The effect of endogenous and exogenous estradiol-17beta on the release of prostaglandin F2alpha from the ovine uterus

Effect of dose of estradiol-17β on prominence of an induced 13,14-dihydro-15-keto-PGF(2α) (PGFM) pulse and relationship of prominence to progesterone, LH, and luteal blood flow in heifers

Various doses of estradiol-17β (E(2)) were used in heifers to induce a pulse of 13,14-dihydro-15-keto-prostaglandin F(2α) (PGFM). The effect of E(2) concentration on the prominence of PGFM pulses and the relationship between prominence and intrapulse concentration of progesterone (P(4)), LH, and luteal blood flow were studied. A single dose of 0 (vehicle), 0.01, 0.05, or 0.1 mg of E(2) was given (n = six/group) 14 d after ovulation. Blood samples were collected, and luteal blood flow was evaluated hourly for 10 h after the treatment. The 0.05-mg dose increased and the 0.1-mg dose further increased the prominence of the induced PGFM pulse, compared with the 0.0-mg dose and the 0.01-mg dose. The PGFM pulses were subdivided into three different prominence categories (<50, 50 to 150, and >150 pg/mL at the peak). In the 50 to 150 category, P(4) concentration increased (P < 0.05) between -2 h and 0 h (0 h = peak of PGFM pulse). In the >150 category, P(4) decreased (P < 0.05) between -1 h and 0 h, LH increased (P < 0.05) at 1 h, and luteal blood flow apparently decreased (P < 0.05) at 2 h of the PGFM pulse. The novel results supported the following hypotheses: (1) an increase in E(2) concentration increases the prominence of a PGFM pulse, and (2) greater prominence of a PGFM pulse is associated with a greater transient intrapulse depression of P(4) at the peak of the PGFM pulse. In addition, the extent of the effect of prostaglandin F(2α) on the increase in LH and changes in blood flow within the hours of a PGFM pulse was related positively to the prominence of the PGFM pulse.

Pre-puberal plasma luteinizing hormone concentrations and progesterone concentrations during the oestrous cycle and early pregnancy in Galway and Fingalway female lambs

Twenty-four young female sheep, 12 Galways and 12 Fingalways, were used to study the effects of breed and level of nutrition on pre-puberal plasma luteinizing hormone and progesterone concentrations throughout the oestrous cycle and during the first 35 days of pregnancy. The sheep were spring-born and were housed at the end of July when they weighed approx. 34 kg. Equal numbers of animals from each breed were fed on a concentrate diet either ad libitum or at a restricted level that was slightly above their estimated maintenance requirements. The Fingalways reached puberty 1 month earlier than the Galways (11 October ±4 days v. 10 November ±5 days). The restricted animals tended (P < 0·10) to reach puberty later than those fed ad libitum (1 November ±5 days v. 20 October ±4 days). Breed differences in the mean level of plasma progesterone on any day of the oestrous cycle were not significant. The mean daily plasma progesterone concentration was similar for the animals on the two planes of nutrition throughout the cycle, with the exception of day 11 when those fed ad libitum had a significantly higher level (P < 0·01). Plasma progesterone levels in the pregnant females between 5 and 35 days post mating were generally higher in Fingalways than in Galways and were not influenced by plane of nutrition. Plasma luteinizing hormone levels tended to be higher, during the 7 weeks before puberty, in Fingalways than in Galways and in animals fed ad libitum than in those on the restricted level of feeding.

Significance of maternal uterine proteins in the establishment of pregnancy

Mammalian embryonic development depends on extrinsic support by the maternal organism. During the preimplantation period the growing blastocyst needs favourable environmental conditions, which are provided by endometrial transformations and secretion. The macromolecular composition of uterine secretion at different times before implantation is characterized by a spectrum of protein patterns which change daily. In an attempt to shed light on the significance of the uterine secretion proteins, particularly uteroglobin in the rabbit, in the establishment of early pregnancy, analyses are reported which demonstrate the origin and endocrine control of the synthesis and release of these proteins. In a comparative study of blastocyst development in vivo and in vitro the significance and consequences of asynchrony between the embryonic and maternal reproductive phases are investigated. Particular attention is drawn to uterine influences on the rabbit blastocyst coverings, and how embryonic development can be retarded by abnormal structural transformation of the zona pellucida and the mucin coat. Finally, the covenient experimental systems of pseudopregnancy and of delayed uterine secretion in the rabbit permit an approach the question of whether the uterine macromolecular components constitute a maternal response to the presence of the as yet unimplanted blastocyst.

Antiluteolytic effect of the embryo

In several mammalian species, prostaglandin F2 alpha (PGF2 alpha) released from the uterus causes corpus luteum regression, and thereby regulates the length of the oestrous cycle or pseudopregnancy. If the animal becomes pregnant, luteal regression must be prevented since ovarian progesterone is necessary for pregnancy maintenance during at least the first one-third of pregnancy. Evidence is presented that the guinea-pig conceptus produces an antiluteolytic factor which suppresses PGF2 alpha output from the uterus by preventing the increase in uterine PGF2 alpha-synthesizing capacity which occurs around the time of luteolysis. Experiments in unilaterally pregnant guinea-pigs, with either an intact or a transected sterile horn, indicate that this factor acts both locally systemically, though separation of the two uterine horns does greatly reduce its effect on the sterile side. Oestradiol administered during early pregnancy induces abortion, which is associated with a high PGF2 alpha-synthesizing capacity of the uterus. However, luteal regression does not take place while the conceptuses are in the uterus. Spontaneously aborting guinea-pigs behave similarly. The conceptus may therefore secrete a luteotrophic hormone as well. Luteal maintenance during early pregnancy in other species is discussed, since experiments on sheep indicate that the sheep embryo may also secrete an antiluteolytic factor.

Dynamic in vivo changes in tissue inhibitors of metalloproteinases 1 and 2, and matrix metalloproteinases 2 and 9, during prostaglandin F(2alpha)-induced luteolysis in sheep

Prostaglandin F(2alpha) (PGF(2alpha)) typically initiates a cascade of events that leads to the functional and structural demise of the corpus luteum. A sheep model was used in which a 1-h, systemic infusion of PGF(2alpha) (20 microg/min) is given at midcycle. Such an infusion mimics the onset of spontaneous luteolysis by causing a transient decrease in peripheral plasma progesterone, which reaches a nadir ( approximately 60% of controls) at 8 h but returns to control levels by 16-24 h. We investigated whether PGF(2alpha) also influenced the endogenous protein levels of tissue inhibitors of metalloproteinases, TIMP-1 and TIMP-2, and matrix metalloproteinases, MMP-2 and MMP-9, all of which have been implicated in remodeling of the extracellular matrix (ECM). Corpora lutea (Day 11) were collected at 0 h and at 1, 8, 16, and 24 h post-PGF(2alpha) infusion (n = 3 sheep at each time). Immunoblot analysis revealed an immediate and precipitous decline in TIMP-1 (30 kDa) and TIMP-2 (19 kDa) protein levels (60% and 90%, respectively; P < 0.05) at the 1-h time point and remained depressed at 8 h (P < 0.05). Gelatin zymography and other procedures identified three MMPs (85, 70, and 64 kDa), which were shown to be the latent form of MMP-9 and the active and latent forms of MMP-2, respectively. In contrast to the rapid decrease in TIMP-1 and -2 levels, an increase in MMP-2 activity (165% of controls, P < 0.05) occurred at 8 h, which corresponded to the nadir in plasma progesterone. These early changes in TIMPs and MMPs indicate that alterations in the structure of the ECM by PGF(2alpha) may play a hitherto unsuspected role in the subsequent process of functional luteolysis.

Cellular mechanisms by which oxytocin mediates ovine endometrial prostaglandin F2alpha synthesis: role of G(i) proteins and mitogen-activated protein kinases

Oxytocin stimulates a rapid increase in ovine endometrial prostaglandin (PG) F2alpha synthesis. The overall objective of these experiments was to investigate the cellular mechanisms by which oxytocin induces endometrial PGF2alpha synthesis. The objective of experiment 1 was to determine whether G(i) proteins mediate oxytocin-induced PGF2alpha synthesis. Uteri were collected from four ovary-intact ewes on Day 14 postestrus. Caruncular endometrial explants were dissected and subjected to in vitro incubation. Pertussis toxin, an inhibitor of G(i) proteins, had no effect on the ability of oxytocin to induce PGF2alpha synthesis (P > 0.10). The objective of experiment 2 was to determine whether any of the three mitogen-activated protein kinases (MAPKs), extracellular signal regulated protein kinase (ERK1/2), c-Jun N-terminal/stress-activated protein kinase (JNK/SAPK), or p38 MAPK, mediate oxytocin-induced PGF(2alpha) synthesis. Eleven ovary-intact ewes were given an injection of oxytocin (10 IU; i.v.; n = 5) or physiological saline (i.v.; n = 6) on Day 15 postestrus. Uteri were collected 15 min after injection and caruncular endometrium was dissected. Endometrial homogenates were prepared and subjected to Western blotting. Membranes were probed for both total and phosphorylated forms of all three classes of MAPK. All classes of MAPK were detected in ovine endometrium, but oxytocin treatment had no effect on the expression of these proteins (P > 0.10). ERK1/2 was the only phosphorylated MAPK detected and its concentrations were higher in oxytocin-treated ewes (P < 0.01). The objective of experiment 3 was to further investigate the role of ERK1/2 during oxytocin-induced PGF2alpha synthesis. Uteri were collected from four ovary-intact ewes on Day 14 postestrus. Caruncular endometrial explants were dissected and subjected to in vitro incubation. PD98059, a specific inhibitor of ERK1/2 activity, blocked the ability of oxytocin to stimulate PGF(2alpha synthesis in a dose-dependent manner (P < 0.05). These results indicate that the ovine oxytocin receptor is not coupled to G(i) proteins. These results indicate that oxytocin induces phosphorylation of ERK1/2 and that this MAPK appears to mediate oxytocin-induced PGF2alpha synthesis in ovine endometrium.

Effect of oxytocin on expression of cytosolic phospholipase A2 mRNA and protein in ovine endometrial tissue in vivo

The induction of endometrial prostaglandin (PG) F2alpha synthesis by oxytocin is dependent upon activation of phospholipase (PL) A2 and mobilization of arachidonic acid. The objective of this study was to determine if oxytocin stimulates PGF2alpha synthesis by inducing synthesis of cytosolic PLA2 (cPLA2). In Experiment 1, 15 ovariectomized ewes were given progesterone and estradiol to simulate an estrous cycle. Ewes were then given an injection of oxytocin on Day 14 of the simulated estrous cycle. Jugular blood samples were collected and assayed for 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM). Uteri were collected at 0, 7.5, 25, 90, or 240 min postinjection (n = 3 ewes/time point). Total RNA was isolated from caruncular endometrium and subjected to dot-blot analysis. Oxytocin induced a rapid and transient increase in serum PGFM (P < 0.01). However, endometrial concentrations of cPLA2 mRNA did not change following oxytocin administration (P > 0.10). In Experiment 2, 11 ovary-intact ewes were given oxytocin (n = 5) or saline (n = 6) on Day 15 after estrus. Jugular blood samples were collected and assayed for serum concentrations of PGFM. Uteri were collected at 15 min postinjection. Homogenates were prepared from caruncular endometrium and subjected to Western blot analysis. Concentrations of PGFM were higher in oxytocin treated ewes compared to saline treated ewes at 15 min postinjection (P < 0.01). Endometrial concentrations of cPLA2 protein were greater in the cytosolic than in the microsomal fraction (P < 0.01). Oxytocin did not affect the amount of cPLA2 protein in either fraction (P > 0.10). In conclusion, oxytocin did not effect expression of either cPLA2 mRNA or protein in ovine endometrium. Oxytocin may stimulate PGF2alpha synthesis by activating cPLA2 protein that is already present in an inactive form.

Luteolysis: a neuroendocrine-mediated event

In many nonprimate mammalian species, cyclical regression of the corpus luteum (luteolysis) is caused by the episodic pulsatile secretion of uterine PGF2alpha, which acts either locally on the corpus luteum by a countercurrent mechanism or, in some species, via the systemic circulation. Hysterectomy in these nonprimate species causes maintenance of the corpora lutea, whereas in primates, removal of the uterus does not influence the cyclical regression of the corpus luteum. In several nonprimate species, the episodic pattern of uterine PGF2alpha secretion appears to be controlled indirectly by the ovarian steroid hormones estradiol-17beta and progesterone. It is proposed that, toward the end of the luteal phase, loss of progesterone action occurs both centrally in the hypothalamus and in the uterus due to the catalytic reduction (downregulation) of progesterone receptors by progesterone. Loss of progesterone action may permit the return of estrogen action, both centrally in the hypothalamus and peripherally in the uterus. Return of central estrogen action appears to cause the hypothalamic oxytocin pulse generator to alter its frequency and produce a series of intermittent episodes of oxytocin secretion. In the uterus, returning estrogen action concomitantly upregulates endometrial oxytocin receptors. The interaction of neurohypophysial oxytocin with oxytocin receptors in the endometrium evokes the secretion of luteolytic pulses of uterine PGF2alpha. Thus the uterus can be regarded as a transducer that converts intermittent neural signals from the hypothalamus, in the form of episodic oxytocin secretion, into luteolytic pulses of uterine PGF2alpha. In ruminants, portions of a finite store of luteal oxytocin are released synchronously by uterine PGF2alpha pulses. Luteal oxytocin in ruminants may thus serve to amplify neural oxytocin signals that are transduced by the uterus into pulses of PGF2alpha. Whether such amplification of episodic PGF2alpha pulses by luteal oxytocin is a necessary requirement for luteolysis in ruminants remains to be determined. Recently, oxytocin has been reported to be produced by the endometrium and myometrium of the sow, mare, and rat. It is possible that uterine production of oxytocin may act as a supplemental source of oxytocin during luteolysis in these species. In primates, oxytocin and its receptor and PGF2alpha and its receptor have been identified in the corpus luteum and/or ovary. Therefore, it is possible that oxytocin signals of ovarian and/or neural origin may be transduced locally at the ovarian level, thus explaining why luteolysis and ovarian cyclicity can proceed in the absence of the uterus in primates. However, it remains to be established whether the intraovarian process of luteolysis is mediated by arachidonic acid and/or its metabolite PGF2alpha and whether the central oxytocin pulse generator identified in nonprimate species plays a mediatory role during luteolysis in primates. Regardless of the mechanism, intraovarian luteolysis in primates (progesterone withdrawal) appears to be the primary stimulus for the subsequent production of endometrial prostaglandins associated with menstruation. In contrast, luteolysis in nonprimate species appears to depend on the prior production of endometrial prostaglandins. In primates, uterine prostaglandin production may reflect a vestigial mechanism that has been retained during evolution from an earlier dependence on uterine prostaglandin production for luteolysis.

Hormone replacement therapy and urinary prostaglandins in postmenopausal women

The objective of the study was to observe the effects of hormone replacement therapy upon urinary prostaglandin E2 and prostaglandin F2 alpha levels in postmenopausal patients. A total number of 55 women were enrolled in this study and 15 premenopausal (PreM) healthy subjects constitute the control group. A total of 40 patients at least 12 months after their natural menopause were divided into two groups: 15 of them was not medicated hormone replacement therapy (which composed NRHRT group) while 25 of the rest, received conjugated estrogen (Premarin) 0.625 mg/day orally plus medroxyprogesterone acetate (Farlutal) 10 mg/day orally built up the RHRT group. PGE2 and PGF2 alpha levels were measured with PGE2 [125I] and PGF2 alpha [3H] RIA kits. Statistical significance was analyzed by Student's t-test for impaired data. NRHRT and RHRT patients had had increased urinary PGE2 levels when compared with PreM (P < 0.001). HRT caused a significant decrease in PGE2 levels in menopausal women (P < 0.001). Urinary PGF2 alpha values of NRHRT and RHRT were significantly lower (P < 0.001) in comparison with PreM group. There was no difference in PGF2 alpha values between two postmenopausal groups. HRT given to postmenopausal patients might have a positive impact on prostaglandins and therefore on bone turnover in a series of various mechanisms.

Evidence that the conceptus contributes to the inhibition of follicular growth in the ewe

The present study was designed to determine the contribution of the gravid uterus and the conceptus in the inhibition of antral follicular growth. All antral follicles were counted and measured on day 48 post mating in ovaries of pregnant ewes (Group 1, n = 5) and in ovaries of ewes from which the uterus (Group 2, n = 5) or the conceptus (Group 3, n = 5) had been surgically removed on days 32-33 post mating. The secretory activity of the corpora lutea was maintained after removal of the uterus or the conceptus until slaughter of ewes. No difference was found between the three groups of ewes in the mean (+/-SEM) total number (non-atretic and atretic) of follicles per ewe, being 59.8 +/- 7.6, 35.0 +/- 7.6 and 50.8 +/- 4.6, respectively for Groups 1, 2 and 3. The mean (+/-SEM) number of follicles 2 mm or more in diameter was greater (P < 0.01) in Group 2 ewes (3.4 +/- 0.5) and Group 3 ewes (4.2 +/- 0.5) than in Group 1 ewes (1.6 +/- 0.4). Of all follicles counted which were 2 mm or larger, 90% in Group 1 were atretic, this value being higher (P < 0.05) than in Group 2 (68%) and Group 3 (55%). The mean (+/-SEM) diameter of the largest (F1) and second largest (F2) follicles was greater (P < 0.01) in Group 2 (F1, 4.0 +/- 0.4; F2, 3.2 +/- 0.4) and in Group 3 (F1, 3.9 +/- 0.2; F2, 3.3 +/- 0.2) than in Group 1 (F1, 2.6 +/- 0.1; F2, 2.2 +/- 0.1). The mean diameter (+/-SEM) of the largest non-atretic follicles was greater (P < 0.01) in Group 2 (4.0 +/- 0.4) and Group 3 (3.9 +/- 0.2) than in Group 1 (1.7 +/- 0.3). In conclusion, the results from this in vivo experiment provide evidence that the conceptus prevents the development of large healthy follicles by inducing atresia during the first trimester of pregnancy. The inhibition of follicular growth would reduce oestradiol production and permit the maintenance of luteal function during early pregnancy.

Prostaglandin F2 alpha and E2 production into uterine lymph of pregnant and non-pregnant ewes

Uterine lymphatic cannulation was performed in pregnant and non-pregnant ewes so that serial lymph samples could be analysed for prostaglandins (PGs) on day 12 to 18 after oestrus. The production of PGF2 alpha into uterine lymph showed peaks of > 1000 pg/h between days 14 and 18 of the oestrous cycle. Such peaks were either absent or much reduced (< 900 pg/h) over the same period in four pregnant animals. PGE2 production into uterine lymph remained low (< 510 pg/h) both in the four non-pregnant animals in the later part of the oestrous cycle and in three of four pregnant animals between days 14 to 18 post mating.

Influence of progesterone levels on prostaglandin concentrations in isolated uterine tissue and incubation medium from pseudopregnant rats

We measured the synthesis and secretion of uterine prostaglandins E and F2 alpha (PGE and PGF2 alpha) by the uterus in vitro from pseudopregnant (psp) rats on days 5 and 10 of psp, when level of serum progesterone was high and low, respectively. We found a direct correlation between concentration of progesterone in serum and uterine content of PGE and an inverse correlation with uterine PGF2 alpha. On day 5, when progesterone was high in serum, PGE increased in tissue more than in the incubation medium, suggesting a poor liberation of this PG or utilization of PGE by the tissue. On this day, no difference was seen between content of uterine PGF2 alpha and PGF2 alpha in the incubation medium. Nevertheless, on day 10, when progesterone was lower, concentrations of both PGE and PGF2 alpha were greater (P < 0.001) in the medium than in the uterine tissue. However, PGF2 alpha in the medium was higher than PGE (P < 0.05). The results clearly demonstrate that the synthesis and release of PGE and PGF2 alpha were modified by the concentration of progesterone in the serum.

The control of prostaglandin production by the endometrium in relation to luteolysis and menstruation

Oestradiol acting on a progesterone-primed uterus stimulates prostaglandin (PG) F2 alpha synthesis by the endometrium. In some species (notably the sheep, cow and goat) oxytocin released from the ovary also forms part of the physiological stimulus for increased endometrial PGF2 alpha production. The corpus luteum contains high concentrations (> 1 microgram/g tissue) of this peptide in these species. The intracellular mechanisms by which these three hormones control endometrial PGF2 alpha synthesis and release are far from clear. Oxytocin stimulates the synthesis of inositol phosphates and diacylglycerol in the endometrium of some species, but whether this pathway is involved in endometrial PGF2 alpha synthesis is still open to question. There is evidence that increased endometrial PGF2 alpha synthesis is dependent upon increased endometrial protein synthesis but, apart from the recorded effects of steroid hormones on the concentrations of phospholipase A2, prostaglandin H synthase and oxytocin receptors, it is not known what other endometrial proteins are involved. Some disorders of menstruation are associated with abnormal PG production by the endometrium, but the reasons for this abnormality are not clear. During early pregnancy an increase in PGF2 alpha synthesis by the endometrium is prevented, except in the pig where the PGF2 alpha produced is directed from the venous drainage to the uterine lumen. In those species in which endometrial PGF2 alpha synthesis is dependent upon oxytocin secreted by the ovary, the conceptus secretes an interferon-tau (previously named trophoblast protein-1) which prevents oestradiol and oxytocin acting on a progesterone-primed uterus from stimulating endometrial PGF2 alpha synthesis. The identities of the factors produced by the conceptus which prevent endometrial PGF2 alpha synthesis during early pregnancy in other species are not known, although it is clear that they are not interferons.

The role of the endometrial oxytocin receptor in determining the length of the sterile oestrous cycle and ensuring maintenance of luteal function in early pregnancy in ruminants

The oxytocin receptor, a seven transmembrane domain, G protein-linked receptor molecule, plays a central role in determining the endocrine function of the ruminant uterine endometrium. During nonpregnant cycles the control of this molecule by circulating steroid hormones leads to regression of the corpora lutea. The kinetics of the mechanisms involved determine the time at which luteolysis occurs, and therefore the length of the oestrous cycle. In pregnancy, secretions of the trophoblast block endometrial oxytocin receptor gene expression and lead to luteal maintenance. An understanding of the molecular mechanisms involved in the steroidal control of oxytocin receptor gene expression will provide an explanation for the relative constancy of oestrous cycle lengths in non-pregnant animals. Unravelling the way in which trophoblast products block expression of the oxytocin receptor gene will lead to a better understanding of the reasons for the high rate of embryonic loss in domestic ruminants.

Effects of estrogen treatment and inhibition of prostanoid synthesis on myometrial activity and gap junction formation in the oophorectomized ewe

The objective was to elucidate the functional relationship between estradiol-induced changes in myometrial activity, uterine prostanoid synthesis, and gap junction formation in vivo. The study design was as follows. The effects of inhibition of prostanoid synthesis with naproxen on formation of gap junctions and coordination of electrical and mechanical myometrial activity induced by estradiol-17 beta were investigated in 6 chronically instrumented oophorectomized ewes. Prostanoid metabolites were measured in arterial and uterine venous plasma. Myometrial biopsies were obtained to determine gap junction area. The results were that intraarterial administration of 0.1 mg of estradiol-17 beta was followed by a significant increase in maximum rate of rise of the intrauterine pressure cycles and a significant decrease in conduction time of bursts of electrical activity; this response was not altered by pharmacologic inhibition of uterine prostanoid synthesis using naproxen. Estradiol administration during continuous naproxen infusion increased gap junction area. The conclusion is that improved coordination of myometrial activity and formation of myometrial gap junctions induced by estradiol is not mediated by prostaglandins.

Phospholipase A2 activity in endometrium from early pregnant and non-pregnant ewes

In the ewe, synthesis of the luteolytic factor, prostaglandin F2 alpha, increases from day 13 to the end of the estrous cycle. Availability of free arachidonic acid is usually the rate-limiting step in prostaglandin biosynthesis. Phospholipase A2 (PLA2) may be the key enzyme for the hydrolysis of arachidonic acid from membrane-bound phospholipids. To investigate uterine PLA2 activity during the estrous cycle and early pregnancy, we monitored the release of [14C]oleic acid from the substrate 1-palmitoyl-2-[14C]oleoyl-phosphorylcholine by homogenates and cytosolic fractions of endometrium from ewes on days 12, 14 and 16 of the estrous cycle or pregnancy. We observed that PLA2 activity dropped by 58% (p < 0.02) in day-16 pregnant endometrium compared to day-16 non-pregnant endometrium. We then investigated whether the reduced PLA2 activity was due to induction of a specific inhibitor. The PLA2-inhibitor activity was determined by monitoring the inhibition of release of [14C]oleic acid from the radioactive substrate by porcine pancreatic PLA2. Inhibition by endometrial homogenates of pregnant animals of the control enzyme activity was 27% and only 14% by cyclic ones. Inhibition was dose-dependent and was as high as 53% (p < 0.01) with 1 mg protein from pregnant endometrial homogenates. Endometrial PLA2 behaved as a Michaëlian enzyme in the endometrium of day-16 cyclic ewes (Km = 79.4 mumol/l). Furthermore, the inhibitory activity from pregnant endometrium had characteristics of competitive inhibition. Our results suggest that inhibition of endometrial PLA2 activity could occur in early pregnant ewes.

Is there cross-refractoriness between phospholipase A2 and the calcium ionophore A23187 in the stimulation of uterine prostaglandin production?

Phospholipase (PL) A2 increased the outputs of prostaglandin (PG) F2 alpha, PGE2 and 6-keto-PGF1 alpha from the mid-cycle guinea-pig uterus, but repeating the PLA2 treatment 1 h later failed to increase uterine PG output. Similarly, A23187 increased PG output from the mid-cycle guinea-pig uterus, but repeating the A23187 treatment 1 h later produced a very much smaller stimulatory effect. Thus the guinea-pig uterus showed complete refractoriness to PLA2 and partial refractoriness to A23187, as regards the stimulation of uterine PG production, when the uterus is treated with the same compound after an interval of 1 h. However, when the mid-cycle guinea-pig uterus was treated with PLA2 1 h after being treated with A23187, or was treated with A23187 1 h after being treated with PLA2, the second compound produced a normal stimulation of PG output and was not affected, therefore, by treatment with the first compound. Consequently, there is no cross-refractoriness between PLA2 and A23187 as regards their stimulatory effects on PG production by the guinea-pig uterus.

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 vivo desensitization of a high affinity PGF2 alpha receptor in the ovine corpus luteum

The corpus luteum (CL) of the sheep exhibits a differential sensitivity to PGF2 alpha in vivo in terms of an increase in oxytocin (OT) secretion and a decrease in progesterone secretion, pointing to the presence in vivo of both high and low affinity receptors for PGF2 alpha. The presence of the high affinity PGF2 alpha receptor was assessed by monitoring the secretion rate of OT from the ovine CL in response to subluteolytic infusions of PGF2 alpha. Rapid desensitization to PGF2 alpha occurred after only one hour of infusion, while a minimum rest period of six hours was required to restore sensitivity. The possibility that these findings could be explained by the depletion and resynthesis of OT was excluded by demonstrating an increase in OT secretion rate with supra-physiological levels of PGF2 alpha two hours after desensitization. Collectively, these results indicate the presence of a high affinity receptor for PGF2 alpha in the ovine CL which exhibits desensitization and recovery in vivo. The temporal nature of the desensitization and recovery of the high affinity PGF2 alpha receptor controlling luteal OT secretion may contribute to the pulsatile nature of PGF2 alpha release from the ovine uterus.

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.

Chronic utero-ovarian vein catheterization with subsequent occlusion prolongs the estrous cycle and changes electromyographic activity in the myometrium of ewes

The objective of our study was to determine the effect of chronic utero-ovarian vein catheterization in ewes on estrous cycle length, plasma progesterone (P) concentration, and myometrial electromyographic activity. Cyclic ewes with inferior vena cava catheters were used as controls. Estrus was synchronized in ten ewes and 10 to 12 d following estrus, the ewes were anesthetized, fitted with myometrial electromyograph leads and with utero-ovarian vein (n = 5) or inferior vena cava (n = 5) catheters. After surgery, ewes returned to estrus as expected (16 to 18 d interestrus interval). The second cycle of four of five ewes with utero-ovarian vein catheters were prolonged (40 to 58 d). The inferior vena cava catheterized ewes had normal length second cycles. Plasma P concentrations reflected the estrous cycles: low (</= 0.01 ng/ml) at estrus and 2 to 3 ng/ml at midcycle. The inferior vena cava catheterized ewes had decreased plasma P concentrations after luteolysis (Days 13 to 14) while four of five utero-ovarian vein catheterized ewes maintained elevated plasma P concentrations for 20 to 58 d. Catheterization affected the myometrial electromyograph; short events (16 to 180 sec) were increased on Days 5 to 13 in utero-ovarian vein as compared with inferior vena cava catheterized ewes (P < 0.05); long events (180 to 900 sec) tended to decrease from Days 1 to 15 in utero-ovarian vein ewes, but this was not statistically significant (P > 0.05).

Prostaglandin F2 alpha, oxytocin and progesterone secretion by bovine luteal cells at several stages of luteal development: effects of oxytocin, luteinizing hormone, prostaglandin F2 alpha and estradiol-17 beta

Bovine luteal cells from Days 4, 8, 14 and 18 of the estrous cycle were incubated for 2 h (1 x 10(5) cells/ml) in serum-free media with one or a combination of treatments [control (no hormone), prostaglandin F2 alpha (PGF), oxytocin (OT), estradiol-17 beta (E) or luteinizing hormone (LH)]. Luteal cell conditioned media were then assayed by RIA for progesterone (P), PGF, and OT. Basal secretion of PGF on Days 4, 8, 14 and 18 was 173.8 +/- 66.2, 111.1 +/- 37.8, 57.7 +/- 15.4 and 124.3 +/- 29.9 pg/ml, respectively. Basal release of OT and P was greater on Day 4 (P less than 0.01) than on Day 8, 14 and 18 (OT: 17.5 +/- 2.6 versus 5.6 +/- 0.7, 6.0 +/- 1.4 and 3.1 +/- 0.4 pg/ml; P: 138.9 +/- 19.5 versus 23.2 +/- 7.5, 35.4 +/- 6.5 and 43.6 +/- 8.1 ng/ml, respectively). Oxytocin increased (P less than 0.01) PGF release by luteal cells compared with control cultures irrespective of day of estrous cycle. Estradiol-17 beta stimulated (P less than 0.05) PGF secretion on Days 8, 14 and 18, and LH increased (P less than 0.01) PGF production only on Day 14. Prostaglandin F2 alpha, E and LH had no effect on OT release by luteal cells from any day. Luteinizing hormone alone or in combination with PGF, OT or E increased (P less than 0.01) P secretion by cells from Days 8, 14 and 18. However on Day 8, a combination of PGF + OT and PGF + E decreased (P less than 0.05) LH-stimulated P secretion. These data demonstrate that OT stimulates PGF secretion by bovine luteal cells in vitro. In addition, LH and E also stimulate PGF release but effects may vary with stage of estrous cycle.

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.

Plasma prolactin concentrations in mares and their neonates after oxytocin induction of parturition

Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and 11.9 ng/ml respectively; P less than 0.1). The average concentration of prolactin over the last 4 days (Days -3 to 0) had increased by 40% when compared to the average concentration on Days -6, -5, and -4. These findings indicate a rising trend which appears to occur concomitantly with changes in concentrations of 2 mammary components tested, sodium and potassium. Prolactin concentrations did not significantly increase in term mares after oxytocin treatment or in spontaneously foaling mares. However, the preterm induced mares had higher prolactin concentrations during the first stage of labor (19.3 +/- 7.2 ng/ml) than prior to treatment with oxytocin (4.7 +/- 2.0 ng/ml; P less than 0.01). Levels of prolactin in all groups significantly declined by 20-min post-placental expulsion. For the first 30 min after birth, prolactin concentrations in foals from oxytocin-induced mares appeared to be 2-fold higher than those from spontaneously foaling mares. Thereafter, prolactin values declined to baseline values by 48 hrs. When comparing cord arterial plasma with cord venous plasma in each group, prolactin concentrations were similar. However, the average prolactin levels in both the cord artery and vein appeared higher (ave: 1.1 ng/ml) in Group II and III than in Group I (less than 0.5 ng/ml). From these results, the authors suggest that 1) prolactin may have a role in regulating mammary secretory products in mares just prior to parturition; 2) oxytocin may increase prolactin secretion in preterm induced mares; 3) oxytocin induction may have a short term effect to increase circulatory prolactin concentrations in neonates in utero regardless whether their dams were treated preterm or term.

The effect of estradiol-17 beta and actinomycin D on the release of PGF and PGE from separated cells of human endometrium

Estradiol-17 beta selectively stimulated the release of PGF from separated glandular but not stromal cells of human secretory endometrium (p less than 0.025) but had no effect on PGF release from either type of cells obtained from proliferative endometrium. PGE release was not affected by estradiol-17 beta. Actinomycin D did not antagonise the effect of estradiol-17 beta on PGF release from secretory, glandular cells. Basal release of PGF from these cells was stimulated by actinomycin D alone (100 ng/ml) (p less than 0.025) and PGE release stimulated in the presence of estradiol-17 beta. Actinomycin D had no effect on PGF or PGE release from proliferative endometrium. These findings suggest that estradiol-17 beta stimulates PGF release by a mechanism that does not affect PGE release and which is not dependent on the synthesis of new protein. The basal release of PGF and PGE by glandular cells of secretory endometrium in vitro is regulated by protein/proteins which reduce PG release.

Effects of progesterone withdrawal on uterine prostaglandin levels in the ovariectomized pregnant rat

Prostaglandin (PG) levels increase dramatically just before parturition in the rat. Coincident with this dramatic increase in uterine PGs is a precipitous decrease in plasma progesterone and enhanced plasma estradiol levels. The purpose of the present study was to mimic the progesterone withdrawal phenomenon in the presence and absence of estradiol in ovariectomized pregnant rats and determine the effects on uterine PGF, PGE, thromboxane B2 (TxB2) and 6-keto-PGF1a (6KF) levels. Rats were ovariectomized on day 16 of pregnancy and silastic inserts containing progesterone and estradiol placed s.c. in two groups of rats (I and II) while the third group (III) received progesterone only. On day 19 of pregnancy progesterone was withdrawn from groups II and III and rats sacrificed 0, 6, 12 and 24 hours later. Uterine tissue was assayed for PGs by radioimmunoassay. Progesterone withdrawal in the absence of estradiol (III) administration significantly (p less than .05) elevated PGE, TxB2 and 6KF, but not PGF, at the 24 hour period compared to controls (I). When progesterone was withdrawn in the presence of exogenously administered estradiol (II) only PGF showed enhancement (p less than .05) over III at the 24 hour period thus indicating a specific effect of estradiol on the PGF metabolic pathway. In conclusion, these data indicate that: (1) progesterone withdrawal is a potent stimulus for uterine PG production and is probably a major contributor to the augmented uterine PGE, TxB2 and 6KF levels at term in the pregnant rat; and (2) progesterone withdrawal in the presence of exogenously administered estradiol enhances uterine PGF production thus indicating a specific effect of estradiol on PGF production.

Uterine motility in the cow during the estrous cycle. III. Effects of oxytocin, xylazine, and adrenoceptor blockers

Intrauterine pressure (IUP) was recorded in nonlactating dairy cows using an intraluminal catheter with two micropressure transducers located 15 cm apart at the distal end. There was a significant increase (P < 0.05) in IUP following administration of xylazine and oxytocin at all four stages of the estrous cycle. The most significant increase in IUP occurred during proestrus for both drugs. The effect of pretreatment with adrenoceptor-blocking agents on IUP changes induced by xylazine and oxytoxin was evaluated. Alpha-1 adrenoceptor blockade (prazosin) had no effect on IUP following xylazine treatment. However, alpha-2 adrenoceptor blockade (yohimbine) resulted in a reduction (P < 0.05) in IUP compared to controls. Neither prazosin or yohimbine affected oxytocin-induced IUP.

Uterine motility in the cow during the estrous cycle. II. Comparative effects of prostaglandins F2α, E2, and cloprostenol

Intrauterine pressure (IUP) changes were recorded in nonlactating, cyclic dairy cows using transcervically placed intraluminal pressure microtransducers. Spontaneous activity was recorded for the first 30 min. Prostaglandins (PG) F(2alpha) (5 mug/kg), E(2) (5 mug/kg), or cloprostenol (0.1 mug/kg) were then injected intravenously (i.v.) at diestrus, proestrus, estrus, and metestrus, and their effects were recorded. The drug administrations did not alter the duration of the estrous cycle of the cows. Single doses of PGF(2alpha) and E(2) significantly increased uterine activity at all stages of the estrous cycle, while cloprostenol had no effect. PGF(2alpha) and PGE(2) increased IUP, frequency, and amplitude during all stages of the estrous cycle. The spontaneous pattern resumed within 20 min postinjection. Partial uterine refractoriness occurred with both PGs. The results indicate that low doses of natural prostaglandins stimulate uterine activity during the estrous cycle in cattle.

Concentrations of uterine luminal prostaglandins in mares with acute and persistent endometritis

Intrauterine infusion of 1 per cent oyster glycogen solution was used to induce acute endometritis in four genitally normal mares. Numbers of viable neutrophils recovered in uterine washings had increased by 1 h after infusion and remained elevated for at least 72 h. There was a significant correlation between numbers of viable neutrophils and total protein concentrations and between prostaglandin (PG)F and PGE2 concentrations in washings. There was also a significant relationship between concentrations of 15-keto-13, 14-dihydro PGF2 alpha in plasma and PGF in washings. Intrauterine concentrations of PGF were influenced by cycle stage and in turn the induced acute endometritis interfered with normal ovarian function. Mares with persistent endometritis had significantly higher concentrations of PGF and total protein and percentage of neutrophils and mononuclear cells in washings than normal mares. White blood cells from mares were capable of producing PGF and PGE2 in vitro.

Uterine prostaglandin and blood flow responses to estradiol-17 beta in cyclic cattle

Normal cyclic dairy cattle (n = 7) underwent a midventral laparotomy on day 17 of the estrous cycle and were fitted, ipsilateral to the CL, with: an electromagnetic flow transducer around the uterine artery (UA; n = 5); catheters within the ovarian vein (OV; n = 7) via a uterine branch of the ovarian vein, uterine branch of the ovarian artery (UBOA; n = 5) and facial artery (FA; n = 7). On day 18, blood samples were collected at 30 min intervals for 1 h prior to injection of estradiol-17 beta (E2; 3 mg) and 12 h post-E2. Uterine blood flow (UBF) was monitored continuously and plasma samples analyzed for PGF2 alpha and PGFM. Exact locations of catheters in reproductive tracts were verified post-slaughter. Data were analyzed by method of least squares analysis of variance. Uterine blood flow (ml/min) increased above pre-E2 flow rates within 30 min post-E2 injection, peaked between 2.5 to 3.5 h and declined between 4 to 8.5 h. A small secondary rise in UBF occurred between 9 and 12 h. Regression analysis for concentrations (pg/ml) of PGF2 alpha and PGFM in the OV (i.e., [OV]-[FA]) demonstrate a similar response as PGFM concentration in the FA in that all increased at approximately 3 h, peaked between 5 and 7 h and returned to near baseline levels by 9 to 10 h post-E2. Facial artery PGFM concentrations were positively correlated with uterine production of PGF2 alpha (r = .66) and PGFM (r = .30), whereas FA PGF2 alpha concentrations were not. In three of five cows, a difference in PGF2 alpha was detected between UBOA and FA (UBOA greater than FA); supportive of a local countercurrent exchange between the uterine venous drainage and the ovarian artery.

Role of progesterone in regulating uteroovarian venous concentrations of PGF2 alpha and PGE2 during the estrous cycle and early pregnancy in ewes

The role of progesterone in regulation of uteroovarian venous concentrations of prostaglandins F2 alpha(PGF2 alpha) and E2 (PGE2) during days 13 to 16 of the ovine estrous cycle or early pregnancy was examined. At estrus, ewes were either mated to a fertile ram or unmated. On day 12 postestrus, ewes were laparotomized and a catheter was inserted into a uteroovarian vein. Six mated and 7 unmated ewes received no further treatment. Fifteen mated and 13 unmated ewes were ovariectomized on day 12 and of these, 7 mated and 5 unmated ewes were given 10 mg progesterone sc and an intravaginal pessary containing 30 mg of progesterone. Uteroovarian venous samples were collected every 15 min for 3 h on days 13 to 16 postestrus. Mating resulted in higher mean daily concentrations of PGE2 in the uteroovarian vein than in unmated ewes. Ovariectomy prevented the rise in PGE2 with day in mated ewes but had no effect in unmated ewes. Progesterone treatment restored PGE2 in ovariectomized, mated ewes with intact embryos. Mating had no effect on mean daily concentrations of PGE2 alpha or the patterns of the natural logarithm (1n) of the variance of PGF2 alpha. Ovariectomy resulted in higher mean concentrations and 1n variances of PGF2 alpha on day 13 and lower mean concentrations and 1n variances of PGF2 alpha on days 15 and 16. Replacement with progesterone prevented these changes in patterns of mean concentrations and 1n variances of PGF2 alpha following ovariectomy. It is concluded that progesterone regulates the release of PGF2 alpha from the uterus, maintaining high concentrations while also preventing the occurrence of the final peaks of PGF2 alpha which are seen with falling concentrations of progesterone. This occurs in both pregnant and non-pregnant ewes. Progesterone is also needed to maintain increasing concentrations of PGE2 in mated ewes.

Sex steroid hormone concentrations in preterm labour and the outcome of treatment with ritodrine

Peripheral plasma concentrations of unconjugated oestradiol-17 beta, progesterone and total oestriol were measured in patients presenting with uncomplicated preterm labour. Control samples were obtained from normal healthy women matched for maternal age, parity and duration of pregnancy. Oestrogen concentrations were often higher and progesterone concentrations often lower in patients presenting in preterm labour, and in particular, in those presenting in advanced labour and those failing to respond to treatment with ritodrine, but the differences were not statistically significant.

Prostaglandin F and E levels in the conceptus, uterus and plasma during early pregnancy in the ewe

Concentrations of prostaglandins E and F (PGE and PGF) were measured in the embryo or fetus, extra embryonic or fetal membranes (membranes), intercaruncular and caruncular endometrium and plasma collected from uterine and ovarian arterial and venous vessels from separate groups of ewes laparotomized at 5 day intervals from day 10 to day 55 of pregnancy. Our purpose was to investigate the role of prostaglandins E and F in the maternal recognition of pregnancy, implantation and early placental function. Our data suggest that the initial maintenance of the corpus luteum in the pregnant ewe does not involve a reduction in PGF production, compared to pregnant ewes; but a change in the pattern of PGF secretion. This is accompanied by an elevation in PGE production of similar magnitude to that observed in non pregnant ewes. The extra embryonic/fetal membranes appear to be the major source of elevated PGF levels in the maternal circulation prior to day 30 of pregnancy. Between days 35 and 55 of gestation the rising PGF levels in maternal serum probably come from the fetus. Over the same period PGE levels rise in the fetus and intercaruncular endometrium, but PGE secretion into the maternal circulation is not enhanced. A role for PGF and PGE in fetal, placental and uterine growth is suggested; placental and uterine endocrine function may also be targets.

Contribution to the pathogenesis of dysmenorrhea

Menstrual blood was collected from five eumenorrheic and seven dysmenorrheic women aged between 20 and 35 years for a period of three cycles each. The levels of prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha)-the stable metabolite of prostacyclin (PGI2)-, oestradiol, oestrone, and progesterone were determined radioimmunologically. Both eumenorrheic and dysmenorrheic women showed identical blood losses. The levels of oestradiol excreted by the dysmenorrheic women were markedly elevated as compared to the non-dysmenorrheic subjects (2 p less than 0.05). Oestrone excretion was in the same order of magnitude in all subjects examined. The concentration of progesterone per menstruation was significantly higher in the eumenorrheic women (2 p less than 0.02) than in the dysmenorrheic patients. Menstrual excretion of PGF2 alpha was 2.5 times higher in the dysmenorrheic women compared to the normal subjects (2 p less than 0.05). The levels of PGE2 was identical in both groups. Excretion of 6-k-PGF1 alpha was significantly lower in the dysmenorrheic women than in the eumenorrheic subjects (2 p less than 0.02). The oestradiol/progesterone ratio showed a distinct predominance of oestradiol in the dysmenorrheic patients. PGF2 alpha dominance in the dysmenorrheic patients is expressed by the PGF2 alpha/6-k-PGF1 alpha and the PGF2 alpha/PGE2 ratios. A shift in the oestradiol/progesterone ratio in favour of oestradiol seems to be the underlying pathogenic principle of dysmenorrhea. The oestradiol dominance is associated with a shift in the PGF2 alpha/PGI2 and the PGF2 alpha/PGE2 proportions. Thus, the PGF2 alpha predominance and a simultaneous reduction of PGI2 in uterine tissue seem to be responsible for dysmenorrheic bleeding.

Temporal response of uterine prostaglandins to estradiol treatment in the ovariectomized-pregnant 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) levels but had no effect on 6-Keto-PGF1 alpha (6KF) concentrations in ovariectomized-pregnant rats. One explanation for the lack of an augmentation in 6KF was a temporal difference 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 greater than .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 less than .05) increases (2.4, 3.4 and 2.1 fold, respectively) compared to 12 hours. In contrast, no significant augmentation in 6KF levels (p greater than .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 greater than .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.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis of prostaglandin F by cultured human endometrial cells

Human endometrial cells were dispersed with collagenase and maintained in culture overnight. The synthesis of PGF by the dispersed cells incubated at 37 degrees C in serum-free medium was stimulated by estradiol (10(-7)M - 10(-5)M), histamine (5X10(-7)M - 5X10(-5)M), bradykinin (10(-6)M), phorbol myristate (PMA, 3X10(-8)M) and arachidonate (5X10(-6)M). Preincubation of the cells for 3 h with cortisol (5X10(-7)M - 5X10(-5)M), progesterone (10(-6)M) or mepacrine (10(-6)M - 2X10(-4)M) inhibited the response to histamine, bradykinin and PMA but not to arachidonate. Perfusion of the cultured cells in filtration chambers yielded similar results to those obtained in the incubation system but differences in the onset and duration of the responses to stimuli were found. In the perifusion system the responses to histamine and bradykinin were rapid and of short duration (peak response in less than 60 min) while the responses to PMA and arachidonate were of longer duration with a slower onset. We conclude that these observations using dispersed endometrial cells are consistent with previous work showing that histamine, bradykinin and PMA act by stimulating acylhydrolase activity, thereby liberating precursors such as arachidonic acid which are converted to prostaglandins by the cyclo-oxygenase complex.

Effects of 17 beta-estradiol and progesterone on the levels of prostaglandins F2 alpha and E in human endometrium

17 beta-estradiol and progesterone were administered to post-menopausal women to determine their effects in vivo on the capacity of human endometrium to synthesize prostaglandins (PGs) F2 alpha and E. Basal amounts of PGF2 alpha and PGE synthesized by endometrium exposed to 17 beta-estradiol and progesterone were significantly higher than the levels produced by endometrium exposed to 17 beta-estradiol alone (p less than 0.02 for both PGs). Levels found in the former endometrium were broadly comparable to levels in secretory endometrium and in the latter to amounts found in proliferative endometrium of spontaneous, ovulatory cycles.