PGF2 Alpha Synthesis Research Articles

Luteal peptides and intercellular communication

The variety of peptides synthesized by the corpus luteum (relaxin, vasopressin, oxytocin and oxytocin-related neurophysin) and their possible intracellular effects are reviewed. After luteinization of the granulosa cells and in response to LH and FSH, the output of oxytocin is increased. In addition, insulin-like growth factor is a very potent stimulus of oxytocin secretion. Although luteal cells respond to gonadotrophins by increased production of progesterone, there is no further secretion of oxytocin. Oxytocin is localized in large luteal cells which seem not to be under the direct control of gonadotrophins. Synthesis of luteal oxytocin seems to occur during the early luteal phase according to measurements of oxytocin mRNA. Highest tissue concentrations and secretion under in-vitro conditions were observed during the mid-luteal phase, and so synthesis, storage and secretion are unlikely to occur concomitantly. Under in-vitro conditions, oxytocin is secreted concomitantly with neurophysin and progesterone, and there appears to be some form of communication between small and large luteal cells for the secretion of progesterone and oxytocin under in-vivo conditions. Evidence has been obtained that oxytocin may have local effects in the ovary by inhibition of secretion (synthesis ?) of progesterone, especially during the early luteal phase. A mechanism can be suggested whereby, under physiological conditions, oxytocin may delay the increase of progesterone by inhibition of progesterone secretion and therefore delay down regulation of its own receptor. This would prolong the life-span of the CL and the oestrous cycle. Exogenous progesterone given on Days 1-4 shortens the cycle to about 12 days. The best evidence that oxytocin may be involved in controlling luteolysis comes from immunization experiments in ewes and goats, but there is no clear evidence of this type for cattle. Basal concentrations of oxytocin at the end of the luteal phase may interact with oxytocin receptors after the inhibitory effect of progesterone in the uterus is reduced, thus initiating synthesis of PGF-2 alpha.

Physiological mechanisms of pregnancy recognition in ruminants

Maternal recognition of pregnancy in sheep, cattle and goats involves physiological mechanisms that result in protection of corpora lutea from luteolysis by modification or inhibition of uterine production of luteolytic pulses of prostaglandin (PG) F-2 alpha. Ovine, bovine and caprine luteal cells release oxytocin in a pulsatile manner during late dioestrus. Oxytocin then binds to its endometrial receptors and initiates luteolytic pulses of PGF-2 alpha. Ovine, bovine and caprine trophoblast protein-1 (oTP-1, bTP-1 and cTP-1) are secreted by the trophectoderm of conceptuses between Days 10 and 21-24 of pregnancy. These antiluteolytic proteins (oTP-1 and bTP-1) are primarily responsible for inhibiting uterine production of luteolytic amounts of PGF-2 alpha. During early pregnancy, the numbers of endometrial receptors for oxytocin are significantly lower in ewes and cows, and stimulatory effects of exogenous oxytocin on uterine production of PGF-2 alpha are correspondingly reduced or absent for ewes, cows and goats. Exogenous oestrogens can, through a uterine-dependent mechanism, stimulate synthesis of endometrial receptors for oxytocin and uterine production of PGF-2 alpha; an effect which is significantly attenuated during early pregnancy. These results suggest that oTP-1, bTP-1 and possibly cTP-1 exert their antiluteolytic effect(s) by: (1) inhibiting effects of oestrogen and/or progesterone necessary for synthesis of endometrial receptors for oxytocin; (2) inhibiting endometrial synthesis and/or recycling of oxytocin receptors directly; or (3) inducing the endometrium to synthesize an inhibitor of an enzyme(s) necessary for synthesis of PGF-2 alpha.

Significant improvement in cervical repair after surgery under the influence of specific anti-inflammatory therapy

The article describes the features of the management of patients with cervical dysplasia. After the surgical treatment of cervical neoplasia, patients experience abundant serous or serous bleeding from the genital tract, which leads to marked discomfort and secondary infection of the cervix. Secondary infection contributes to the prolongation of epithelialization of the cervix and the occurrence of a relapse of the disease.It emphasizes the importance of the prevention of postoperative symptoms that cause discomfort in women, secondary infection of the wound surface and prolongation of epithelialization of the cervix. These symptoms occur after trauma to the cervix due to an increase in prostaglandins, histamine and pro-inflammatory cytokines.The study showed that benzydamine hydrochloride reduces the abundance and duration of postoperative secretions from the wound surface by suppressing tissue edema and inhibiting the synthesis of proinflammatory cytokines – tumor necrosis factor and interleukin-1, which leads to increased reparative processes of the cervix epithelium. Benzydamine hydrochloride reduces capillary permeability, stabilizes lysosomal membranes, inhibits the production of adenosine triphosphate and other high-energy compounds in the processes of oxidative phosphorylation, inhibits the synthesis or inactivate prostaglandins, histamine, bradykinin, cytokines, complement factors and other endogenous non-specific “damaging factors”. It blocks the interaction of bradykinin with tissue receptors, restores impaired microcirculation and reduces pain sensitivity in the focus of inflammation, also affects the thalamic pain sensitivity centers (local blockade of PgE1, PgE2 and PgF2 alpha synthesis). The analgesic effect is due from indirect decrease in the concentration of biogenic amines, which have algenic properties, and an increase in the pain sensitivity threshold of the receptor apparatus.Thus, benzydamine hydrochloride Tantum Rosa® is the only non-steroidal anti-inflammatory agent for topical use in gynecology, which provides rapid epithelialization of the cervix and elimination of pathological secretions due to the specific inhibition of pro-inflammatory cytokines and activation of reparative processes in the epithelium.

Canine placental prostaglandin E2 synthase: expression, localization, and biological functions in providing substrates for prepartum PGF2alpha synthesis.

The prepartum output of PGF2alpha in the bitch is associated with increased placental PGE2-synthase (PTGES) mRNA levels. Contrasting with this is a decreased expression of PGF2alpha-synthase (PGFS/AKR1C3) in uteroplacental compartments during prepartum luteolysis, suggesting an involvement of alternative synthetic pathways in PGF2alpha synthesis, for example, conversion of PGE2 to PGF2alpha. However, because the expression and possible functions of the respective PTGES proteins remained unknown, no further conclusion could be drawn. Therefore, a canine-specific PTGES antibody was generated and used to investigate the expression, cellular localization, and biochemical activities of canine uteroplacental PTGES throughout pregnancy and at prepartum luteolysis. Additionally, the biochemical activities of these tissues involved in the conversion of PGE2 to PGF2alpha were investigated. The endometrial PTGES was localized in the uterine surface epithelium at preimplantation and in superficial and deep uterine glands, endothelial cells, and myometrium throughout pregnancy and at parturition. Placental signals were mostly in the trophoblast. The biochemical properties of recombinant PTGES protein were confirmed. Additionally, expression of two PGE2-receptors, PTGER2/EP2 and PTGER4/EP4, revealed their decreasing expression during luteolysis. In contrast, the uteroplacental expression of prostaglandin transporter (PGT) was strongly elevated prior to parturition. These localization patterns resembled that of PTGES. The increased expression of PTGES and PGT at parturition, together with the accompanying decreased levels of PGE2-receptors and the capability of canine uterine and placental homogenates to take part in the conversion of PGE2 to PGF2alpha, as found in this study, suggest that PGE2 could be used locally as a substrate for prepartum PGF2alpha synthesis in the dog.

Application of dietary fish oil in dairy cow reproduction

Feed fats are commonly used as a component of high-yielding cow diet rations. Many studies have been conducted on the effects of fat supplementation on metabolism, milk composition, and improvements in dairy cow reproduction. The positive effects on fat (vegetable oil) and energy supplementation on improvements in reproduction are well documented. Consumption of polyunsaturated fatty acids (PUFAs), including n-3 acids, in appropriate feed doses improves fertility of dairy cows. A fat source with high levels of acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is marine oil, especially fish and algae. By modification of cow rations, EPA and DHA can be utilized to reduce synthesis of PGF2 alpha in the endometrium, which can prevent luteolysis of the corpus luteum during early pregnancy. The PUFAs also may have a direct impact on key genes and their proteins that regulate biochemical processes and pathways between the corpus luteum, the uterus, and the embryo. The effect of n-3 fatty acids on the survival of embryos is not yet clearly defined.

Intraluteal Prostaglandin Biosynthesis and Signaling Are Selectively Directed Towards PGF2alpha During Luteolysis but Towards PGE2 During the Establishment of Pregnancy in Sheep1

In ruminants, endometrial prostalgandin (PG) F(2alpha) causes functional luteolysis, whereas luteal synthesis of PGF(2alpha) is required for structural luteolysis. PGE(2) is considered to be a luteoprotective mediator. Molecular aspects of luteal PGF(2alpha) and PGE(2) biosynthesis and signaling during the estrous cycle and establishment of pregnancy are largely unknown. The objectives of the present study were 1) to determine the regulation of proteins involved in PGF(2alpha) and PGE(2) biosynthesis, catabolism, transport and signaling in the corpus luteum (CL); 2) to investigate the transport of interferon tau (IFNT), PGF(2alpha), and PGE(2) from the uterus to the ovary through the vascular utero-ovarian plexus (UOP); and 3) to compare the intraluteal production of PGF(2alpha) and PGE(2) on Days 12, 14, and 16 of the estrous cycle and pregnancy in sheep. Our results indicate that luteal PG biosynthesis is selectively directed towards PGF(2alpha) at the time of luteolysis and towards PGE(2) during the establishment of pregnancy. Moreover, the ability of the CL of early pregnancy to resist luteolysis is due to increased intraluteal biosynthesis of PGE(2) and PGE(2) receptor (PTGER) 2 (also known as EP2)- and PTGER4 (also known as EP4)-mediated signaling. We also found that IFNT protein is not transported through the UOP from the uterus to the ovary; in contrast, a large proportion of endometrial PGE(2) is transported from the uterus to the ovary through the UOP. These results indicate that endometrial PGE(2) stimulated by pregnancy is transported locally to the ovary, which increases luteal PGE(2) biosynthesis and hence activates luteal PTGER2 and PTGER4 signaling, thus protecting the CL during the establishment of pregnancy in sheep.

Differential Expression of the Enzymatic System Controlling Synthesis, Metabolism, and Transport of PGF2 Alpha in Human Fetal Membranes1

The present study investigated the expression of genes and proteins associated with PGF2alpha biosynthesis, catabolism, and transport in matched amnion and choriodecidua of human term placenta. The concentration of PGF2alpha within fetal membranes depends on the balance between complex enzymatic systems responsible for, respectively, its synthesis-by prostaglandin-endoperoxide synthase 2 (PTGS2) and members of the aldo-keto reductase (AKR) family, AKR1C3 and AKR1B1-and its catabolic inactivation-through hydroxy-prostaglandin-dehydrogenase (HPGD). We observed that AKR1C3 shows equal basal expression (mRNA and protein) in choriodecidua and amnion but that AKR1B1 exhibits preferential expression in the choriodecidua. Expression of HPGD and solute carrier organic anion transporter family member 2A1 (SLCO2A1) was found primarily in the choriodecidua. We also evaluated whether an inflammatory environment induced by the gram-negative bacterial endotoxin lipopolysaccharide (LPS) affects expression of each candidate enzymes. The amnion responded to LPS with a small but significant decrease of AKR1B1 mRNA expression. In contrast, we found a significant increase in PTGS2 and AKR1C3 mRNA expression in choriodecidua after LPS challenge, but such regulation was confirmed only at protein levels for PTGS2 and not for AKR1C3. Our results suggest that the choriodecidua appears to be the main tissue, which expresses maximally all the components (synthesis, degradation, and transport) controlling PGF2alpha levels.

Lysophosphatidic Acid Action During Early Pregnancy in the Cow: In Vivo and In Vitro Studies

We have previously documented synthesis of lysophosphatidic acid (LPA) in the bovine endometrium and the increased presence of LPA receptor mRNA expression during pregnancy. Therefore, LPA could contribute to early pregnancy establishment in the cow. In the present study, we investigated the effect of intravaginally administered LPA on pregnancy rates and on the plasma levels of progesterone (P4) and prostaglandins (PGs) in heifers. Animals were inseminated and from day 15 to 18 after estrus were treated intravaginally with saline, LPA (1 mg) or LPA receptor blocker (VPC32183; 1 mg). Blood samples were collected on days 0, 6, 12, 15, 16, 17, 18 and 21 after insemination. Pregnancy was confirmed by ultrasonography and per rectum examination on days 30 and 49-50 after insemination. Intravaginal LPA administration increased the plasma P4 and PGE(2) concentrations compared with saline and VPC32183-treated heifers. In the saline and LPA-treated groups, 6 out of 8 heifers were pregnant (75%), whereas the pregnancy rate in the VPC32183-treated heifers was only 37%. We also examined the effects of LPA on PG secretion and PG synthase mRNA expression in stromal and epithelial cells of the bovine endometrium on days 16-18 of pregnancy and the estrous cycle. LPA increased PGE(2) production and PGE(2) synthase (PGES) mRNA expression in stromal cells during the estrous cycle and pregnancy. On Days 16-18 of pregnancy, LPA inhibited PGF(2alpha) production and PGFS mRNA expression in epithelial cells. The results suggest that LPA serves as a luteotropic factor during the estrous cycle and pregnancy, stimulating P4 secretion in vivo and PGE(2) secretion in vitro through activation of PGES mRNA expression in stromal cells. Moreover, during the early pregnancy, LPA decreases PGF(2alpha) synthesis and mRNA expression for PGFS in epithelial cells of the bovine endometrium.

Prostaglandin Synthesis, Metabolism, and Signaling Potential in the Rhesus Macaque Corpus Luteum throughout the Luteal Phase of the Menstrual Cycle

Prostaglandins in the corpus luteum (CL) reportedly serve as luteotropic and luteolytic agents. Based mainly on studies conducted in domesticated animals and rodents, prostaglandin E2 (PGE2) is generally considered a luteotropic factor, whereas uterine-derived prostaglandin F2alpha (PGF2alpha) initiates luteolysis. However, the role of prostaglandins in regulating primate luteal structure-function is poorly understood. Therefore, a comprehensive analysis of individual mRNA or proteins that are involved in PGE2 and PGF2alpha biosynthesis, metabolism, and signaling was performed using CL obtained at distinct stages of the luteal life span during the menstrual cycle in rhesus monkeys. Peak levels of proteins involved in PGE2 synthesis (prostaglandin-endoperoxide synthase 2, microsomal PGE2 synthase-1) and signaling (PGE2 receptor 3) occurred during periods corresponding to development and maintenance of the primate CL. Immunohistochemistry studies indicated that large luteal cells express PGE2 synthesizing and signaling proteins. Expression of PGE2 synthesizing and signaling proteins significantly decreased preceding the period of functional regression of the CL, which also coincided with increasing levels of PGF2alpha receptor protein expression within the large luteal cells. Moreover, significant levels of mRNA expression for several aldoketo reductase family members that synthesize PGF2alpha from other prostaglandins were observed throughout the rhesus macaque luteal phase, thus supporting the possibility of intraluteal PGF2alpha production. Collectively, our results indicate that there may be intraluteal synthesis and signaling of PGE2 during development and maintenance of the primate CL, followed by a shift to intraluteal PGF2alpha synthesis and signaling as the CL nears the time of luteolysis.

Differential regulation of myometrial prostaglandin production by changes in length

The purpose of this study was to determine whether stretching and shortening of human myometrial strips alters prostaglandin production. We measured 6-keto prostaglandin F1alpha (PGF1alpha; a PGI2 metabolite) and PGF2alpha in the contraction baths of myometrial strips that were obtained at cesarean delivery from 5 term pregnant women. Fluid was collected after the stretching and after the strip lengths were decreased by 4%, 6%, or 8%. Prostaglandin concentrations were measured in triplicate by competitive enzyme immunoassay and compared by Kruskal-Wallis tests. Stretching myometrial strips increased the production of 6-keto PGF1alpha by 31%, but not PGF2alpha. Shortening strips had little effect on 6-keto PGF1alpha production, but increased PGF2alpha production by 158%. Stretching myometrial strips from pregnant women increases synthesis of PGI2; shortening strips increases synthesis of PGF2alpha. Differential prostaglandin synthesis that is related to myometrial stretching and shortening could play a role in uterine quiescence during gestation and increased contractility during parturition.

The Role of the Endometrium in Endocrine Regulation of the Animal Oestrous Cycle

A critical analysis of the results of research in the function of the endometrium was carried out and a view point presented. The role of the endometrium in endocrine regulation of the oestrus cycle can be summarized as follows: 1. The transfer of prostaglandin F(2alpha) (PGF(2alpha)) from the uterus to an ovary, which causes luteolysis, occurs mainly via the lymphatic pathways. 2. The system of retrograde transfer of PGs enables PGF(2alpha) and PGE(2) to reach the myometrium and endometrium with arterial blood at high concentration. In the luteal phase, PGF(2alpha), together with the increasing concentration of progesterone, constricts the arterial vessels of the uterus; in the follicular phase and in early pregnancy, PGE(2) together with oestrogen and embryonic signals, relaxes the arterial vessels. In addition, this system protects the corpus luteum from premature luteolysis during the cycle and luteolysis during early pregnancy. 3. In days 10-12 of the cycle, the blood flow in the uterus decreases by 60-70% in pigs and around 90% in sheep. This causes ischaemia and local hypoxia confirmed by the presence of hypoxia inducible factor and thus remodelling of the endometrium commences. 4. The pulsatile elevations in PGF(2alpha) concentration occurring in the blood flowing out of the uterus during the period of luteolysis and the next few days, do not result from increased PGF(2alpha) synthesis as suggested in numerous studies. They are the effect of excretion of PGF(2alpha) and its metabolites together with lymph and venous blood and tissue fluids in which prostaglandin accumulates.

Judge, jury and executioner: the auto-regulation of luteal function

Experiments were conducted to further our understanding of the cellular and molecular mechanisms that regulate luteal function in ewes. Inhibition of protein kinase A (PKA) reduced (P < 0.05) secretion of progesterone from both small and large steroidogenic luteal cells. In addition, the relative phosphorylation state of steriodogenic acute regulatory protein (StAR) was more than twice as high (P < 0.05) in large vs small luteal cells. Large steroidogenic luteal cells appear to contain constitutively active PKA and increased concentrations of phosphorylated StAR which play a role in the increased basal rate of secretion of progesterone. To determine if intraluteal secretion of prostaglandin (PG) F2alpha was required for luteolysis, ewes on day 10 of the estrous cycle received intraluteal implants of a biodegradable polymer containing 0, 1 or 10 mg of indomethacin, to prevent intraluteal synthesis of PGF2alpha. On day 18, luteal weights in ewes receiving 1 mg of indomethacin were greater (P < 0.05) than controls and those receiving 10 mg were greater (P < 0.05) than either of the other two groups. Concentrations of progesterone in serum were also increased (P < 0.05) from days 13 to 16 of the estrous cycle in ewes receiving 10 mg of indomethacin. Although not required for decreased production of progesterone at the end of the cycle, intraluteal secretion of PGF2alpha appears to be required for normal luteolysis. To ascertain if oxytocin mediates the indirect effects of PGF2alpha on small luteal cells, the effects of 0, 0.1, 1 or 10 mM oxytocin on intracellular concentrations of calcium were quantified. There was a dose-dependent increase (P < 0.05) in the number of small luteal cells responding to oxytocin. Thus, oxytocin induces increased calcium levels and perhaps apoptotic cell death in small luteal cells. Concentrations of progesterone, similar to those present in corpora lutea (approximately 30 microg/g), prevented the increased intracellular concentrations of calcium (P < 0.05) stimulated by oxytocin in small cells. In large luteal cells the response to progesterone was variable. There was no consistent effect of high quantities of estradiol, testosterone or cortisol in either cell type. It was concluded that normal luteal concentrations of progesterone prevent the oxytocin and perhaps the PGF2alpha-induced increase in the number of small and large luteal cells which respond to these hormones with increased intracellular concentrations of calcium. In summary, large ovine luteal cells produce high basal levels of progesterone, at least in part, due to a constituitively active form of PKA and an enhanced phosphorylation state of StAR. During luteolysis PGF2alpha of uterine origin reduces the secretion of progesterone from the corpus luteum, but intraluteal production of PGF2alpha is required for normal luteolysis. Binding of PGF2alpha to receptors on large luteal cells stimulates the secretion of oxytocin which appears to activate PKC and may also inhibit steroidogenesis in small luteal cells. PGF2alpha also activates COX-2 in large luteal cells which leads to secretion of PGF2alpha. Once intraluteal concentrations of progesterone have decreased, oxytocin binding to its receptors on small luteal cells also results in increased levels of intracellular calcium and presumably apoptosis. Increased secretion of PGF2alpha from large luteal cells activates calcium channels which likely results in apoptotic death of this cell type.

Resistance exercise and cyclooxygenase (COX) expression in human skeletal muscle: Implications for COX‐inhibiting drugs and protein synthesis

We have shown that ibuprofen and acetaminophen block cyclooxygenase (COX) synthesis of prostaglandin PGF(2alpha) and the muscle protein synthesis increase following resistance exercise. Confusingly, these two drugs are purported to work through different mechanisms, with acetaminophen apparently unable to block COX and ibuprofen able to nonspecifically block COX-1 and COX-2. A recently discovered intron-retaining COX, now known to have three variants, has been shown to be sensitive to both drugs. We measured the expression patterns and levels of the intron 1-retaining COX-1 variants (-1b1, -1b2, and -1b3), COX-1, and COX-2 at rest and following resistance exercise to help elucidate the COX through which PGF(2alpha), ibuprofen, and acetaminophen regulate muscle protein synthesis. Skeletal muscle biopsy samples were taken from 16 individuals (8M, 8F) before, 4, and 24 h after a bout of resistance exercise and analyzed using real-time RT-PCR. Relatively few individuals expressed the intron 1-retaining COX-1b variants (COX-1b1, -1b2, and -1b3) at any time point, and when expressed, these variants were in very low abundance. COX-1 was the most abundant COX mRNA before exercise and remained unchanged (P > 0.05) following exercise. COX-2 was not expressed before exercise, but increased significantly (P < 0.05) at 4 and 24 h after exercise. The inconsistent and low levels of expression of the intron 1-retaining COX-1 variants suggest that these variants are not likely responsible for the inhibition of PGF(2alpha) production and skeletal muscle protein synthesis after resistance exercise by ibuprofen and acetaminophen. Skeletal muscle-specific inhibition of COX-1 or COX-2 by these drugs should be considered.

Prostaglandin F2α and Its Receptor as Activators of Human Decidua

Prostaglandins produced by the intrauterine tissues of both mother and fetus (myometrium, decidua, placenta, chorion, and amnion) are involved with all of the physiologies of parturition (membrane rupture, cervical dilatation, myometrial contractility, placental separation, and uterine involution). For parturition to occur, however, the intrauterine tissues need to first be activated to prepare for the work of labor, then stimulated to initiate labor. Prostaglandins normally are considered to be stimulators of the physiologies of labor. This review presents evidence that one prostaglandin, PGF2alpha, and its receptor, FP, are also activators, especially of the decidua. Stimulated by cytokines, the decidual synthesis of PGF2alpha and the expression of FP lead to increased matrix metalloproteinase activity, further enhancement of cytokine activity, increased decidual oxytocin and oxytocin receptor expression, decreased progesterone responsiveness, and possibly, enhanced expression of vascular endothelial growth factor. These collective actions prepare the decidua for its role in parturition.

Fish meal supplementation alters uterine prostaglandin F2α synthesis in beef heifers with low luteal-phase progesterone1,2

The objective of the current study was to evaluate the effect of omega-3 fatty acids in fish meal on mitigating uterine PGF2alpha synthesis in heifers with low luteal-phase concentrations of progesterone. Animals were individually fed a corn silage-based diet supplemented with fish meal (5% of DMI; n = 12) or corn gluten meal (6% of DMI; n = 13). Estrous cycles were synchronized using PGF2alpha beginning on d 25 of supplementation. Random heifers from each supplement group (n = 6 fish meal, and n = 7 corn gluten meal) were given three additional i.m. injections of PGF2alpha (25 mg) at 12-h intervals beginning at 0600 on d 3 after estrus to induce formation of corpora lutea that secrete lower concentrations of progesterone. Jugular blood samples were collected daily commencing on d 1 and continuing through d 16 of the estrous cycle to determine serum progesterone concentrations. Oxytocin was administered i.v. (100 IU) to heifers on d 16 after estrus to stimulate uterine PGF2alpha synthesis. Before statistical analyses, heifers were sorted to either normal or low luteal-phase progesterone as determined from serum progesterone on d 9 of the estrous cycle. After sorting, treatment groups consisted of 1) normal luteal progesterone + fish meal (n = 6); 2) low luteal progesterone + fish meal (n = 6); 3) normal luteal progesterone + corn gluten meal (n = 6); and 4) low luteal progesterone + corn gluten meal (n = 7). Serum concentrations of the PGF2alpha metabolite following oxytocin stimulation tended (P = 0.09) to be greater in heifers with low luteal-phase progesterone compared with heifers with normal luteal-phase progesterone. Fish meal supplementation mitigated this response in heifers with low luteal-phase progesterone (P < 0.05), but had no effect on heifers with normal luteal-phase progesterone. In conclusion, the omega-3 fatty acids in fish meal seem to decrease uterine PGF2alpha synthesis in heifers with low luteal-phase serum concentrations of progesterone.

Biological activity of recombinant bovine interferon tau using an Autographa californica nuclear polyhedrosis virus expression system.

Bovine interferon (bIFN) tau, which plays a key role in maternal-fetal recognition of pregnancy, was expressed by an Autographa californica nuclear polyhedrosis virus expression system. cDNA coding bIFNtau was derived from cultured trophoblast cells. The recombinant (r) bIFNtau had high antiviral activity (1 x 10 (8) IU/mg) and the molecular weight of rbIFNtau was estimated to be 23 kDa by Western blotting analysis. We investigated the biological effect of rbIFNtau on prostaglandin (PG) F(2alpha) synthesis in cultured bovine endometrial epithelial cells in the presence or absence of oxytocin (OT, 100 nM). rbIFNtau suppressed basal and OT-induced PGF(2alpha) production in a dose-dependent manner (1-1,000 ng/ml). These results showed that biologically active rbIFNtau was produced in the baculovirus expression system, and that rbIFNtau had the ability to suppress the synthesis of PGF(2alpha) from bovine endometrial epithelial cells.

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.

Decreased superoxide dismutase expression and increased concentrations of lipid peroxide and prostaglandin F(2alpha) in the decidua of failed pregnancy.

To study the possible role of the superoxide radical and its scavenging system in the decidua of early pregnancy, superoxide dismutase (SOD) values and concentrations of lipid peroxide and prostaglandin F(2alpha) (PGF(2alpha)) were analysed in the decidua obtained from normal pregnancy and failed pregnancy. Failed pregnancy was divided into two groups; spontaneous abortion with or without vaginal bleeding. In the spontaneous abortion with vaginal bleeding, total SOD activities, Cu,Zn-SOD activities and Cu,Zn-SOD mRNA values in the decidua were significantly lower, and concentrations of lipid peroxide and PGF(2alpha) were significantly higher, than those in the normal pregnancy and the spontaneous abortion without vaginal bleeding. In contrast, activities and mRNA values of Mn-SOD were significantly higher in the spontaneous abortion with vaginal bleeding than the other two groups. There was no significant difference in all of these parameters between the normal pregnancy and the spontaneous abortion without vaginal bleeding. In conclusion, the decrease in Cu,Zn-SOD expression and the increase in lipid peroxide in the decidua could be involved in the termination of spontaneous abortion, mediated through the increase in PGF(2alpha) synthesis. In other words, Cu,Zn-SOD may contribute to the maintenance of pregnancy by preventing the accumulation of superoxide radicals that cause PGF(2alpha) synthesis.

Effects of inhibitors of arachidonic acid turnover on the production of prostaglandins by the guinea-pig uterus.

The supply of free arachidonic acid from phospholipids is generally regarded as the rate-limiting step for prostaglandin (PG) synthesis by tissues. Two enzymes involved in arachidonic acid uptake into, and release from, phospholipids are acyl-CoA:lysophospholipid acyltransferase (ACLAT) and phospholipase A2 (PLA2), respectively. PGF2 alpha produced by the endometrium induces luteolysis in several species including guinea-pigs. Thimerosal, an inhibitor of ACLAT, and aristolochic acid, an inhibitor of PLA2, both reduced, in a concentration-dependent manner, the output of PGF2 alpha from guinea-pig endometrium cultured for 24 h on days 7 and 15 of the oestrous cycle. This study showed that the continual production of PGF 2 alpha by guinea-pig endometrium is not only dependent upon the activity of PLA2 for releasing free arachidonic acid for PGF2 alpha synthesis, but also on the incorporation of arachidonic acid into the phospholipid pool by the activity of ACLAT. The inhibitory effects of thimerosal and aristolochic acid on the outputs of PGE2 and 6-keto-PGF1 alpha were less marked, particularly on day 7 when the low output of PGE2 was unaffected and the output of 6-keto-PGF1 alpha was increased at the lower concentrations of thimerosal. This finding indicates that there are different pools of arachidonic acid bound as phospholipid for the syntheses of PGF2 alpha and 6-keto-PGF1 alpha by guinea-pig endometrium.

Effects of inhibitors of arachidonic acid turnover on the production of prostaglandins by the guinea-pig uterus

The supply of free arachidonic acid from phospholipids is generally regarded as the rate-limiting step for prostaglandin (PG) synthesis by tissues. Two enzymes involved in arachidonic acid uptake into, and release from, phospholipids are acyl-CoA:lysophospholipid acyltransferase (ACLAT) and phospholipase A2 (PLA2), respectively. PGF2 alpha produced by the endometrium induces luteolysis in several species including guinea-pigs. Thimerosal, an inhibitor of ACLAT, and aristolochic acid, an inhibitor of PLA2, both reduced, in a concentration-dependent manner, the output of PGF2 alpha from guinea-pig endometrium cultured for 24 h on days 7 and 15 of the oestrous cycle. This study showed that the continual production of PGF 2 alpha by guinea-pig endometrium is not only dependent upon the activity of PLA2 for releasing free arachidonic acid for PGF2 alpha synthesis, but also on the incorporation of arachidonic acid into the phospholipid pool by the activity of ACLAT. The inhibitory effects of thimerosal and aristolochic acid on the outputs of PGE2 and 6-keto-PGF1 alpha were less marked, particularly on day 7 when the low output of PGE2 was unaffected and the output of 6-keto-PGF1 alpha was increased at the lower concentrations of thimerosal. This finding indicates that there are different pools of arachidonic acid bound as phospholipid for the syntheses of PGF2 alpha and 6-keto-PGF1 alpha by guinea-pig endometrium.