Estradiol enhances prostaglandin synthase activity in epithelial but not in stromal cells of human endometrium

Exogenous estradiol (E2) has been shown to elevate PGF2 alpha output by explants of human secretory endometrium and in monolayer cultures of glandular epithelial, but not of stromal cells isolated from endometrium. In this study, PGF2 alpha output was measured in each of these cultures in the presence of E2 and the calcium ionophore A23187, added singly or in combination. The ionophore, known to liberate arachidonic acid (AA) by stimulating phospholipase activity, produced a calcium-dependent increase in PGF2 alpha output in the cultures of epithelial cells, whereas greater than additive effects were obtained with mixtures of E2 and A23187. In contrast, PGF2 alpha levels were not elevated by A23187 in the stromal cell cultures even in medium supplemented with CaCl2 or when E2 was added. A calcium-dependent increase in PGF2 alpha output was also observed in fragments of secretory endometrium incubated with A23187. Effects on PGF2 alpha output by endometrial fragments incubated with E2 and A23187 were essentially additive and intermediate between those of the two component cells types. Arachidonic acid produced similar increases in PGF2 alpha output in the epithelial and stromal cell cultures but only in the epithelial cell cultures was there greater utilization of AA in the presence of E2. When mixtures of E2 and AA were added to the cultures of epithelial cells the increase in PGF2 alpha output was 2.5-fold greater than the sum of the increases elicited by E2 or AA alone. In contrast, no enhancement of the AA effect by E2 was observed in the stromal cell cultures. Extrapolation of these results from cell cultures to intact tissue suggests that the epithelium and not the stroma is the primary target for the effects of E2 on PGF2 alpha output by secretory endometrium. The synergistic actions of E2 and either AA, the obligatory precursor of PGF2 alpha, or A23187, an enhancer of AA release from phospholipid stores, point to a stimulatory effect of E2 on prostaglandin synthase activity.     

Activity of phospholipase C and release of prostaglandin F2 alpha by endometrial tissue from ovariectomized ewes receiving progesterone and estradiol

Progesterone and estradiol interact to regulate secretion of prostaglandin (PG) F2 alpha from the ovine endometrium in response to oxytocin. Two experiments were conducted to determine if these effects were due to changes in activity of phospholipase C or in the second messenger responsive pathways that regulate production of PGF2 alpha. In both experiments, ovariectomized ewes were assigned to one of four treatment groups (control, estradiol, progesterone, progesterone and estradiol). Steroids were administered, in vivo, to mimic the changes that occur during the estrous cycle. On Day 16 of steroid treatment, endometrial tissue was collected and incubated, in vitro, to measure activity of phospholipase C and release of PGF2 alpha. Treatment with progesterone, in vivo, enhanced basal and oxytocin-induced activity of phospholipase C and release of PGF2 alpha, in vitro. Estradiol suppressed oxytocin-induced activity of phospholipase C, both in the presence and absence of progesterone. In contrast to its effects on phospholipase C, estradiol inhibited basal and oxytocin-induced release of PGF2 alpha when administered alone, but not when administered with progesterone. Steroids had similar effects on the release of PGF2 alpha induced by phorbol 12-myristate 13-acetate and A23187. It was concluded that progesterone and estradiol regulate endometrial release of PGF2 alpha by affecting both the activity of phospholipase C and its associated second messenger responsive pathways that may regulate production of PGF2 alpha.     

Prostaglandin F2 alpha output by human endometrium under superfusion and organ culture conditions

Specimens of proliferative and secretory human endometrium were incubated under organ culture or superfusion conditions and the levels of PGF2 alpha in the medium were measured by radioimmunoassay. Basal rates of PGF2 alpha output during short-term superfusions and long-term (1-2 day) batch incubations, performed on the same tissue specimens, were similar. Basal output of PGF2 alpha by proliferative endometrium (230-280 ng/mg protein X d) was significantly higher than that of secretory tissue under both experimental conditions. Estradiol (10(-8) M) increased PGF2 alpha output significantly (4-fold) only in secretory endometrium under organ culture conditions; Progesterone (10(-7) M) decreased it significantly (to 1/2-1/4 of the basal level) in both types of endometria during long-term incubations and in proliferative endometrium during superfusion. Glands isolated from proliferative and secretory endometrium produced PGF2 alpha during superfusion at a rate comparable to that of endometrial tissue under similar conditions. PGF2 alpha output by glands isolated from secretory endometrium increased significantly (3-fold) when estradiol was added to the superfusion medium.     

Expression of tenascin-C in stromal cells of the murine uterus during early pregnancy: induction by interleukin-1 alpha, prostaglandin E(2), and prostaglandin F(2 alpha)

Tenascin-C (TN-C), an extracellular matrix glycoprotein, is known to be expressed in uterine stroma in the peri-implantation period. Examination of the spatiotemporal pattern during early pregnancy using immunohistochemistry and in situ hybridization revealed TN-C expression in the stroma beneath the luminal epithelia of the murine endometrium on Days 0 and 1 of pregnancy, subsequent disappearance, and reappearance on Day 4. After decidualization, tissue around the deciduoma was positive. In situ hybridization demonstrated TN-C production by the stromal cells adjacent to the epithelia. To investigate the regulation of TN-C expression in vitro, murine uterine stromal and epithelial cells were isolated and cultured. Addition of interleukin-1 alpha (IL-1 alpha) and prostaglandin E(2) (PGE(2)) and F(2 alpha) (PGF(2 alpha)) induced TN-C expression in the stromal cells at both protein and mRNA levels, while the sex steroid hormones, progesterone and ss-estradiol, exerted little effect. Immunohistochemistry using anti-IL-1 alpha antibody showed epithelial cells to be positive on Days 2-4 of pregnancy, and addition of progesterone but not ss-estradiol enhanced IL-1 alpha expression in epithelial cells in vitro. In a culture insert system, TN-C expression by stromal cells cocultured with epithelial cells was induced by addition of progesterone alone that was blocked by additions of anti-IL-1 alpha antibody. Collectively, these findings indicate that TN-C expression in the preimplantation period is under the control of progesterone, but not directly, possibly by the paracrine and autocrine intervention of IL-1 alpha secreted by epithelial cells and PGE(2) and PGF(2 alpha) secreted by stromal cells.     

The effect of progesterone and human interferon alpha-2 on the release of PGF2 alpha and PGE from epithelial cells of human proliferative endometrium.

Progesterone and interferon-like trophoblastic proteins modulate prostaglandin (PG) synthesis from endometrium in early ovine and bovine pregnancy. Enriched epithelial cells were prepared from human endometrium removed in the proliferative phase of menstrual cycle (n = 8). Progesterone at a concentration of 1 microM suppressed PGE release from the cells during the first 24 hours in culture. After 48 hours in culture progesterone at a dose of 100 nM and 1 microM suppressed both the release of PGF2 alpha and PGE from the cells and this suppression was maintained for a further two days. Addition of exogenous 30 microM arachidonic acid (AA) abolished this effect of progesterone on both PGF2 alpha and PGE release. Interferon alpha-2 did not suppress the basal release of PGF2 alpha nor PGE. In the presence of progesterone, interferon alpha-2 attenuated the progesterone mediated suppression of PGF2 alpha but not PGE release from endometrial cells. These findings suggest that progesterone suppresses the basal release of PGs from human endometrium, but unlike the sheep, interferon alpha-2 does not exert this action on human endometrium.     

In vitro evaluation of estrogenic, estrogen antagonistic and progestagenic effects of a steroidal drug (Org OD-14) and its metabolites on human endometrium

The human endometrial model for in vitro evaluation of estrogenic, estrogen antagonistic, and progestagenic effects of endogenous steroids, natural products or synthetic drugs was applied to the study of Org OD-14, an analog of norethynodrel developed by Organon International, Oss, The Netherlands, and some of its metabolites. Estrogen antagonistic actions of Org OD-14 and its 4-ene isomer were evident from their ability to suppress the enhancement of PGF2 alpha output elicited by estradiol on fragments of secretory endometrium and to decrease the rate of output of the prostaglandin by proliferative tissue, already stimulated by endogenous estrogens. These inhibitory effects were similar to those obtained with progesterone and do not appear to involve competition for the estrogen receptor since the antiestrogen 4-hydroxyamoxifen was not active in parallel incubations of proliferative endometrium. The progestagenic effects of Org OD-14 and its 4-ene isomer were also evident from their capability to enhance estradiol 17 beta-dehydrogenase activity and glycogen accumulation in specimens of proliferative endometrium. Estrogenic effects of the 3 alpha- and 3 beta-hydroxy metabolites of Org OD-14 were demonstrated by their stimulatory actions on PGF2 alpha output during incubations of secretory endometrium. The estrogenic and progestagenic actions of these compounds are in general agreement with their relative affinity for binding to the estradiol and progesterone receptors, although their actions may be influenced by intracellular metabolism in the endometrial tissue. For instance, the similarity in progestagenic activity of Org OD-14 and the 4-ene isomer, contrasting with their different affinities for the progesterone receptor, may result from in situ isomerization of Org OD-14 to the 4-ene metabolite.     

Steroid hormone modulation of prostaglandin secretion in the ruminant endometrium during the estrous cycle

Prostaglandins, produced from membrane phospholipids by the action of phospholipase A2, cyclooxygenase, and specific prostaglandin synthases, are important regulators of ovulation, luteolysis, implantation, and parturition in reproductive tissues. Destruction of the corpus luteum at the end of the estrous cycle in nonpregnant animals is brought about by the pulsatile secretion of prostaglandin F(2alpha) (PGF(2alpha)) from the endometrium. It has been known for many years that progesterone, estradiol, and oxytocin are the hormones responsible for luteolysis. To achieve luteolysis, two independent processes have to be coordinated; the first is an increase in the prostaglandin synthetic capability of the endometrium and the second is an increase in oxytocin receptor number. Although progesterone and estradiol can modulate the expression of the enzymes involved in prostaglandin synthesis, the primary reason for the initiation of luteolysis is the increase in oxytocin receptor on the endometrial epithelial cells. Results of many in vivo studies have shown that progesterone and estradiol are required for luteolysis, but it is still not fully understood exactly how these steroid hormones act. The purpose of this article is to review the recent data related to how progesterone and estradiol could regulate (initiate and then turn off) the uterine pulsatile secretion of PGF(2alpha) observed at luteolysis.     

Effects of oestradiol, progesterone, hydrocortisone and oxytocin on prostaglandin output from the guinea-pig endometrium maintained in tissue culture

The effects of oestradiol, oxytocin, progesterone and hydrocortisone in vitro on prostaglandin (PG) output from guinea-pig endometrium, removed on days 7 and 15 of the oestrous cycle and maintained in tissue culture for 3 days, have been investigated. Oestradiol (3.7 to 3700 nM) and oxytocin (2 to 200 pM) did not stimulate endometrial PGF2 alpha output, thus not confirming the findings of a previous report (Leaver & Seawright, 1982), nor did they stimulate the outputs of PGE2 and 6-keto-PGF1 alpha. In fact, oestradiol (3700 nM) inhibited the outputs of PGF2 alpha, PGE2 and, to a lesser extent, 6-keto-PGF1 alpha. Progesterone (3.2 to 3200 nM) inhibited the outputs of PGF2 alpha and PGE2; hydrocortisone (2.8 to 2800 nM) had no effect on endometrial PG output. These findings indicate that the inhibitory effect of progesterone on endometrial PG synthesis and release in the guinea-pig is not due to progesterone having a glucocorticoid-like action. Furthermore, progesterone had no effect on 6-keto-PGF1 alpha output, suggesting that the mechanisms controlling endometrial PGI2 synthesis (as reflected by measuring 6-keto-PGF1 alpha) are different from those controlling endometrial PGF2 alpha and PGE2 synthesis.     

Oxytocin-stimulated production of prostaglandin F2alpha by isolated endometrium of rabbit: modulation by ovarian steroids

To test the hypothesis that ovarian steroid hormones modulate oxytocin-induced release of prostaglandin F2alpha (PGF2alpha) from uterine endometrium, 2 ovariectomized rabbits were pretreated with progesterone (5 mg/day for 10 days), 2 with estradiol-17 beta (25 microgram/day for 10 days), 2 with both steroids, and one with sesame oil only. On the last day of treatment, endometrial fragments were excised and incubated in vitro with or without oxytocin (100 muU/ml). Although endometrium from rabbits pretreated with combined steroids released more PGF2alpha immediately after excision than did tissue from animals pretreated with either steroid by itself, endometrium from animals pretreated with estradiol-17 beta alone released the most PGF2alpha during sustained incubation in vitro. Moreover, only this tissue exhibited significant oxytocin-dependent release of PGF2alpha. At the dosages used, progesterone completely antagonized both of these effects of estradiol-17 beta. The results support the hypothesis that ovarian steroid hormones regulate oxytocin-dependent release of PGF2alpha from endometrial cells. A posible mechanism of action is suggested.     

Progesterone and estradiol secretion by porcine luteal cells is influenced by individual and combined treatment with prostaglandins E2 and F2alpha throughout the estrus cycle.

The present experiments were conducted to test whether the ratio of PGE2:PGF2alpha affects steroid secretion by porcine luteal cells. We examined the effect of separate and combined treatment with PGE2 and PGF2alpha on progesterone and estradiol secretion. Luteal cells were collected at three different stages of the luteal phase (1-3 days after ovulation; 10-12 days after ovulation and 14-16 days after ovulation). PGE2 alone in a dose dependent manner increased progesterone production by cells collected from mature corpora lutea. On the other hand, PGF2alpha in a dose dependent manner decreased progesterone secretion by cells of the same origin. Progesterone secretion by cells isolated from mature and regressing corpora lutea and treated with both prostaglandins increased in comparison to PGF2alpha-treated cultures. However, in cells collected from regressing corpora lutea PGE2 and PGF2alpha in a ratio of 2:1 and 4:1 increased estradiol production when compared to control and both ratios increased estradiol secretion in comparison to PGF2alpha-treated cells. These data 1) confirm the luteotropic effect of PGE2 and the luteolytic effect of PGF2alpha; 2) demonstrate that when the ratio of PGE2 to PGF2alpha changed from 1:1 to 2:1 or 4:1 cells were protected against the inhibitory effects of PGF2alpha on progesterone secretion by cells collected during the mid- and late luteal phase; and 3) suggest that elevated estradiol production by luteal cells, isolated during late luteal phase, under the influence of increased doses of PGE2 may serve as an additional source of estradiol to blastocysts, during early pregnancy in the pig.     

Differential effects of progesterone treatment on the oxytocin-induced prostaglandin F2 alpha response and the levels of endometrial oxytocin receptors in ovariectomized ewes.

The oxytocin-induced uterine prostaglandin (PG) F2 alpha response and the levels of endometrial oxytocin receptors were measured in ovariectomized ewes after they had been given steroid pretreatment (SP) with progesterone and estrogen to induce estrus (day of expected estrus = Day 0) and had subsequently been treated with progesterone over Days 1-12 and/or PGF2 alpha over Days 10-12 postestrus. The uterine PGF2 alpha response was measured after an i.v. injection of 10 IU oxytocin on Days 13 and 14, using the PGF2 alpha metabolite, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), as an indicator for PGF2 alpha release. The levels of oxytocin receptors in the endometrium were measured on Day 14. During the treatment with progesterone, the peripheral progesterone concentrations were elevated and remained above 1.8 ng/ml until the morning of Day 14. The PGFM responses to oxytocin in untreated controls and SP controls were low on both Days 13 and 14 whereas the levels of endometrial oxytocin receptors in the same ewes were high. Treatment with progesterone either alone or in combination with PGF2 alpha significantly (p less than 0.04) increased the PGFM response on Day 14 and reduced the levels of endometrial oxytocin receptors; treatment with PGF2 alpha alone had no effect. It is concluded that progesterone promotes the PGFM response to oxytocin while simultaneously suppressing the levels of endometrial oxytocin receptors. PGF2 alpha treatment had no effect on either the uterine secretory response to oxytocin or the levels of oxytocin receptors in the endometrium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Platelet-activating factor in human luteal phase endometrium

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is one of the most potent mediators of vascular permeability. PAF levels change in the rabbit endometrium just prior to implantation, which suggests that PAF may be a key substance transducing preimplantation embryonic signals. To study whether PAF was present in the human endometrium, and if so, to determine the cellular origin and hormonal regulation of endometrial PAF, specimens were obtained from 14 women (aged 23-42 yr) undergoing elective hysterectomy during the luteal phase of the cycle (plasma progesterone levels greater than 2 ng/ml). No specimens were taken from women with malignant uterine pathology. Stromal cells and epithelial glandular cells were separated by collagenase and DNAse digestion, and then cultured to confluence in vitro in medium 199. Radioimmunoassays of prostaglandin F (PGF) and prolactin in the culture media were used to confirm cell type and viability. PGF release into the culture medium from stromal cells was low (control 1.52 +/- 0.20 ng/ml), and unchanged by hormone treatment. In contrast, release of PGF from unstimulated glandular cells was 6.05 +/- 0.52 ng/ml, and was significantly increased (p less than 0.05) by estradiol or progesterone plus estradiol, to 12.17 +/- 1.67, and 8.60 +/- 0.81, respectively. Progesterone alone was without effect. Prolactin was secreted by stromal cell cultures, increasing steadily from 24 to 120 h. The levels in the medium were increased by progesterone. PAF activity was assessed by rabbit platelet aggregation and serotonin-release bioassays after lipid extraction and separation by thin-layer chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of hydrocortisone, oestradiol and progesterone on A23187-stimulated prostaglandin output from the guinea-pig uterus superfused in vitro

Hydrocortisone (10 micrograms/ml) had no effect on the basal outputs and A23187-stimulated outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha from the Day 15 guinea-pig uterus superfused in vitro. These findings indicate that the high output of PGF2 alpha from the guinea-pig uterus during the last one-third of the oestrous cycle is not modulated by the adrenal glucocorticoid hormones. Progesterone (10 micrograms/ml) had no effect on the A23187-induced increases in PG output from the Day 15 guinea-pig uterus. However, oestradiol (10 micrograms/ml but not 1 microgram/ml) significantly reduced the increases in outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha induced by A23187 from the Day 15 guinea-pig uterus, without affecting basal PG outputs. The increase in uterine tone induced by A23187 in the Day 15 guinea-pig uterus was reduced by 20-50% by oestradiol (10 micrograms/ml). The addition of oestradiol (10 micrograms/ml) and progesterone together (10 micrograms/ml) produced the same effects on the Day 15 guinea-pig uterus as oestradiol alone. Oestradiol (10 micrograms/ml) also reduced the A23187-induced increases in PG output from the Day 7 guinea-pig uterus, but did not reduce the increase in uterine tone. Oestradiol (10 micrograms/ml) reduced the increases in outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha induced by exogenous arachidonic acid from the Day 7 and Day 15 guinea-pig uterus. Previous studies have shown that oestradiol is not a cyclo-oxygenase inhibitor. The present findings suggest that oestradiol, at a relatively high concentration, may interfere with the access of arachidonic acid to the cyclo-oxygenase enzyme. This action of oestradiol may explain its anti-luteolytic action when administered to guinea-pigs in large doses after Day 9 of the cycle.     

The effect of cortisol on the synthesis of prostaglandins (PGF2 alpha, PGE2) by human endometrial fibroblasts in vitro with and without addition of estradiol-17 beta or progesterone

Cortisol is known as a potent inhibitor of phospholipase A2 activity in several tissues. In fibroblast monolayer cell cultures from proliferative human endometrium cortisol alone does not affect the basal PGF2 alpha or PGE2 synthesis. After stimulation of PGF2 alpha production by 10(-7) mol/l estradiol-17 beta increasing concentrations of cortisol up to 10(-5) mol/l dosedependently reduce the PGF2 alpha production. Also the progesterone (10(-4) mol/l) stimulated increase of PGF2 alpha and PGE2 synthesis is inhibited by cortisol (10(-7) mol/l).     

Is the inhibitory effect of progesterone on endometrial prostaglandin F2 alpha production due to an inhibition of protein synthesis?

Progesterone and a high concentration of oestradiol (i) reduced the outputs of prostaglandin (PG) F2 alpha and, to a lesser extent, PGE2 from Day-7 and Day-15 guinea-pig endometrium in culture, but had little or no effect on the output of 6-keto-PGF1 alpha, (ii) prevented the increase in PGH synthase concentrations which normally occur in Day-7 and Day-15 guinea-pig endometrium during culture, and (iii) reduced the synthesis of secreted proteins by Day-15 guinea-pig endometrium in culture. These findings suggest that the inhibitory effect of progesterone and of high concentrations of oestradiol on endometrium PGF2 alpha synthesis is due to an inhibition of the syntheses of proteins involved in PGF2 alpha production.     

Histamine alters prostaglandin output from diestrous rat uteri. Involvement of H2-receptors and 9-keto-reductase

The effects of exogenous histamine (H) on prostaglandin (PG) generation and release in uteri isolated from diestrous rats and the influences of H2-receptors blockers (cimetidine and metiamide) on the output of uterine PGs, were explored. Moreover, the action of H on the uterine 9-keto-reductase, was also studied. Histamine (10(-4) M) failed to alter the basal output of PGE1 but reduced significantly the generation and release of PGE2 and augmented the output of PGF2 alpha. On the other hand, cimetidine (10(-5) M) enhanced the basal release of PGE2 but had no action on the outputs of PGs E1 or F2 alpha. The enhancing effect of H on the production and release of PGF2 alpha was abolished in the presence of cimetidine. Also, the antagonist reversed the influence of H on the output of PGE2. Metiamide, another H2-receptor antagonist, did not alter the basal control generation and release of uterine PGs, but antagonized the augmenting influence of H on PGF2 alpha uterine output, as much as cimetidine did, and prevented the depressive action of H on the release of PGE2 from uteri. Histamine (10(-4) M) significantly stimulated uterine formation of cyclic-adenosine monophosphate, an action which was antagonized by the presence of cimetidine (10(-5) M), a blocker of H2 receptors. Also, histamine (10(-5) M) and dibutyrylcyclic-adenosine monophosphate (DB-cAMP) at 10(-3) M, enhanced significantly the formation 3H-PGF2 alpha from 3H-PGE2. Results presented herein demonstrate that H is able to diminish the generation of PGE2 in uteri from rats at diestrus augmenting the synthesis of PGF2 alpha, apparently via the activation of H2-receptors, enhancing adenylate-cyclase. These effects appear to increase uterine 9-keto-reductase activity which transforms PGE2 into PGF2 alpha. Relationships between the foregoing results and those evoked by estradiol, are also discussed.     

The effects of Arcanobacterium pyogenes on endometrial function in vitro, and on uterine and ovarian function in vivo

Uterine bacterial infection after parturition causes endometritis, perturbs ovarian function and leads to infertility in cattle. Although endometritis is caused by mixed infections, endometrial pathology is associated with the presence of Arcanobacterium pyogenes. The aims of the present study were to determine the effects of A. pyogenes on endometrial function in vitro, and on uterine and ovarian function in vivo. Heat-killed A. pyogenes did not affect the production of prostaglandin F2alpha (PGF) or prostaglandin E(2) (PGE) from endometrial explants, or purified populations of endometrial epithelial or stromal cells. However, the explants produced more PGF and PGE than controls when treated with a bacteria-free filtrate (BFF) cultured from A. pyogenes. Similarly, BFF stimulated PGF and PGE production by epithelial and stromal cells, respectively. So, BFF or control PBS was infused into the uterus of heifers (n=7 per group) for 8 days, starting the day after estrus. Emergence of the follicle wave, dominant follicle or corpus luteum diameter, and peripheral plasma FSH, LH, estradiol, progesterone, PGFM, or acute phase protein concentrations were unaffected by the BFF infusion. In the live animal it is likely that the intact uterine mucosa limits the exposure of the endometrial cells to the exotoxin of A. pyogenes, whereas the cells are readily exposed to the toxin in vitro.     

Effects of tumor necrosis factor-alpha on secretion of prostaglandins E2 and F2alpha in bovine endometrium throughout the estrous cycle

To determine the physiological significance of tumor necrosis factor-alpha (TNFalpha) in the regulation of endometrial prostaglandin (PG) release in cattle, we investigated the effects of TNFalpha on the secretion of PGE2 and PGF2alpha by bovine endometrium during the estrous cycle. Bovine uteri were classified into six stages (estrus: Day 0, early luteal 1: Days 2 to 3, early luteal 11: Days 5 to 6, mid-luteal: Days 8 to 12, late luteal: Days 15 to 17 and follicular: Days 19 to 21). After 1 h of pre-incubation, endometrial tissues (20 to 30 mg) were exposed to 0 or 0.6 nM TNFalpha for 4 h. The PGE2 concentrations in the medium were higher in the luteal stages than in the follicular stage and in estrus. In contrast, PGF2alpha concentrations were higher in the follicular stage and in estrus than in the luteal stages. The ratio of the basal concentrations of PGE2 and PGF2alpha (PGE2/PGF2alpha ratio) was higher in the luteal stages than in the follicular stage and in estrus. Although TNFalpha stimulated both PGE2 and PGF2alpha secretion during the entire period of the estrous cycle, the level of stimulation of TNFalpha on PGE2 output by the bovine endometrium does not show the same cyclical changes as that shown on PGF2alpha output. The stimulation of TNFalpha resulted in a decrease in the PGE2/PGF2alpha ratio only in the late luteal stage. Furthermore, TNFalpha stimulated PGE2 secretion in stromal, but not epithelial cells. The overall results suggest that TNFalpha is a potent regulator of endometrial PGE2 secretion as well as PGF2alpha secretion during the entire period of estrous cycle, and that TNFalpha plays different roles in the regulation of secretory function of bovine endometrium at different phases of the estrous cycle.     

Uterine production of prostaglandins F2 alpha and 6-keto-F1 alpha by ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn.

Ovariectomized early pregnant rats given continuous steroid replacement therapy have been treated with antiprogesterone steroid, ZK98299 or RU38486. At 24 h following treatment, uterine explants in culture were found to produce significantly greater amounts of PGF2 alpha, but not of 6-keto-PGF1 alpha, when compared to controls. ZK98299 and RU38486 gave almost identical levels of uterine PG production. The 6-keto-PGF1 alpha/PGF2 alpha production ratio for uteri of treated rats was decreased by 45% relative to controls. Similar changes in uterine PGF2 alpha production and 6-keto-PGF1 alpha/PGF2 alpha ratio have been shown for ovariectomized early pregnant rats in which progesterone has been withdrawn when compared to control animals. It has been suggested that inhibiting or withdrawing progesterone in rat uteri exposed to estradiol and progesterone may lead to a stimulation of endoperoxide F-reductase and/or E2 9-ketoreductase activities. The presence of luminal fluid in the uteri was observed for animals treated with antiprogesterone steroid or in which progesterone had been withdrawn. This was associated with a decrease in % dry weight for the uteri of these animals.     

Regulation of heat shock-induced alterations in the release of prostaglandins by the uterine endometrium of cows

Maternal heat stress in cattle may disrupt pregnancy by elevating uterine prostaglandin F(2alpha) (PGF(2alpha)) secretion. The objectives of this study were to determine the effects of elevated temperature (42 degrees C) in vitro upon 1) prostaglandin secretion by endometrial tissue; 2) the actions of extracellular regulators of uterine PGF [conceptus secretory proteins (bCSPs) and platelet-activating factor, (PAF)]; 3) the activity of the cyclooxygenase-endoperoxidase enzyme complex (PG synthetase); and 4) the activity of the endometrial PG synthesis inhibitor present in the endometrium from pregnant cattle. Endometrial explants at Day 17 of the estrous cycle produced more PGF than PGE(2) while elevated temperature caused increased PGF secretion but did not affect PGE(2) secretion. Elevated temperature did not reduce the ability of bCSPs or PAF to suppress release of PGF. The heat shock-induced increase in PGF at Day 17 was not due to the direct effects on PG synthetase, because PGF production from a cell-free cotyledonary microsomal enzyme preparation was reduced at elevated temperature. The activity of the cytosolic inhibitor of cyclooxygenase present in the endometrium of Day-17 pregnant cows could be reduced but not eliminated at 42 degrees C. We conclude that in vitro heat stress induces PGF secretion from the bovine uterine endometrium at Day 17 after estrus. This increase is not accompanied by the loss of regulatory capacity of conceptus products or increased activity of PG synthetase.