Temporal response of uterine prostaglandins to estradiol treatment in the ovariectomized-prenant rat

Previous studies in our laboratory have shown that 24 hours of estradiol treatment significantly enhanced uterine prostaglandin (PG)F, PGE and thromboxane B₂ (TxB₂) leels but had no effect on 6-Keto-PGF_1α (6KF) concentrations in ovariectomized-pregnant rats. One explanatior for the lack of an augmentation in 6KF was a temporal differences in response (i.e. 6KF increased and decreased within the 24 hour period). To test this possibility rats were ovariectomized on day 19 of pregnancy and sacrificed 0, 4, 8, 12, 16, 20 and 24 hours after estradiol treatment. Uterine tissue and venous plasma were analyzed for PGs by radioimmunoassay. No significant (p > .05) alterations were detected for any of the uterine PGs at 0, 4, 8 and 12 hours. However, at 16 hours PGF, TxB₂ and PGE all showed significant (p > .05) increases (2.4, 3.4 and 2.1 fold, respectively) compared to 12 hours. In contrast, no significant augmentation in 6KF levels (p > .05, 1.3 fold) was detected at 16 compared to 12 hours although it was enhanced relative to 0 and 4 hours. In addition, PGF, TxB₂ and PGE, but not 6KF, showed further increases 24 hours after estradiol administration. No alterations were found (p > .05) for any of the PGs in uterine venous plasma at the time points studied. In summary, uterine PGF, PGE and TxB₂ net production appears to be more enhanced by estradiol treatment than 6KF at the time points studied. In addition, there is a slight, but significant, difference in the temporal response characteristics of 6KF compared to the other PGs. The data suggest that the dramatic increase in uterine PGF, PGE and TxB₂ levels at parturition in the rat are probably significantly related to enhanced levels of estradiol. However, the majority of the increase in uterine 6KF levels at labor is more likely caused by factors other than augmented plasma estradiol.     

Effects of the fetal-placental unit on uterine prostaglandin levels at term in the pregnant rat

Uterine prostaglandins (PGs) increase markedly at term in the pregnant rat. To assess the contribution of the fetal-placental unit (FPU) on uterine tissue and uterine venous blood PG concentrations, each uterine horn of 14 unilaterally pregnant rats at day 21 of pregnancy were compared. In addition, 7 bilaterally pregnant rats were studied. Uterine tissue and uterine venous plasma PGF, PGE, 6-Keto-PGF1 (6KF) and thromboxane B2 (TxB2) and systemic plasma progesterone, estradiol and estrone were determined by radioimmunoassay. Uterine concentrations of PGs (ng/mg DNA) were always greater on the pregnant side of unilaterally pregnant rats (p less than .05) although the PGF levels were elevated to a lesser extent than were PGE, TxB2 or 6KF. However, no differences were detected between uterine tissue from the pregnant side of unilaterally pregnant compared to bilaterally pregnant rats. In addition, no differences were found in uterine venous plasma PGs adjacent or opposite the pregnant uterine horn and in systemic plasma progesterone, estradiol and estrone levels in unilaterally vs bilaterally pregnant rats. These data suggest that the presence of the FPU is associated with an increased capacity of uterine tissue to produce PGE, TxB2 and 6KF, and to a lesser degree PGF, and thus may contribute to the increase in uterine PGs periparturition.     

Contributions of the fetoplacental unit to augmented uterine prostaglandin levels periparturition in the rat

The purpose of the present study was to determine if the acute alterations in uterine prostanoid levels at the end of pregnancy are influenced locally by the fetoplacental unit (FPU). Unilaterally pregnant rats were killed on Days 20 and 21 of pregnancy (delivery = Day 21.5) and uterine tissue was removed and analyzed for prostaglandin (PG) E, PGF, thromboxane B2 (TxB2), and 6-keto-PGF1 alpha (6KF) by radioimmunoassay. A significant (P less than 0.05) main effect of Day (20 vs. 21) and Uterine Horn (nonpregnant vs. pregnant), but no interaction for PGE, PGF, and TxB2 was detected. In contrast, a significant interaction (P less than 0.05) of Day with Uterine Horn was found for uterine 6KF levels. Examination of the simple main effects indicated an enhanced level (P less than 0.05) of 6KF in uterine tissue adjacent compared to opposite the FPU at Days 20 and 21. However, uterine 6KF levels in the nonpregnant, but not pregnant, uterine horn were greater at Day 21 compared to Day 20 of pregnancy. The lack of a significant interaction of the main effects for PGE, PGF, and TxB2 suggests that the increased levels of these PGs between Days 20 and 21 were proportional in the nonpregnant and pregnant uterine horn. Therefore, the factor(s) responsible for the augmentation in these uterine PG levels between Days 20 and 21 is(are) most likely arriving via systemic circulation. In addition, the proportionate increases in uterine PGs imply that the FPU is not conferring upon adjacent uterine tissue any unique ability to respond to systemic factors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of the fetal-placental unit on uterine prostaglandin levels at term in the pregnant rat

Uterine prostaglandins (PGs) increase markedly at term in the pregnant rat. To assess the contribution of the fetal-placental unit (FUP) on uterine tissue and uterine venous blood PG concentrations, each uterine horn of 14 unilaterally pregnant rats at day 21 of pregnancy were compared. In addition, 7 bilaterally pregnant rats were studied. Uterine tissue and uterine venous plasma PGF, PGE, 6-Keto-PGF₁ (6KF) and thromboxane B₂ (TxB₂) and systematic plasma progesterone, estradiol and estrone were determined by radioimmunoassay. Uterine concentrations of PGs (ng/mg DNA) were always greater on the pregnant side of unilaterally pregnant rats (p<.05) although the PGF levels were elevated to a lesser extent than were PGE, TxB₂ or 6KF. However, no differences were detected between uterine tissue from the pregnant side of unilaterally pregnant compared to bilaterally pregnant rats. In addition, no differences were found in uterine venous plasma PGs adjacent or opposite the pregnant uterine horn and in systematic plasma progesterone, estradiol and estrone levels in unilaterally vs bilaterally pregnant rats. These data suggest that the presence of the FPU is associated with an increased capacity of uterine tissue to produce PGE, TxB₂ and 6KF, and to a lesser degree PGF, and thus may contribute to the increase in uterine PGs periparturition.     

Arachidonic acid metabolites in a nephroblastoma associated with paraneoplastic hypercalcemia

Blood concentration of PGE2, F2a, 6 keto PGF1a (6kF1a), TxB2 and 13, 14 dehydro 15 keto PGE2 (13, 14 OH 15 k E2) were measured in renal artery and vein of a patient with a PGs producing nephroblastoma. The tumor tissue produced PGs in the following order: PGF2a greater than PGE2 greater than TxB2 greater than 6kF1a greater than 13, 14 OH 15 k E2. However, renal artery concentration of the substances were as follows: 13, 14 OH 15 k E2 greater than TxB2 greater than 6kF1a greater than PGF2a greater than PGE2. Since arterial concentration is critical to postulating a calcium mobilizing effect on bone tissue, PGE2 arterial level seems to be too low to exert a pathogenetic role on hypercalcemia, at least in the patient reported here.     

Alterations in uterine and placental prostaglandin F and E with gestational age in the rat

Experiments were designed to determine the chronological alterations in placental and uterine prostaglandin F and E (PGF and PGE) during pregnancy in the rat. Pregnant rats (sperm in the vagina = day 0) were sacrified at days 15, 18,19, 20, 21 and delivery (day 21 ) and placental and uterine tissues assayed (RIA) for PGF and PGE immediately (“ ”) or after 1 hour incubation (“ ”). Uterine content of PGF and PGE (ng PG/mg DNA) was increased significantly by day 19 and further increases were seen through delivery. Incubation of uterine tissue resulted in enhanced net production of PGF and PGE (p <.05) per mg DNA (as judged by tissue content and release into the incubation medium) by day 18 of pregnancy vs. day 15. Net production peaked around the time of delivery thus paralleling the alterations in tissue content .By contrast, no differences with gestational age were found in placental content of PGF and PGE , the concentrations throughout late gestation remaining in the range of uterine PGs at day 15. However, production of PGs per mg placental DNA increased markedly during incubation with significant enhancement detected by day 19 vs. 15, achieving levels even greater than the uterus .The and findings for the uterus are consistent with the hypothesis that increases in uterine PGs levels at the end of pregnancy may play an important role in parturition. The experiences with placental tissue suggest that the potential for PG production per placental cell may also increase in late gestation and thereby contribute to the augmented intrauterine availability of PGs at that time.     

Influences of estradiol and of catechol and non-catechol estrogens on the output of prostaglandins in uteri from spayed rats

The effects of 17-beta estradiol and of some catechol and non-catechol-estrogens on the synthesis and output of prostaglandins (PGs) E and F by uteri from ovariectomized rats, were explored. Uteri from castrated animals released twice as much PGE than PGF. When uterine tissue was obtained from spayed rats injected prior to sacrifice with a low dose of 17-beta estradiol (0.5 + 1.0 microgram, on two consecutive days), the output of PGE diminished significantly. With a higher dose of the hormone (0.5 + 50.0 micrograms) the depressive influence on the synthesis and release of PGE was even more marked, whereas the output of PGF rose significantly. Low or high doses of estrone or of estriol failed to affect the release of either one of the PGs determined. On the other hand, 2-0H-estradiol at a low dose had no action but at a higher one inhibited the release of PGE without influencing PGF. Neither low nor high doses of 2-0H estriol or of 2-0H estrone affected the synthesis and release of uterine PGs. It was also observed that all the compounds tested evoked a significant uterotrophic action. It appears plausible that some catechol metabolites of 17-beta estradiol, but not other catechol-estrogens, could be involved in the mechanism of action of 17-beta estradiol modulating the production of PGs by the rat uterus.     

The urinary excretion of prostaglandins and thromboxane B2 in healthy volunteers: a study in males and females, and on the influence of seminal fluid contamination

Radioimmunoassay measurements of prostaglandins (PGs) E2, F2 alpha, 6-keto-PGF1 alpha and thromboxane (Tx) B2 in 24 h urine specimens from a male and a female healthy volunteer on several consecutive days revealed a dramatic increase of PGE2, PGF2 alpha, 6-keto-PGF1 alpha on days, upon which they had sexual intercourse; only TxB2 remained stable. Furthermore, the PGE2/PGF2 alpha ratio rose to values greater than 0.5 on days with sexual intercourse. This was found to be due to contamination of the urine samples by seminal fluid. Two 24 h urine samples from each of 26 healthy male and female volunteers (HV) revealed higher (p less than 0.01) mean PGE2 and PGF2 alpha values in males than in females. The results show that the interpretation of the urinary PG excretion as a measure of renal PG synthesis should be considered carefully, and that a PGE2/PGF2 alpha ratio greater than 0.5 indicates probable seminal contamination of urine.     

Arachidonic acid metabolites in a nephroblastoma associated with paraneoplastic hypercalcemia

Blood concentration of PGE2, F2a, 6 keto PGF1a (6kF1a), TxB2 and 13, 14 dehydro 15 keto PGE2 (13, 14 OH 15 k E2) were measured in renal artery and vein of a patient with a PGs producing nephroblastoma. The tumor tissue produced PGs in the following order: PGF2a>PGE2>TxB2>6kF1a>13, 14 OH 15 k E2. However, renal artery concentration of the substances were as follows: 13, 14 OH 15 k E2>TxB2>6kF1a>PGF2a>PGE2. Since arterial concentration is critical to postulating a calcium mobilizing effect on bone tissue, PGE2 arterial level seems to be too low to exert a pathogenetic role on hypercalcemia, at least in the patient reported here.     

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.     

Oxytocin enhances the basal release of uterine prostaglandin F2 alpha, but not that of PGE1, or of PGE2, and changes the metabolism of exogenous arachidonate, favouring the formation of prostaglandin F2 alpha and 5-HETE. Relationships with its uterotonic action and modulation by estradiol

We attempted to explore possible mechanism(s) subserving the influence of oxytocin on uterine motility by studying the action of the hormone on: 1) the contractile activity of isolated rat uteri in the presence or absence of indomethacin; 2) the synthesis and release of prostaglandins (PGs) into the solution incubating the uterine tissue as well as the metabolism of labelled arachidonic acid; 3) the uptake of 45Ca2+ by uterine strips. The experiments were bone with uterine preparations isolated from spayed rats treated or not with 17-beta-estradiol. The values of isometric developed tension (IDT) and of frequency of contractions (FC) induced by oxytocin in uterine strips isolated from spayed and spayed-estrogenized rats, were not modified by indomethacin at 10(-6) M. On the other hand, uterine strips from untreated spayed rats, release into the incubating medium approximately equal amounts of PGE1, PGE2 and PGF2 alpha. The in vitro presence of oxytocin (50 mU/ml) increased significantly (p 0.05) the output of PGF 2 alpha without changing the release of PGE1 or PGE2. Uteri from spayed rats injected prior to sacrifice with 17-beta-estradiol released significantly less PGE1 and PGE2 (p less than 0.005) than preparations from non-injected animals, whereas the output of PGF2 alpha in the suspending solution remained unchanged. Following estrogenization the addition of oxytocin to preparations obtained from spayed-estrogenized rats also increased the output of uterine PGF2 alpha (p less than 0.001) without changing that of PGs E1 or E2.(ABSTRACT TRUNCATED AT 250 WORDS)     

A novel anti-lipolytic action of norepinephrine in uteri isolated from spayed rats appears subserved by the activation of alpha 1-adrenoreceptors diminishing the generation and release of lipolytic prostaglandins

The effects of norepinephrine (NE: 3 x 10(-6) M) on the outputs of prostaglandins (PGs) E1, E2 and F2 alpha, from uterine horns isolated from ovariectomized rats and suspended in solutions with or without exogenous glucose, were explored. The releases of the different PGs into the external medium were determined after incubating for one hour uterine preparations, mounted within a tissue bath and receiving a constant preload tension. In glucose-containing solutions, NE enhanced the basal output of PGE2 and failed to alter the basal releases of PGE1 or of PGF2 alpha. In glucose-free media, the basal output of PGE2 was comparable to that detected in presence of exogenous glucose, and its augmentation following added NE was again evident. However, the basal outputs of PGE1 and of PGF2 alpha, greater in glucose-free solutions than in glucose-containing media, were significantly diminished by added NE. Uterine triglyceride (TG) levels were also explored, both immediately after sacrifice (0 min) or following suspending uterine segments during one hour (60 min) in solutions containing exogenous glucose or not. In glucose-containing media, tissue TGs did not differ at 0 min or at 60 min, neither in controls, nor in NE-challenged preparations, whereas in glucose-free solutions, TGs were significantly smaller at 60 min than at 0. interestingly, the addition of NE completely prevented the dimunition of uterine TGs, present at 60 min in glucose-free medium. Neither propranolol nor yohimbine (10(-6) M) altered this sparing action of added NE on tissue TGs, but phentolamine or prazocin (10(-6) M), effectively antagonized the preventive effect of the agonist.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uteroplacental production of eicosanoids in ovine pregnancy

Dramatic cardiovascular alterations occur during normal ovine pregnancy which may be associated with increased prostaglandin production, especially of uteroplacental origin. To study this, we examined (Exp 1) the relationships between cardiovascular alterations, e.g., the rise in uterine blood flow and fall in systemic vascular resistance, and arterial concentrations of prostaglandin metabolites (PGEM, PGFM and 6-keto-PGF1 alpha) in nonpregnant (n = 4) and pregnant (n = 8) ewes. To determine the potential utero-placental contribution of these eicosanoids in pregnancy, we also studied (Exp 2) the relationship between uterine blood flow and the uterine venous-arterial concentration differences of PGE2, PGF2 alpha, PGFM, 6-keto-PGF1 alpha, and TxB2 in twelve additional late pregnant ewes. Pregnancy was associated with a 37-fold increase in uterine blood flow and a proportionate (27-fold) fall in uterine vascular resistance (p less than 0.01). Arterial concentrations of PGEM were similar in nonpregnant and pregnant ewes (316 +/- 19 and 245 +/- 38 pg/ml), while levels of PGFM and PGI2 metabolite 6-keto-PGF1 alpha were elevated 23-fold (31 +/- 14 to 708 +/- 244 pg/ml) and 14-fold (12 +/- 4 to 163 +/- 78 pg/ml), respectively (p less than 0.01). Higher uterine venous versus uterine arterial concentrations were observed for PGE2 (397 +/- 36 and 293 +/- 22 pg/ml) and 6-keto-PGF1 alpha (269 +/- 32 and 204 +/- 32 pg/ml), p less than 0.05, but not PGF2 alpha or TxB2. Although PGFM concentrations appeared to be greater in uterine venous (1197 +/- 225 pg/ml) as compared to uterine arterial (738 +/- 150 pg/ml) plasma, this did not reach significance (0.05 less than p less than 0.1). In normal ovine pregnancy arterial levels of PGI2 are increased, which may in part reflect increased uteroplacental production. Moreover the gravid ovine uterus also appears to produce PGE2 and metabolize PGF2 alpha.     

Prostaglandins enhance parathyroid hormone-evoked increase in free cytosolic calcium concentration in osteoblast-like cells.

Prostaglandins (PGs) are autocrine or paracrine hormones that may interact with circulating hormones such as parathyroid hormone (PTH) in bone. We examined the interaction of the PGs, PGF2 alpha, PGE2, and 6-keto-PGF1 alpha with PTH to enhance the rapid, initial transient rise in free cytosolic calcium ([Ca2+]i) and cAMP levels stimulated by PTH. Pretreatment of UMR-106, MC3T3-E1, and neonatal rat calvarial osteoblast-like cells by PGs resulted in an enhancement of the early transient rise in [Ca2+]i stimulated by PTH. PGF2 alpha was approximately 100 times more potent than PGE2. PGE2 itself was more potent than 6-keto-PGF1 alpha in enhancing PTH-stimulated rise in [Ca2+]i. Near-maximal augmentation was achieved at PGF2 alpha doses of 10 nM and PGE2 of 1 microM. The degree of augmentation in [Ca2+]i by PGF2 alpha was independent of preincubation time. PGF2 alpha pretreatment did not alter the EC50 for the PTH-induced [Ca2+]i increase but only the extent of rise in [Ca2+]i at each dose of PTH. The augmented increase in [Ca2+]i was mostly due to enhanced PTH-mediated release of Ca2+ from intracellular stores. PGF2 alpha did not stimulate an increase in PTH receptor number as assessed by [125I]-PTH-related peptide binding. PG pretreatment partially reversed PTH inhibition of cell proliferation, suggesting that an increase in [Ca2+]i may play a role in tempering the anti-proliferative effect of PTH mediated by cAMP. These studies suggest a new mode by which PGs can affect cellular activity.     

Effects of experimental diabetes on spontaneous contractions, on the output of prostaglandins and on the metabolism of labelled arachidonic acid, in uteri isolated from ovariectomized rats. Influences of estradiol

Spontaneous changes in isometric developed tension (IDT) as a function of time after isolation (contractile constancy) in uteri from control-castrated and castrated chronic streptozotocin-diabetic rats, were explored. The effects of injecting 17-beta estradiol (Eo) were also studied. No differences in the minor changes of contractile constancy, between control and diabetic preparations, during a period of 60 min, were detected, whereas uteri from non-diabetic Eo injected animals (0.5 + 1.0 ug, prior to sacrifice), exhibited a profound reduction of IDT, significantly greater than in tissues obtained from Eo injected-diabetic rats. Moreover, basal generation and outputs into the suspending solution of prostaglandins (PGs) E1, E2 and F2 alpha, were explored in the same groups, at 60 min following tissue isolation. The basal outputs of these three PGs were similar in castrated control rats, but preparations from castrated-diabetics released significantly more PGE1. The administration of Eo to castrated-diabetics, failed to alter the releases of the three PGs explored. In addition, the metabolism of labelled arachidonic acid (AA) into different prostanoids (6-keto-PGF1, PGF2, PGE2 and thromboxane B2-TXB2), was also investigated. The non-diabetic spayed rat uterus converted AA into these four prostanoids, the transformation into 6-keto-PGF1 alpha (as an index of PGI2 formation) being the most prominent. In preparations from diabetic rats the formation) being the most prominent. In preparations from diabetic rats the formation of 6-keto-PGF1 alpha, PGF2 alpha and PGE2, was significantly smaller than in controls, whereas a greater % of TXB2 formation (as an index of TXA2), was detected. On the other hand uterine preparations from non-diabetic spayed rats injected with Eo formed less 6-keto-PGF1 alpha and PGE2 and similar amounts of PGF2 alpha or of TXB2 from AA, than Eo injected controls, whereas uteri from castrated diabetic animals injected with Eo, formed a similar % of 6-keto-PGF1 alpha, PGF2 alpha and PGE2 from AA, than tissue preparations from non-estrogenized controls. However, the enhanced transformation of the labelled fatty acid precursor (AA) into TXB2 in the diabetic group, was significantly reduced by the steroid. The role of the augmented generation and release of PGE1 in uteri from diabetic rats is discussed in terms of precedents indicating the relevance of PGs type E supporting rat uterine motility. In addition the influence of Eo is attractive, because its reducing effect on TX production, in diabetes, a disease known to be accompanied by enhanced synthesis of vasoconstrictor and platelet aggregation TXA2, and by frequent obstructive circulat     

Effect of decidual tissue on the uterine production of prostaglandins in pseudopregnant rats.

The concentration of prostaglandin F (PGF) in uterine vein plasma of non-traumatized pseudopregnant rats and pseudopregnant rats with deciduomata were not significantly different from each other at any of the times of pseudopregnancy studied (Days 7, 10 and 12). There was a significant increase in PGF levels on Day 10 in both groups of pseudopregnant animals (P less than 0-05) compared to the Day 4 values, and PGE values were significantly greater on Day 10 in the decidual tissue-bearing rats (P less than 0-01). A slight but not significant elevation in PGE concentration was observed on Days 7 and 12 in rats with deciduomata, but there was no significant difference in the control rats on Days 4, 7, 10 or 12. The results indicate that the prolongation of pseudopregnancy in rats with deciduomata is not due to a decreased production of uterine PGs and lend support to the recent suggestion of a luteotrophic effect of decidual tissue in the rat.     

In vitro effects of progesterone and estradiol on uterine prostaglandin production in the pregnant rat.

Uterine prostaglandin (PG) levels increase markedly at the end of pregnancy in the rat and steroid hormones appear to be important regulators of this augmentation. The purpose of the present study was to examine the in vitro effects of progesterone (P) and estradiol (E2) on uterine PGE and PGF production in the pregnant rat. Uterine tissue was removed at Days 19 and 21 of pregnancy and incubated with P or E2 (0.1, 1, 10, 100, and 1,000 ng/ml) for 48 h in Ham's F-10 medium at 37 degrees C. P significantly (p less than 0.05) inhibited PGE and PGF production in a dose-dependent manner at Day 19, but not at Day 21 of pregnancy. In contrast, E2 had no effect (p greater than 0.05) at either day of pregnancy. In a second study, P was found to inhibit uterine PGE production at Days 15 and 19, but not at Day 21 or at delivery. A third study determined that the levels of P were greatly reduced in media containing uterine tissue from delivery when compared to media containing tissue from day 15 of pregnancy (p less than 0.05). In a fourth experiment, no difference in tritium-labeled P uptake was detected between media containing uterine tissue from Day 15 of pregnancy and media containing uterine tissue removed at delivery. This observation in association with data from the literature suggests that the disappearance of P from the media in experiment 3 might be due to enhanced P metabolism rather than to differential uptake of P by the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterine and placental prostaglandins and their modulation of oxytocin sensitivity and contractility in the parturient uterus

The parturient uterus develops a markedly enhanced sensitivity to the uterotonic action of oxytocin (OT). The mechanism leading to this enhanced OT sensitivity is not known. Our previous work suggested that prostaglandins (PGs) may be involved. To define the relationship between OT sensitivity and uterine PG production, we measured uterine sensitivity to OT by a quantitative dose-response procedure in rats on Days 19, 20, 21 and 22 of pregnancy and monitored uterine and placental tissue concentrations of PGF2 alpha and PGE2. In addition, we determined the effects of inhibition of endogenous PG synthesis on OT sensitivity and uterine contractility. We found that both OT sensitivity and spontaneous contractility are positively related to uterine PGF2 alpha production. An abrupt increase in OT sensitivity was observed on Days 21 and 22 of pregnancy. The increase in OT sensitivity was coincidental with the marked increase in PGF2 alpha production in the uterus on Days 21 and 22 of pregnancy. Suppression of in vivo PG synthesis caused a reduction in both spontaneous uterine contractility and OT-induced contractions. Uterine PGE2 concentrations and release were 3-5 times lower than PGF2 alpha. There were no significant fluctuations of uterine PGE2 concentration measured on these last 4 days of gestation. Placental PG levels were also found not to be related to uterine contractility. Placental PGE2 levels were higher than PGF2 alpha and may play a regulatory role in placental perfusion. However, placental PGs did not vary with gestational age.     

Progesterone reduces erectile dysfunction in sleep-deprived spontaneously hypertensive rats

Background

The rate-limiting step in prostaglandin (PG) biosynthesis is catalyzed by phospholipase A2 (PLA2) enzymes which hydrolyze arachidonic acid from membrane phospholipids. Despite their importance in uterine PG production, little is known concerning the specific PLA2 enzymes that regulate arachidonic acid liberation in the uterine endometrium. The objectives of this study were to evaluate the expression and activities of calcium-independent Group VI and Group IVC PLA2 (PLA2G6 and PLA2G4C) and calcium-dependent Group IVA PLA2 (PLA2G4A) enzymes in the regulation of bovine uterine endometrial epithelial cell PG production.

Methods

Bovine endometrial epithelial cells in culture were treated with oxytocin, interferon-tau and the PLA2G6 inhibitor bromoenol lactone, alone and in combination. Concentrations of PGF2alpha and PGE2 released into the medium were analyzed. Western blot analysis was performed on cellular protein to determine the effects of treatments on expression of PLA2G4A, PLA2G6 and PLA2G4C. Group-specific PLA2 activity assays were performed on cell lysates following treatment with oxytocin, interferon-tau or vehicle (control), alone and in combination. To further evaluate the role of specific PLA2 enzymes in uterine cell PG biosynthesis, cells were transfected with cDNAs encoding human PLA2G6 and PLA24C, treated as described above and PG assays performed.

Results

Constitutive cell production of PGF2alpha was about two-fold higher than PGE2. Oxytocin stimulated production of both PGs but the increase of PGF2alpha was significantly greater. Interferon-tau diminished oxytocin stimulation of both PGs. The PLA2G6 inhibitor, bromoenol lactone, abolished oxytocin-stimulated production of PGF2alpha. Treatments had little effect on PLA2G4A protein expression. In contrast, oxytocin enhanced expression of PLA2G6 and this effect was diminished in the presence of interferon-tau. Expression of PLA2G4C was barely detectable in control and oxytocin treated cells but it was enhanced in cells treated with interferon-tau. Oxytocin stimulated PLA2 activity in assays designed to evaluate PLA2G6 activity and interferon-tau inhibited this response. In assays designed to measure PLA2G4C activity, only interferon-tau was stimulatory. Cells overexpressing PLA2G6 produced similar quantities of the two PGs and these values were significantly higher than PG production by non-transfected cells. Oxytocin stimulated production of both PGs and this response was inhibited by interferon-tau. Bromoenol lactone inhibited oxtocin stimulation of PGF2alpha production but stimulated PGE2 production, both in the absence and presence of oxytocin. Cells over-expressing PLA2G4C produced more PGE2 than PGF2alpha and interferon-tau stimulated PGE2 production.

Conclusion

Results from these studies indicate that oxytocin stimulation of uterine PGF2alpha production is mediated, at least in part, by up-regulation of PLA2G6 expression and activity. In addition to its known inhibitory effect on oxytocin receptor expression, interferon-tau represses oxytocin-stimulated PLA2G6 expression and activity and this contributes to diminished PGF2alpha production. Furthermore, endometrial cell PGE2 biosynthesis was associated with PLA2G4C expression and activity and interferon-tau was stimulatory to this process.     

Prostaglandin E and E2 alpha secretion by glandular and stromal cells of the pig endometrium in vitro: effects of estradiol-17 beta, progesterone, and day of pregnancy.

Prostaglandins (PGs) are believed to play important roles in the establishment of pregnancy. Glandular and stromal cells were isolated from pig endometrium on days 11 through 19 of pregnancy and cultured in the presence of estradiol-17 beta (E2) and progesterone (P4) to determine the effect of day of pregnancy and steroids on the secretion of PGE and PGF2 alpha. Estradiol at concentrations between .01 and 1 microM did not affect PGE and PGF2 alpha secretion into the medium by glandular and stromal cells. Progesterone (.1 microM) suppressed (P less than .001) PGE and PGF2 alpha production from both cell types. Glandular cells secreted more (P less than .01) PGF2 alpha than PGE, whereas stromal cells collected on days 11, 12, 13, and 19 secreted more (P less than .05) PGE than PGF2 alpha. Stromal cells isolated from tissues collected on day 13 of pregnancy produced PGs with higher (P less than .01) PGE:PGF2 alpha ratio than those from tissues harvested on other days of pregnancy. Glandular cells isolated from tissues collected on days 13 and 19 and stromal cells isolated from tissue collected on day 13 of pregnancy secreted more (P less than .05) PGE and PGF2 alpha than cells isolated on other days of pregnancy. We conclude that: 1) P4 has a suppressing effect on PG secretion; 2) endometrial glandular and stromal cells each produce a unique profile of PGs; and 3) endometrial cells harvested on different days of pregnancy secrete different amounts of PGE and PGF2 alpha.