to changes in non-mated gilts, prostaglandin secretion in mated gilts peaked earlier (day 11–12), with PGE predominating. Thereafter, both PGE and PGF secretion declined to basal levels where they remained through day 16 of pregnancy. During unilateral pregnancy (Experiment 2), PGF concentration in nongravid and gravid horns was similar ( P > 0.8). In contrast, PGE concentrations were greater ( P < 0.06) in utero-ovarian venous blood draining the gravid uterine horn. This increase in PGE was associated with enhanced CL function on the ipsilateral ovary as evidenced by an elevated progesterone content and concentration as well as increased CL weights. These data are consistent with a role for conceptus-associated increases in uterine PGE secretion in the local stimulation of luteal function during early pregnancy in the pig.