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This experiment was performed to evaluate whether intrafollicular treatment of PGE2 or PGF2α administered in early estrus would induce normal ovulation, progesterone production (Experiment 1) and pregnancy (Experiment 2). In Experiment 1, mares in estrus after 2 days of endometrial edema were injected in all largest dominant follicles (28-35 mm in diameter) with 0.5 mL of sterile water containing 500 μg PGE2 (n = 6), 125 μg PGF2α (n = 6) or placebo (n = 7) (Hour 0). Ultrasound examinations were performed daily, until ovulation or anovulation was detected, and daily blood samples were taken for 8 days. In Experiment 2, mares with a dominant follicle ≥35 mm after at least three days of slight-to-moderate endometrial edema, were injected with 500 μg PGE2 diluted in 0.5 mL of sterile water for injection in the follicle (PGE2 group; n = 9 mares and 11 dominant follicles). No puncture was performed in the control group (n = 9 mares and 11 dominant follicles). Mares from both groups were inseminated. In Experiment 1, all mares (6/6) in the PGE2 group ovulated within 24 h of treatment. The mean interval from intrafollicular injection to ovulation was shorter (P < 0.001) in PGE2 mares (24 ± 0 h) than in control mares (77 ± 9 h). Mares from the PGF2α group developed hemorrhagic anovulatory follicles (HAF) more often (7/7) than control mares (2/7); P < 0.05). The progesterone concentration in mares from the PGF2α group was lower (P < 0.004) than control mares in the early post-ovulatory period. The first significant increase in post-ovulatory progesterone concentration occurred earlier (P < 0.05) in mares from the control group than in mares from the PGF2α and PGE2 groups. In Experiment 2, more mares from the control group (7/9, 78 %) became pregnant than from the PGE2 group (2/9, 22 %) (P = 0.015). In conclusion, PGE2 alone induced follicle collapse in all treated mares within 24 h of administrations, while PGF2α blocked ovulation and induced formation of HAFs. However, the post-ovulatory rise in progesterone production was delayed and the fertility reduced in mares with ovulation induced by PGE2 compared to control mares., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

We aimed to elucidate the effects of PGE2 and PGF2α on the in vitro maturation (IVM) of bovine oocytes. First, cumulus-oocyte complexes were matured in the media supplemented with or without PGE2, PGF2α, or PGE2 plus PGF2α for the final 24, 12, or 6 h of culture. Then, the cumulus-oocyte complexes were matured in the absence or presence of a PG endoperoxide synthase 2 (PTGS2) enzyme inhibitor (NS398) supplemented with PGE2, PGF2α, or PGE2 plus PGF2α. Finally, the expression of genes associated with PGs activity in cumulus cells (PTGS2, PG E-synthase-1 [PTGES1], and aldo-keto reductase 1 [AKR1B1]) or oocytes (receptors for PGE2 [PTGER2] and PGF2α [PTGFR]) of different competencies was quantified. Supplementation of the IVM medium with PGs did not improve in vitro embryo production or embryo quality (P > 0.05). During maturation, the relative abundance of PTGS2 transcripts increased (P < 0.05) only in the less-competent group, whereas those of PTGES1 increased in the less-competent and in the more-competent groups. Conversely, AKR1B1 expression decreased only in the less-competent group (P < 0.05). Receptors for the PGE2 and PGF2α genes were very low or undetectable in oocytes. In conclusion, PGE2 and PGF2α are not recommended for media supplementation during maturation because they have no effect on embryo development. Although genes related to PGs activity are differentially expressed in cumulus cells of cumulus-oocyte complexes of different competence during maturation, the expression of PGE2 and PGF2α receptor genes was either not detectable or was detected at low levels in oocytes., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Prostaglandins (PG) have primary functions in the reproductive tract, however, the mechanism of regulation of PG secretion in the endometrium is unclear. Estrogen as a predominant regulator of uterine functions during the mammalian estrous cycle and effects of estrogen on synthesis of PG and function in uterine tissues of cattle are not fully understood. In this study, there was evaluation of the concentration- and time-effects of 17β-estradiol on PG synthesis in endometrial explants of cattle, focusing on the secretion of prostaglandin E 2 (PGE 2 ) and prostaglandin F 2α (PGF 2α ) as well as relative abundance of mRNA transcript and protein for both the enzymes responsible for PGE 2 and PGF 2α synthesis, including prostaglandin-endoperoxide synthase 1 and 2 (PTGS1, PTGS2), PGE 2 synthase (PGES), PGF 2α synthase (PGFS), and carbonyl reductase (CBR1), and the receptors responsible for downstream PGE 2 (PTGER2, PTGER4) and PGF 2α (PTGFR) signaling. Results indicated that 17β-estradiol increased PGE 2 and PGF 2α production at concentrations ranging from 10 -11 to 10 -8 M. Furthermore, abundances of PTGS1, PTGS2, PGES, PGFS, PTGER2, PTGER4, and PTGFR mRNA transcripts and protein were greater immediately after 17β-estradiol treatment at almost all the concentrations, while these CBR1 abundances were less as a result of treatments with 17β-estradiol. These data support the hypothesis that estradiol modulates the synthesis and function of PG in the endometrium of cattle., Competing Interests: Declarations of Competing Interest The authors declare that they have no conflicts of interests., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Studies have demonstrated that adiponectin could be a link between reproductive functions and energy metabolism in animals. The aim of the present study was to investigate the effects of prostaglandin (PG) E 2 and PGF 2α (10, 50, 100, 250 and 500ngmL -1 ) on the expression and secretion of adiponectin and its receptor genes and proteins by cultured in vitro porcine endometrial and myometrial tissues on Days 10-28 of pregnancy and Days 10-11 of the oestrous cycle. The gene expression was analysed using the real-time PCR method. Adiponectin protein secretion was determined by ELISA, whereas the receptors proteins content was defined using Western Blot analysis. Both PGE 2 and PGF 2α modulated the expression of adiponectin system genes and proteins in the uterus during early pregnancy. PGE 2 and PGF 2α had similar effects on the adiponectin system, which differed between the stages of gestation and between pregnancy and the oestrous cycle. On Days 10-11 of gestation, PGE 2 and PGF 2α generally increased adiponectin secretion by endometrial and myometrial tissues. Both PGs decreased levels of endometrial adiponectin receptor type 1 (AdipoR1), whereas only PGF 2α decreased myometrial levels of AdipoR1. Both PGs increased myometrial adiponectin receptor type 2 (AdipoR2) levels. On Days 12-13 of gestation, PGE 2 decreased AdipoR1 concentrations in both tissues and AdipoR2 levels in the endometrium. PGF 2α decreased myometrial concentrations of both receptors. On Days 15-16 of gestation, both PGE 2 and PGF 2α increased concentrations of AdipoR1 and AdipoR2 in the endometrium and myometrium. PGE 2 stimulated the secretion of adiponectin in the endometrium, but not in the myometrium. On Days 27-28 of pregnancy, both PGE 2 and PGF 2α inhibited the expression of AdipoR1 and AdipoR2 in endometrial and myometrial tissues and decreased the secretion of endometrial adiponectin. Both PGE 2 and PGF 2α had tissue-specific and dose-dependent effects on the adiponectin system.

Mammalian reproductive function is controlled by the hypothalamic-pituitary-gonadal (HPG) axis, which is suppressed under infectious stress conditions. By analysing the pulsatility of luteinising hormone (LH), we have previously demonstrated that prostaglandins (PGs) in the central nervous system mediate infectious stress to suppress the activity of the HPG axis. The present study aimed to characterise the types of PGs responsible for suppression of the HPG axis. We focused on three major types of PGs: PGE 2 , PGD 2 and PGF 2α . We used female rats overiectomised bilaterally 1 week before the experiments. Lipopolysaccharide (100 μg kg -1 ) suppressed LH pulses at the same time as enhancing the concentration of all three PGs in the cerebrospinal fluid, which was restored by indomethacin (10 mg kg -1 ). Subsequently, we observed LH pulsatility after a single injection of each PG and after co-injection of PGE 2 with PGF 2α into the third cerebral ventricle. A single injection of PGE 2 dose-dependently induced a transient increase in mean LH concentration and LH pulse amplitude, and PGD 2 significantly increased the amplitude of LH pulses, wereas PGF 2α did not affect LH pulsatility. On the other hand, co-injection of PGE 2 and PGF 2α induced a significant suppression of both the frequency and amplitude of LH pulses. These results suggest that PGE 2 and PGF 2α can represent two of the mediators that suppress the HPG axis in situations of infectious stress. Moreover, the results imply that there are two contradictory effects of PGE 2 on LH pulsatility: (i) enhancive when working alone and (ii) suppressive when working together with PGF 2α ., (© 2017 British Society for Neuroendocrinology.)

Prostaglandins (PGs) have been shown to cause several physiological changes in mammals including anorexia, awakening and sleeping, change in digestive function, and activation of the hypothalamus-pituitary-adrenal gland (HPA) axis. However, there is a paucity of information about the effect of PGs on physiological parameters in birds. The purpose of the present study was to clarify whether intracerebroventricular (ICV) and intraperitoneal (IP) injections of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) affect feeding, voluntary movement, crop-emptying rate, and corticosterone release in chicks (Gallus gallus). ICV injection of either PGE2 or PGF2α (2 and 4μg) significantly decreased food intake in chicks. The anorexigenic effect was also observed after IP injection of the PGs. Voluntary movement was significantly suppressed by ICV injection of PGE2 or PGF2α, although the time-course change was different between the two. In contrast, IP injection of the PGs had no or less effect on voluntary movement. Both ICV and IP injection of PGE2 significantly retarded the crop-emptying rate, whereas PGF2α significantly lowered the crop-emptying rate only after IP injection. The plasma corticosterone concentration significantly increased after ICV and IP injection of PGE2, whereas PGF2α had no effect. These results suggest that central and peripheral PGs are involved in the regulation of appetite, voluntary movement, food passage in the digestive tract, and activation of the HPA axis in chicks, although the effects depend on the site of action and type of PGs., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The objectives were to determine: (i) whether intrafollicular administration of PGE2 and PGF2α to mares would hasten follicle collapse and (ii) the differences in reproductive hormone characteristics in mares with spontaneous and prostaglandin-induced follicle collapses. Six mares were followed for two oestrous cycles each: when the mares reached a follicle diameter of 30-35 mm and showed mild-to-moderate endometrial oedema, mares were administered a single 0.5 ml dose containing 500 μg PGE2 and 125 μg PGF2α (treatment cycle) or a placebo (0.5 ml of water for injection; control cycle) into the preovulatory follicle (Hour 0). Blood samples were collected, and serial ultrasound examinations were performed until follicle collapse. Treated mares showed follicle collapse significantly earlier (20.0 ± 5.9 h) than the control mares (72.0 ± 10.7 h). The LH, progesterone, total oestrogens and oestradiol concentrations did not differ between groups; however, the progesterone concentration increased more between 48 and 72 h after follicle injection in the treatment compared to the control cycles (P < 0.05). In conclusion, intrafollicular treatment with PGE2 and PGF2α hastened follicle collapse in mares without the simultaneous use of an inductor of ovulation; despite the early induction of follicle collapse, the profiles of LH and oestradiol were not altered. This study provides information on the role of prostaglandins (PGs) in the process of follicle wall rupture and collapse and suggests that this may happen even before the beginning of the sharp rise in circulating LH at the final stage of the ovulatory surge., (© 2016 Blackwell Verlag GmbH.)

Reasons for Performing Study: Haemorrhagic anovulatory follicle is the most common pathological anovulatory condition in the mare, but its cause remains unknown. An experimental model to induce luteinised unruptured follicles (LUF) with flunixin-meglumine (FM) has been developed. Luteinised unruptured follicles share similar morphological and hormonal characteristics with haemorrhagic anovulatory follicles., Objectives: To test the effect of intrafollicular administration of prostaglandins PGE2 and PGF2α during the periovulatory period on ovulation and pregnancy in FM-treated mares., Study Design: In vivo experiment in a crossover design., Methods: Five mares were followed during 2 oestrous cycles each. All mares were given FM at 1.7 mg/kg bwt i.v. every 12 h from Hour 0 (Hour 0 = human chorionic gonadotrophin treatment) to Hour 36. In treatment cycles (n = 5), at Hour 32 the preovulatory follicle was punctured and 0.5 ml of a solution containing 500 μg of PGE2 and 125 μg of PGF2α was deposited within the follicle. In control cycles, water for injection was administered into the follicle at the same time. In 3 control and 3 treatment cycles, mares were also inseminated at Hour 24. Diagnosis of ovulation/LUF formation and pregnancy was performed by ultrasound examination between Hours 36 and 72 and 14 days after ovulation/LUF formation, respectively., Results: During the treatment cycles, all mares ovulated normally (100% ovulation rate) 36-48 h after human chorionic gonadotrophin, while in 4 of 5 control cycles the mares developed an LUF (80%, P<0.05). All 3 inseminated mares became pregnant in the treatment cycles, but not in the control cycles., Conclusions: Intrafollicular treatment with PGE2 and PGF2α overcame the anovulatory effect of FM. This sheds new insights into the knowledge on the possible therapeutic options for ovulatory failure in the mare., (© 2015 EVJ Ltd.)

Prostaglandins (PGs) have been reported to be present in the seminal fluid and cervical mucus, affecting different stages of sperm maturation from spermatogenesis to the acrosome reaction. This study assessed the effects of low physiological PGE2 and PGF2α concentrations on human sperm motility and on the ability of the spermatozoa to bind to the zona pellucida (ZP). Human spermatozoa were isolated from seminal samples with normal concentration and motility parameters and incubated with 1μM PGE2, 1μM PGF2α or control solution to determine sperm motility and the ability to bind to human ZP. The effects of both PGs on intracellular calcium levels were determined. Incubation for 2 or 18h with PGE2 or PGF2α resulted in a significant (P<0.05) increase in the percentage of spermatozoa with progressive motility. In contrast with PGF2α, PGE2 alone induced an increase in sperm intracellular calcium levels; however, the percentage of sperm bound to the human ZP was doubled for both PGs. These results indicate that incubation of human spermatozoa with low physiological levels of PGE2 or PGF2α increases sperm functions and could improve conditions for assisted reproduction protocols.

In order to characterize the transition of the corpora lutea (CL) from acquisition of luteolytic sensitivity to rescue of luteal function: i) the expression of 38 factors associated with steroids, prostanoids, and angiogenic systems and ii) concentrations of the main hormones responsible for maintenance of CL function in cyclic and pregnant pigs were examined. Additionally, the effect of prostaglandin (PG) E2 and F2 α on luteal function during the estrous cycle and pregnancy was evaluated in vitro. Significantly up-regulated gene expression was revealed in CL collected on day 14 of the estrous cycle (CYP19A1, ESR2, PTGS2, HIF1A, and EDN1) and on days 12-14 of pregnancy (SCARB1, PGRMC1, STAR, HSD3B1, NR5A1, PTGFR, PTGER4, and VEGFA). Elevated concentrations of estradiol-17β and PGE2 occurred in CL on days 12 and 14 of pregnancy respectively, while an increased intraluteal PGF2 α content was noted on day 14 of the estrous cycle. Both PGs increased the synthesis of progesterone by cultured luteal slices obtained on day 14 of pregnancy, in contrast to the action of PGF2 α on the corresponding day of the estrous cycle. PGE2 stimulated cAMP production via PTGER2 and PTGER4, while PGF2 α elevated the content of CREB in cultured luteal slices from CL of pregnant pigs. In silico analysis showed that infiltration of lymphocytes and apoptosis of microvascular endothelium were activated in CL on day 12 of the estrous cycle vs pregnancy. Summarizing, an abundance of E2 and PGE2 during pregnancy regulates specific pathways responsible for steroidogenesis, the prostanoid signaling system and angiogenesis during rescue from luteolysis in porcine CL., (© 2016 Society for Reproduction and Fertility.)

The cellular basis for the regulation of retinal blood flow is unknown, but recently a new type of perivascular cell (PVC) with pericyte characteristics was identified in the retinal arterial vascular wall located immediately external to the vascular smooth muscle cells. A possible involvement of this cell type in the regulation of retinal vascular tone might be elucidated by studying differences in the response after the addition of compounds stimulating respectively relaxation and contraction. The effects of PGE2 and PGF2α on vascular tone and calcium activity in PVCs in porcine retinal arterioles were studied in a confocal myograph after the addition of the ryanodine receptor blocker ryanodine, the L-type Ca(2+) channel blocker nifedipine, the non-specific cation channel blocker LOE908, the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) blocker CPA, and the inositol triphosphate receptor (IP3R) and transient receptor potential (TRP) ion channel blocker 2-APB. The Ca(2+) channel blockers nifedipine and LOE908 induced significant relaxation of retinal arterioles. After the addition of both PGE2 and PGF2α calcium activity in the PVCs was significantly reduced by both the SERCA inhibitor CPA and the IP3R antagonist 2-APB, but the changes in calcium activity were unrelated to the changes in tone induced by PGE2 and PGF2α. Changes in the tone of porcine retinal arterioles in vitro induced by PGE2 and PGF2α involve other factors than calcium activity in the perivascular cells., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objective: To describe the physiological activity of the myometrium in oestrus and dioestrus and the induced activity after medication in cows with particular reference to segmental differences., Material and Methods: Six cows were given the pharmaceuticals carbetocin, oxytocin and prostaglandin (PG) F2α (dinoprost) intramuscularly and PGE2 intravenously. The physiological myometrial activity was recorded for 15 minutes and the induced activity for 105 minutes by using a transcervically attached pressure probe containing six pressure microtransducers., Results: Lower pressures were measured in dioestrus compared to oestrus before (dioestrus 3.2±8.88 mmHg, oestrus 12.4±13.23 mmHg, p<0.0001) and after the drug administration. Carbetocin provoked the longest lasting effect (60 minutes in dioestrus, 75 minutes in oestrus) followed by PGE2 (45 minutes in dioestrus, 60 minutes in oestrus), PGF2α (30 minutes each) and oxytocin (15 minutes in oestrus only). In contrast to the other drugs carbetocin did not cause any pressure decrease beneath the base level after the primary pressure increase in dioestrus. In dioestrus the pressure before drug administration was significantly higher in the cervix (3.6±19.40 mmHg) and the uterine body (7.1±36.10 mmHg) than in the uterine horn (1.1±7.21 mmHg). Conversely, in oestrus the pressure in the uterine horn (16.6±17.73 mmHg) was significantly higher than in the uterine body (6.2±16.59 mmHg) and the cervix (10.4±17.91 mmHg). Drug administration in dioestrus caused a cornual pressure increase and the pressure in the uterine body decreased, whereas in oestrus the pressure increased in all uterine segments. The physiological frequency of the pressure waves in dioestrus was 5.2±3.02 in 15 minutes compared to 7.5±2.89 in 15 minutes in oestrus. No traceable changes of the contraction frequency were found after medication., Conclusion and Clinical Relevance: Carbetocin caused the most enduring increase in intrauterine pressure in dioestrus and oestrus and may therefore be indicated best for therapeutic use. The tested drugs had the same effects on the various uterine segments and no effect on the contraction frequency.

Introduction: Vascular cell adhesion molecule (VCAM-1) plays a critical role in the inflammatory processes by stimulating the recruitment, extravasation, and migration of leukocytes. Its expression and regulation in the dental pulp is not well elucidated., Methods: Primary dental pulp cells were exposed to prostaglandin E(2) (PGE(2)), prostaglandin F(2α) (PGF(2α)), or interleukin 1β (IL-1β) with/without aspirin. VCAM-1 messenger RNA expression was analyzed by reverse transcriptase-polymerase chain reaction. Soluble VCAM-1 (sVCAM-1) in the culture medium was determined by enzyme-linked immunosorbent assay, and the number of viable cells was estimated by (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay., Results: IL-1β induced VCAM-1 gene expression of pulp cells. IL-1β also stimulated sVCAM-1 production. The IL-1β-induced sVCAM-1 production was not inhibited but rather enhanced by aspirin, a cyclooxygenase (COX) inhibitor. PGE(2) and PGF(2α) decreased the VCAM-1 expression and sVCAM-1 production of pulp cells. U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene), a mitogen-activated protein kinase kinase (MEK) inhibitor, attenuated IL-1β-induced sVCAM-1 production. However, no marked cytotoxicity was noted in these experimental conditions as analyzed by MTT assay., Conclusions: IL-1β may be involved in the pulpal inflammatory processes via stimulation of VCAM-1 expression and sVCAM-1 production. This event is not mediated by COX activation and prostanoid production but is associated with MEK signaling. PGE(2) and PGF(2α) may potentially regulate inflammatory processes by the inhibition of VCAM-1., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Objective: To determine cyclooxygenase-derived prostanoid signaling in alleviating embryo crowding in the Lpar3((-/-)) females., Design: Experimental mouse model., Setting: Research laboratories., Animal(s): Wild-type, Lpar3((+/-)), and Lpar3((-/-)) mice., Intervention(s): Intraperitoneal (IP) administration of prostaglandin E(2) (PGE(2)), cPGI (a stable analogue of PGI(2)), and 11-deoxy prostaglandin F(2α) (11-deoxy PGF(2α), a thromboxane A(2) receptor agonist) to preimplantation gestation day 3.5 Lpar3((-/-)) females., Main Outcome Measure(s): Implantation sites were detected by blue dye reaction and embryo spacing was determined by the distribution of the implantation sites along the uterine horns on gestation day 4.5; pregnancy outcome was measured by litter size at birth., Result(s): Administration of PGE(2) + cPGI on gestation day 3.5 Lpar3((-/-)) females restored on-time implantation but did not affect embryo spacing or the number of implantation sites detected on gestation day 4.5; PGE(2) + cPGI treatment increased litter size at birth. Administration of PGE(2) + cPGI + 11-deoxy PGF(2α) on gestation day 3.5 Lpar3((-/-)) females rescued on-time implantation, partially dispersed the clustered implantation sites normally observed in the Lpar3((-/-)) females, increased the number of implantation sites detected on gestation day 4.5, and increased litter size at birth., Conclusion(s): The thromboxane A(2) receptor agonist 11-deoxy PGF(2α) can partially alleviate embryo crowding in the Lpar3((-/-)) females and embryo crowding likely contributes to reduced litter size in the Lpar3((-/-)) females., (Copyright © 2012 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Prostaglandin (PG) actions on disc metabolism are unclear even though certain PGs are highly expressed by disc cells under inflammatory conditions and nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used to block PG production to treat back pain. Hence this study aimed to (1) quantify gene expression of arachidonic acid cascade components responsible for PG synthesis and (2) examine the effects of key PGs on disc matrix homeostasis. Microarray analysis revealed that inflammatory stress increases expression of synthases and receptors for prostaglandin E2 (PGE(2)) and prostaglandin F2α (PGF(2α)), resulting in elevated PGE(2) and PGF(2α) production in conditioned media of disc cells. PGE(2) diminished disc cell proteoglycan synthesis, in a dose-dependent manner. Semiquantitative RT-PCR revealed differential effects of PGE(2) and PGF(2α) on disc cell expression of key matrix structural genes, aggrecan, versican, collagens type I and II. PGE(2) and PGF(2α) also decreased message for the anabolic factor, IGF-1. PGE(2) decreased mRNA expression for the anti-catabolic factor TIMP-1 while PGF(2α) increased mRNAs for catabolic factors MMP-1 and MMP-3. Thus, PGE(2) and PGF(2α) may have an overall negative impact on disc matrix homeostasis, and the use of NSAIDs may impact disc metabolism as well as treat back pain., (Published by Wiley Periodicals, Inc. J Orthop Res 28:1259-1266, 2010.)

2-Arachidonoylglycerol is oxygenated by cyclooxygenase-2 to form prostaglandin glyceryl esters. Previous work in this laboratory has suggested that PGE(2)-G activates a novel G protein-coupled receptor in a murine macrophage-like cell line, RAW 264.7. To probe the structural determinants for the putative receptor in RAW 264.7 cells, a panel of 10 analogs was tested for their ability to increase intracellular calcium. These analogs included PGE(2)- and PGF(2alpha)-ethanolamide, 4 PGE(2) glyceryl ester analogs, and 4 PGF(2alpha) glyceryl ester analogs. The glyceryl ester analogs differed in the positioning of the hydroxyl groups in the glycerol moiety and the type of linker (ester, amide, or thioester) of the prostaglandin to the glycerol moiety. Compounds were also evaluated in a human non-small cell lung cancer cell line (H1819). The glycerol moiety was required for the calcium response. All glyceryl ester analogs but not ethanolamides caused a concentration-dependent increase in calcium levels in both RAW 264.7 and H1819 cells. An amide or ester linkage was preferable to a thioester linkage. The EC(50) values did not significantly change when the positioning of the hydroxyls was varied. This calcium response induced by the glyceryl ester analogs appears to be independent of the putative hydrolysis products, PGE(2) and PGF(2alpha), and appears to represent a novel signaling pathway., (Copyright 2010 Elsevier Inc. All rights reserved.)

The contractile effects of PGF2alpha (3 x 10(-6) to 10(-4) M) and PGE2 (10(-7) to 10(-5) M) were examined on isolated branches of ovarian artery (OA) and extramyometrial branches of uterine artery (UA) collected from pigs in the luteal (day 10-12) and follicular phase (day 17-20) of the estrous cycle, and during early pregnancy (day 10-12). Strong contraction was demonstrated in both arteries during all investigated periods in response to PGF2alpha, which was significantly higher (P < 0.01) than to PGE2, being negligible in the follicular phase. In UA, the effective dose of PGF2alpha (ED50) amounted 7.9 x 10(-6) M and 6.3 x 10(-6) M in the luteal and follicular phase, and 5.0 x 10(-6) M in early pregnancy. ED50 for PGE2 reached 5.0 x 10(-7) M in the luteal phase, and 4.1 x 10(-7) M in early pregnancy. For both prostaglandins, the contraction was much stronger (P < 0.01) in OA than in UA branches. In OA, the ED50 for PGF2alpha was 1.2 x 10(-5) M in the luteal phase and was significantly higher (P < 0.05) than in the follicular phase (3.1 x 10(-6) M) and early pregnancy (2.7 x 10(-6) M). ED50 for PGE2 amounted 7.3 x 10(-7) M in the luteal phase and 1.7 x 10(-7) M in early pregnancy. Studies showed the influence of the estrous cycle and early pregnancy on OA branches sensitivity to the contractile effect of PGF2alpha and the lack of this effect on UA branches, and the influence of the estrous cycle on UA and OA branch contraction in response to PGE2.

11Beta-hydroxysteroid dehydrogenase (HSD11B) enzymes have important roles in regulating cortisol availability in target tissues. We previously demonstrated that HSD11B1 is expressed and active in bovine endometrium and that cortisol suppresses prostaglandin (PG) F2alpha and PGE2 production in cultured bovine endometrial stromal cells. The present study was conducted to examine whether locally synthesized PGF2alpha and/or PGE2 regulates the enzymatic bioactivity and/or the expression of HSD11B1 in bovine endometrium. The conversion rate of cortisone to cortisol in cultured endometrial stromal cells was significantly stimulated by PGF2alpha (1 and 10 microM). In a dose-dependent manner, PGF2alpha but not PGE2 increased the net conversion of cortisone to cortisol in stromal cells after 4 h of treatment. In addition, the bioactivity of HSD11B1 was significantly inhibited by indomethacin (10 microM). The inhibitory effect of indomethacin on HSD11B1 bioactivity was abolished by PGF2alpha (1 microM) but not by PGE2. Although PGF2alpha (1 microM) did not affect the expression of HSD11B1 mRNA in cultured stromal cells, it significantly stimulated the protein expression of HSD11B1. Cycloheximide, a general translational inhibitor, abolished the stimulatory effects of PGF2alpha on HSD11B1 protein expression in endometrial stromal cells, indicating that PGF2alpha increases HSD11B1 protein expression by stimulating a posttranscriptional process rather than a transcriptional mechanism. These results demonstrate that PGF2alpha but not PGE2 increases HSD11B1 bioactivity and protein expression by stimulating a posttranscriptional mechanism in stromal cells and suggest that cortisol has a physiologically relevant role in preventing excessive uterine PG production in nonpregnant bovine endometrium.

Production of prostaglandins (PGs) and expression of their receptors have been demonstrated in bovine corpus luteum (CL). The aim of the present study was to determine whether PGE2 and PGF2alpha have roles in bovine luteal steroidogenic cell (LSC) apoptosis. Cultured bovine LSCs obtained at the midluteal stage (Days 8-12 of the cycle) were treated for 24 h with PGE2 (0.001-1 microM) and PGF2alpha (0.001-1 microM). Prostaglandin E2 (1 microM) and PGF2alpha (1 microM) significantly stimulated progesterone (P4) production and reduced the levels of cell death in the cells cultured with or without tumor necrosis factor alpha (TNF)/interferon gamma (IFNG), in the presence and absence of FAS ligand (P < 0.05). Furthermore, DNA fragmentation induced by TNF/IFNG was observed to be suppressed by PGE2 and PGF2alpha. Prostaglandin E2 and PGF2alpha also attenuated mRNA expression of caspase 3 and caspase 8, as well as caspase 3 activity (P < 0.05) in TNF/IFNG-treated cells. FAS mRNA and protein expression were decreased only by PGF2alpha (P < 0.05). A specific P4 receptor antagonist (onapristone) attenuated the apoptosis-inhibitory effects of PGE2 and PGF2alpha in the absence of TNF/IFNG (P < 0.05). A PG synthesis inhibitor (indomethacin) reduced cell viability in PGE2- and PGF2alpha-treated cells (P < 0.05). A specific inhibitor of cyclooxygenase (PTGS), PTGS2 (NS-398), also reduced cell viability, whereas an inhibitor of PTGS1 (FR122047) did not affect it. The overall results suggest that PGE2 and PGF2alpha locally play luteoprotective roles in bovine CL by suppressing apoptosis of LSCs.

Prostaglandins (PG) E2, PGF2alpha and thromboxane (TX) mediate uterine contractility by targeting prostonoid EP, FP and TP receptors respectively. The aim of this study was to elucidate the function of these receptors in isolated human myometrium taken at term gestation prior to and following labour onset. Lower segment myometrial strips were immersed in organ baths in oxygenated Krebs' solution at 37 degrees C and connected to isometric force transducers. After equilibration, spontaneous activity and concentration responses to PGE2, PGF2alpha and U46619 (a stable TX mimetic) were measured as area under the curve and expressed as a percentage of the final contraction induced by hypotonic shock. Results were expressed as arithmetic means+/-s.e.m. and analysed using two-way ANOVA with Bonferroni's post hoc test. Myometrium excised at late gestation displayed the greatest spontaneous activity compared with the tissues taken during labour (P<0.001). Excitation evoked by PGF2alpha (P<0.01) and PGE2 at 10(-5) mol/l were attenuated after labour onset. U46619 consistently stimulated concentration-dependent contractions (P<0.001) and selective antagonists confirmed TP-mediated effects. The maintained responses to TX indicate crucial roles for TP receptors in the muscular tonus of the parturient uterus. This receptor and its secondary messenger system represent effective myometrial targets for tocolytic agents in both pregnancy and labour-associated disorders.

Increased expression of cyclooxygenase-2 (COX-2) and subsequent prostaglandin production is an important event in several human malignancies, including colorectal cancer. COX-2 mediated prostanoid synthesis has been shown to play a key role in tumor progression with prostaglandin E(2) (PGE(2)) being shown to promote tumor growth, invasion and angiogenesis. The role of the other prostaglandins produced by COX-2 in tumors remains poorly understood. We have shown that colorectal tumor cells produce prostaglandin F(2alpha) (PGF(2alpha)) and provide evidence that PGF(2alpha) may play an important role in colorectal tumorigenesis. Our data show that PGF(2alpha) is secreted by both colorectal adenoma and carcinoma-derived cell lines at levels in excess of those detected for PGE(2). These cell lines were also found to express the PGF(2alpha) receptor (FP) indicating potential autocrine effects of PGF(2alpha). This finding is further supported by an in vivo immunohistochemical study of FP expression in resected colon tissue. These data show epithelial expression of FP in normal colorectal mucosa and also in colorectal adenomas and carcinomas. We compared the relative abilities of PGF(2alpha) and PGE(2) to induce cell motility in vitro in colorectal tumor cell lines and show the first evidence of prostaglandin-induced cell motility in colorectal adenoma cell lines. PGF(2alpha) induced cell motility with equivalent potency to PGE(2) in all the cell lines tested and was also shown to increase the invasion of carcinoma-derived cells into reconstituted basement membrane. These data show that PGF(2alpha) may play an important role in the malignant progression of colorectal tumors.

Background and Purpose: The prostamides (prostaglandin-ethanolamides) and prostaglandin (PG) glyceryl esters are biosynthesized by COX-2 from the respective endocannabinoids anandamide and 2-arachidonyl glycerol. Agonist studies suggest that their pharmacologies are unique and unrelated to prostanoid receptors. This concept was further investigated using antagonists., Experimental Approach: The isolated feline iris was used as a key preparation, where prostanoid FP receptors and prostamide activity co-exist. Activity at human recombinant FP and other prostanoid receptors was determined using stable transfectants., Key Results: In the feline iris, AGN 204396 produced a rightward shift of the dose-response curves for prostamide F2alpha and the prostamide F2alpha analog bimatoprost but did not block the effects of PGF2alpha and synthetic FP receptor agonists. Studies on human recombinant prostanoid receptors confirmed that AGN 204396 did not behave as a prostanoid FP receptor antagonist. AGN 204396 exhibited no antagonism at DP and EP1-4, but was a highly effective TP receptor antagonist. Contrary to expectation, the FP receptor antagonist AL-8810 efficaciously contracted the cat iris. AGN 204396 did not affect AL-8810 induced contractions, demonstrating that AL-8810 and AGN 204396 are pharmacologically distinct. Unlike AL-8810, the ethylamide derivate of AL-8810 was not an agonist. Al-8810 did not block prostamide F2alpha activity. Finally, AGN 204396 did not block PGE2-glyceryl ester activity., Conclusions and Implications: The ability of AGN 204396 to selectively block prostamide responses suggests the existence of prostamide sensitive receptors as entities distinct from receptors recognizing PGF2alpha and PGE2-glyceryl ester.

Background: Delayed uterine involution has negative effects on the fertility of cows; use of prostaglandin F2alpha alone as a single treatment has not been shown to consistently improve fertility. Combined administration of PGF2alpha and PGE2 increased uterine pressure in healthy cows. We hypothesized, that the combination of both prostaglandins would accelerate uterine involution and have, therefore, a positive effect on fertility variables. In commercial dairy farming, the benefit of a single post partum combined prostaglandin treatment should be demonstrated., Methods: 383 cows from commercial dairy farms were included in this study. Uterine size and secretion were evaluated at treatment 21-35 days post partum and 14 days later. Cows were randomly allocated to one of three treatment groups: PGF2alpha and PGE2, PGF2alpha or placebo. For every animal participating in the study, the following reproduction variables were recorded: Interval from calving to first insemination, days open, number of artificial inseminations (AI) to conception; subsequent treatment of uterus, subsequent treatment of ovaries. Plasma progesterone level at time of treatment was used as a covariable. For continuous measurements, analysis of variance was performed. Fisher's exact test for categorical non-ordered data and exact Kruskal-Wallis test for ordered data were used; pairwise group comparisons with Bonferroni adjustment of significance level were performed., Results: There was no significant difference among treatment groups in uterine size. Furthermore, there was no significant difference among treatments concerning days open, number of AI, and subsequent treatment of uterus and ovaries. Days from calving to first insemination tended to be shorter for cows with low progesterone level given PGF2alpha and PGE2 in combination than for the placebo-group (P = 0.024)., Conclusion: The results of this study indicate that the administration of PGF2alpha or a combination of PGF2alpha and PGE2 21 to 35 days post partum had no beneficial effect upon measured fertility variables. The exception was a tendency for a shorter interval from calving to first insemination after administration of the combination of PGF2alpha and PGE2, as compared to the placebo group. Further research should be done in herds with reduced fertility and/or an increased incidence of postpartum vaginal discharge.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat skeletal muscle injury. However, studies have shown that NSAIDs may be detrimental to the healing process. Mediated by prostaglandin F(2alpha) (PGF(2alpha)) and prostaglandin E(2) (PGE(2)), the cycloxygenase-2 (COX-2) pathway plays an important role in muscle healing. We hypothesize that the COX-2 pathway is important for the fusion of muscle cells and the regeneration of injured muscle. For the in vitro experiments, we isolated myogenic precursor cells from wild-type (Wt) and COX-2 gene-deficient (COX-2(-/-)) mice and examined the effect of PGE(2) and PGF(2alpha) on cell fusion. For the in vivo experiments, we created laceration injury on the tibialis anterior (TA) muscles of Wt and COX-2(-/-) mice. Five and 14 days after injury, we examined the TA muscles histologically and functionally. We found that the secondary fusion between nascent myotubes and myogenic precursor cells isolated from COX-2(-/-) mice was severely compromised compared with that of Wt controls but was restored by the addition of PGF(2alpha) or, to a lesser extent, PGE(2) to the culture. Histological and functional assessments of the TA muscles in COX-2(-/-) mice revealed decreased regeneration relative to that observed in the Wt mice. The findings reported here demonstrate that the COX-2 pathway plays an important role in muscle healing and that prostaglandins are key mediators of the COX-2 pathway. It suggests that the decision to use NSAIDs to treat muscle injuries warrants critical evaluation because NSAIDs might impair muscle healing by inhibiting the fusion of myogenic precursor cells.

Cell transforming activity of palytoxin, a non-TPA type tumor-promoter, was investigated with the two-stage transformation assay using Balb/c 3T3 cells. Palytoxin showed potent promoting activity; treatment at 1.9 pM or more increased the number of transformed foci after initiation by 3-methylcholanthrene (MCA). Determination of prostaglandin (PG) E2 and PGF(2alpha) concentrations in the culture medium revealed that palytoxin (1.9-3.7 pM for 24 h) stimulated the production of PG in Balb/c 3T3 cells (the concentration reached 3-4 microM), and treatment with PGE2 or PGF(2alpha) itself increased the number of transformed foci of Balb/c 3T3 cells after initiation by MCA. Neither palytoxin nor PGs showed initiating activity. Indomethacin suppressed the promoting activity of palytoxin, but not that of PGE2 and PGF(2alpha). Interestingly, concomitant treatment with PGE2 or PGF(2alpha) in addition to indomethacin markedly reversed the suppressive effect of indomethacin. These findings indicated that the in vitro transformation model could reproduce experiments that have been performed in animal models regarding the inhibitory effect of indomethacin on carcinogenic responses and reversal of indomethacin's effect by exogenous prostaglandin and, therefore, may provide insight into molecular modes of action of palytoxin. In the present study, palytoxin also induced prostaglandin synthesis, and therefore, the Balb/c 3T3 cell model should provide insight into the molecular mechanism by which palytoxin regulates prostaglandin biosynthesis.

Coordination of intercellular Ca2+ signals is important for certain hepatic functions including biliary flow and glucose output. Prostaglandins, such as PGF2alpha and PGE2, may modify these hepatocyte functions by inducing Ca2+ increase, but very little is known about the organization of the Ca2+ signals induced by these agonists. We studied Ca2+ signals induced by PGF2alpha and PGE2 in fura-2 AM-loaded hepatocyte doublets. Even though both prostaglandins induced Ca2+ oscillations, neither PGF2alpha nor PGE2 induced coordinated Ca2+ oscillations in hepatocyte doublets. Gap junction permeability (GJP), assessed by fluorescence recovery after photobleaching, showed that this absence of coordination was not related to a defect in GJP. Inositol (1,4,5)trisphosphate [Ins(1,4,5)P3] assays and the increase in Ins(1,4,5)P3 receptor sensitivity to Ins(1,4,5)P3 observed in response to thimerosal suggested that the absence of coordination was a consequence of the very small quantity of Ins(1,4,5)P3 formed by these prostaglandins. Furthermore, when PGE2 and PGF2alpha were added just before norepinephrine, they favored the coordination of Ca2+ signals induced by norepinephrine. However, GJP between hepatocyte doublets was strongly inhibited by prolonged (>or=2 h) treatment with PGF2alpha, thereby preventing the coordination of Ca2+ oscillations induced by norepinephrine in these cells. Thus, depending on the time window, prostaglandins, specially PGF2alpha, may enhance or diminish the propagation of Ca2+ signals. They may therefore contribute to the fine tuning of Ca2+ wave-dependent functions, such as nerve stimulation, hormonal regulation of liver metabolism, or bile secretion, in both normal and pathogenic conditions.

To investigate whether selective COX 2 inhibitors (celecoxib, rofecoxib) would play a role in a model of leukocyte migration in rats. Bacterial endotoxin (Escherichia coli LPS) was intraperitoneally injected at time zero in rats that were previously treated with unspecific and selective cyclooxygenase inhibitors. LPS induced a dose and time-dependent increase in leukocyte number, which was predominantly related to the presence of PMN neutrophils. Only rats treated with selective COX 2 inhibitors and indomethacin showed a significant reduction in leukocyte numbers following LPS administration. Prostaglandins E(2) and F(2alpha) were injected into the peritoneum and the chemoatractant effect was studied. Only PGF(2alpha) was able to induce neutrophil increase following injection. Intraperitoneal reposition of PGF(2alpha) restored the abrogated leukocyte response to LPS, shown by rats pretreated with rofecoxib. It can be concluded that COX 2, through PGF(2alpha) release, is the isoform responsible for neutrophil recruitment in the rat model of LPS-induced inflammation.

Nitric oxide (NO) has emerged as one of several important intraovarian regulatory factors. Although the importance of NO has been demonstrated during gestation, its role in oocyte meiotic maturation (MM) is incompletely clear. In this context, the effects of nitric oxide synthase (NOS) blocker (N-omega-mono-methyl L-arginine, L-NMMA), NO donor (sodium nitroprusside, Na-NP), and exogenous prostaglandins (PGs) F2alpha and E2 on the MM of oocytes in mice have been studied. The exogenous PGs in a dose of 3.00 microg/kg inhibited the MM of murine oocytes. The effect of L-NMMA on the MM of oocytes was studied for the first time depending on the size of a follicle from which they were isolated. The maximum inhibition was observed for oocytes isolated from small follicles. Na-NP induced an increase in the number of oocytes from small (p < 0.01) and medium (p < 0.05) follicles, capable of forming polar bodies after a 20-h cultivation. The introduction of PG F2alpha to the test animals pretreated with L-NMMA potentiated the inhibition of MM. The NO donor decreased the inhibiting effect of PG F2alpha on the MM of oocytes isolated from small (p < 0.05) and medium (p < 0.05) follicles. The results confirm that NO/NOS ovarian system is involved into the mechanism of the PG action on the MM of murine oocytes and, probably, that NO is involved into the general mechanism of PG activity. In this case, PG, F2alpha can operate through nongenomic stimulation of membrane/endocellular mediators, where NO also acts as a mediator.

Purpose: To investigate the effects of prostaglandin (PG) E1, E2, F2alpha, and latanoprost acid on the electrically evoked contractile response of isolated rhesus monkey ciliary muscle., Methods: Longitudinal ciliary muscle preparations from rhesus monkeys were mounted in an organ bath, and tension changes were recorded by an isometric transducer. Electrical field stimulation (100 Hz, 0.3 ms, 10 V) was applied through a pair of platinum plate electrodes., Results: The ciliary muscle produced atropine-sensitive excitatory contraction in response to field stimulation. PGE1 and PGE2 (1 microM) attenuated the contraction to levels that were 68% and 65.1%, respectively, of the normal amplitude. However, PGF2alpha and latanoprost acid (1 microM) did not significantly change the response amplitude., Conclusions: Our results indicate that PGF2alpha and latanoprost acid do not interact with the prostanoid receptor involved at the pre- and/or postsynaptic site. Therefore, it is unlikely that the hypotensive action by these agents is due to relaxation of the ciliary muscle.

Background: The prostaglandins (PG) E(2) and PGF(2alpha) are important cytokines in periodontal physiology and pathology. PGE(2) and PGF(2alpha) alter cell function by binding and activating the plasmamembrane G-protein-coupled PG receptors. In this study, we examined the PGE(2) and PGF(2alpha) effects on the immortalized cementoblastic OCCM cells., Methods: Confluent OCCM cells were treated with PGE(2), PGF(2alpha), specific activators/inhibitors of the EP prostanoid receptors, a specific activator of the FP prostanoid receptor, and direct activators/inhibitors of the protein kinase C (PKC) signaling pathway. Mineral nodule formation was assessed by the von Kossa stain., Results: PGE(2) and PGF(2alpha) significantly increased mineralization of OCCM cells. The EP1 and EP3 PG receptor activators 16,16-dimethyl-prostaglandin E(2) and sulprostone, also increased mineralization. In contrast, specific activators of the EP2 or the EP2/EP3/EP4 receptors did not have any effect. Fluprostenol, a specific activator of the FP receptor, significantly increased mineralization of OCCM cells. FP and EP (1 or 3) receptors signal through activation of the protein kinase C (PKC) pathway. Indeed, phorbol 12-myristate 13-acetate (PMA), a direct activator of the PKC pathway, significantly increase OCCM mineralization, while pre-treatment of OCCM cells with the PKC inhibitor GF109203x (bisindolylmaleimide) significantly decreased mineralization., Conclusion: We conclude that PGE(2) and PGF(2alpha) exert an anabolic effect on OCCM mineralization through activation of PKC signaling.

Isoprostanes are not mere bystanders of oxidative injury, but possess potent biological activity and may thus contribute to the pathophysiology of various disorders associated with an increase in free radical formation. 15-F2t-IsoP (8-iso-prostaglandin F2) and 15-E2t-IsoP (8-iso-prostaglandin E2), two of the most abundant isoprostanes, are potent vasoconstrictors in various vascular beds, including the kidney. Since their discovery, numerous studies have aimed to define the receptors through which isoprostanes exert their effects. Whether the thromboxane receptor and/or other prostaglandin receptors mediate the actions of isoprostanes, or whether these compounds interact with their own unique receptors, remains to be clarified. Regardless of their exact mode of action, isoprostanes are being implicated in the pathophysiology of a variety of diseases, and their discovery might give rise to novel therapies for these diseases. Here we describe early studies that defined the vasoactive properties of isoprostanes in the kidney, and subsequent discoveries relating to their renal actions and pathophysiologic significance.

FP prostanoid receptors are G-protein-coupled receptors that consist of two isoforms named FPA and FPB. Both isoforms activate inositol phosphate second messenger signaling pathways by their endogenous ligand prostaglandin F2alpha (PGF2alpha). Previously we have shown that both isoforms undergo Rho-mediated cell rounding following treatment with PGF2alpha. Following the removal of PGF2alpha, however, FPA-expressing cells return to their original morphology, whereas FPB-expressing cells do not. It was also found that PGF2alpha-could activate T-cell factor (Tcf)/beta-catenin signaling in cells expressing the FPB isoform but not in cells expressing the FPA isoform. We now show that prostaglandin E2 (PGE2) can induce cell rounding and stimulate the formation of inositol phosphates to the same extent as PGF2alpha in cells expressing either the FPA or FPB isoforms. However, PGE2 has much lower efficacy as compared with PGF2alpha for the activation of Tcf/beta-catenin signaling in FPB-expressing cells, and the cell rounding is reversible. Interestingly, pretreatment of FPB-expressing cells with PGE2-attenuated PGF2alpha-stimulated Tcf/beta-catenin signaling in a dose-dependent manner while having no effect on PGF2alpha-stimulated inositol phosphates formation. Thus, the ratio of endogenous PGE2 and PGF2alpha has the potential to selectively regulate one signaling pathway over another. This represents a novel mechanism for the regulation of cell signaling that is distinct from regulation occurring at the level of the receptor and its effector pathways.

The present study was undertaken to determine whether 8-iso-prostaglandin E2 and 8-iso-prostaglandin F(2alpha) posses contractile action on human umbilical vein and to evaluate the possible involvement of prostanoid TP receptors in this effect. Human umbilical vein rings were mounted in organ baths and concentration-response curves to 8-iso-prostaglandin E2 or 8-iso-prostaglandin F(2alpha) were constructed. Both isoprostanes evoked concentration-dependent contraction. 8-iso-prostaglandin E2 (pEC50=6.90+/-0.03) was significantly more potent than 8-iso-prostaglandin F(2alpha) (pEC50=6.10+/-0.04). However, both isoprostanes were equieffective. The prostanoid TP receptor antagonists, ICI-192,605 (4-(Z)-6-(2-o-Chlorophenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl)hexenoic acid) and SQ-29548 (7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-[1S(1alpha,2alpha(Z),3alpha,4alpha)]-5-Heptenoic acid) produced a competitive rightward shift of 8-iso-prostaglandin E2 concentration-response curves with pKB values of 8.91+/-0.04 and 8.07+/-0.07, respectively. When ICI-192,605 (1 nM) and SQ-29548 (10 nM) were evaluated against 8-iso-prostaglandin F(2alpha) they produced a parallel rightward displacement of 8-iso-prostaglandin F(2alpha) concentration-response curves without affecting the maximum responses giving pA2 values of 9.02+/-0.12 and 8.26+/-0.13, respectively. In conclusion, the present study describes for the first time the vasoconstrictor action of 8-iso-prostaglandin E2 and 8-iso-prostaglandin F(2alpha) in human umbilical vein. Furthermore, the affinity values obtained with ICI-192,605 and SQ-29548 provide strong pharmacological evidence of prostanoid TP receptors involvement in this effect.

Prostaglandins (PG) are key mediators of diverse functions in the skin and several reports suggest that PG mediate post-inflammatory pigmentary changes through modulation of melanocyte dendricity and melanin synthesis. The proteinase-activated receptor 2 (PAR-2) is important for skin pigmentation because activation of keratinocyte PAR-2 stimulates uptake of melanosomes through phagocytosis in a Rho-dependent manner. In this report, we show that activation of keratinocyte PAR-2 stimulates release of PGE(2) and PGF(2alpha) and that PGE(2) and PGF(2alpha) act as paracrine factors that stimulate melanocyte dendricity. We characterized the expression of the EP and FP receptors in human melanocytes and show that human melanocytes express EP1 and EP3, and the FP receptor, but not EP2 and EP4. Treatment of melanocytes with EP1 and EP3 receptor agonists resulted in increased melanocyte dendricity, indicating that both EP1 and EP3 receptor signaling contribute to PGE(2)-mediated melanocyte dendricity. Certain EP3 receptor subtypes have been shown to increase adenosine 3',5'-cyclic monophosphate (cAMP) through coupling to Gs, whereas EP1 is known to couple to Gq to activate phospholipase C with elevation in Ca(2+). The cAMP/protein kinase A system is known to modulate melanocyte dendrite formation through modulation of Rac and Rho activity. Neither PGF(2alpha) or PGE(2) elevated cAMP in human melanocytes showing that dendricity observed in response to PGE(2) and PGF(2alpha) is cAMP-independent. Our data suggest that PAR-2 mediates cutaneous pigmentation both through increased uptake of melanosomes by keratinocytes, as well as by release of PGE(2) and PGF(2alpha) that stimulate melanocyte dendricity through EP1, EP3, and FP receptors.

The effects of nitric oxide (NO) synthase (NOS) blocker (L-NMMA), NO donor (sodium nitroprusside, Na-NP), and exogenous prostaglandins (PGs) F2 alpha and E2 on the meiotic maturation (MM) of murine oocytes were studied. The exogenous PGs in a dose of 3.00 micrograms/kg inhibited the MM of oocytes. The effect of L-NMMA on the MM of oocytes was studied for the first time depending on the size of a follicle from which they were isolated. The maximum inhibition was observed for oocytes isolated from small follicles. Na-NP induced an increase in the number of oocytes from small and medium follicles, capable of forming polar bodies after a 20-h cultivation. The introduction of PG F2 alpha to the test animals pretreated with L-NMMA potentiated the inhibition of MM. The NO donor decreased the inhibiting effect of PG F2 alpha on the MM of oocytes isolated from small and medium follicles. The results confirm that NO/NOS ovarian system is involved into the mechanism of the PG action on the MM of murine oocytes and, probably, in the general mechanism of PG activity.

Objective: To determine the in vitro effect of prostaglandin (PG) E2, PGF2alpha, and the nonsteroidal anti-inflammatory drugs (NSAIDs) indomethacin, ketoprofen, and nabumetone on the contractile strength of the circular smooth muscle layer of the third compartment of the stomach of llamas., Sample Population: Specimens of the third compartment obtained from 5 healthy adult llamas., Procedure: Full-thickness tissue samples were collected from the third compartment immediately after euthanasia. Specimens were cut into strips oriented along the circular muscle layer and mounted in a tissue bath system. Incremental amounts of ketoprofen, nabumetone, indomethacin, PGE2, and PGF2alpha were added, and contractile strength (amplitude of contractions) was recorded., Results: Generally, PGE2 reduced contractile strength of the circular smooth layer of the third compartment, whereas PGF2alpha, increased the strength of contractions. The activity of the NSAIDs was generally excitatory in a concentration-dependent manner, although significant changes were induced only by administration of indomethacin., Conclusions and Clinical Relevance: On isolated smooth muscle strips of the third compartment of llamas, exogenous PGE2 and PGF2alpha had a variable effect on contractile strength. Administration of the NSAIDs did not inhibit contractility and would not be likely to induce stasis of the third compartment in the absence of an underlying disease process.

The pharmacological properties of [(3)H]-prostaglandin E(2) ([(3)H]-PGE(2)) binding to washed homogenates of hamster uterus were determined. Scatchard analysis of competition data yielded dissociation constants (K(d)s) of 30.9 +/- 5.6 nM (n = 3) and apparent receptor density (B(max)) of 25.25 +/- 1.89 pmol g(-1) wet weight tissue (74 +/- 8% specific binding). Competition studies yielded the following affinity parameters (K(i)) for various prostanoids: GR63799X = 13 4 nM; PGE(2) = 17 +/- 3 nM; sulprostone = 64 +/- 5 nM; enprostil = 67 +/- 3 nM; misoprostol = 124 +/- 15 nM; cloprostenol = 187 +/- 33 nM; carba-prostacyclin = 260 +/- 167 nM; iloprost = 555 +/- 162 nM; PGF(2 alpha) = 767 +/- 73 nM; PGD(2) > 3560 nM; fluprostenol = 11 790 +/- 2776 nM; RS93520 = 21 558 +/- 14 228 nM. These data closely matched the pharmacological profile of previously described EP(3) receptors such as in bovine corpus luteum (BCLM) and the cloned mammalian EP(3) receptors. The high correlation between the current hamster uterus pharmacology data vs the EP(3) receptor binding in BCLM (r = 0.94; P < 0.0001), vs cloned human EP(3) receptor (r = 0.94, P < 0.0001), vs the cloned mouse EP(3) receptor binding (r = 0.78; P < 0.002), vs cloned rat EP(3) receptor (r = 0.9, P < 0.0004), and vs EP(3) receptor-mediated functional responses (r = 0.72, P < 0.02) substantiated the conclusion that the hamster uterus contains EP(3) receptor binding sites.

In the present experiment, we examined the effect of 8-iso-prostaglandin E(2) and 8-iso-prostaglandin F(2 alpha) on the release of noradrenaline from the isolated rat stomach. The postganglionic sympathetic nerves were electrically stimulated twice at 1 Hz for 1 min and test reagents were added during the second stimulation. 8-Iso-prostaglandin E(2) (10(-8)-10(-6) M) and 8-iso-prostaglandin F(2 alpha) (10(-7)-10(-5) M) dose-dependently reduced the evoked noradrenaline release, and these inhibitory potencies were as follows: 8-iso-prostaglandin E(2)>8-iso-prostaglandin F(2 alpha). The inhibitory effect of 8-iso-prostaglandin F(2 alpha), but not 8-iso-prostaglandin E(2), was abolished by 10(-6) M SQ-29548 ([1S-[1 alpha,2 alpha(Z),3 alpha,4 alpha]]-7-[3-[[2-[(phenylamino)carbonyl]hydrazino] methyl]-7-oxabicyclo[2,2,1]hept-2-yl]-5-heptenoic acid) (a prostanoid TP receptor antagonist). On the other hand, the inhibitory effect of 8-iso-prostaglandin E(2) was abolished by 10(-5) M AH-6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid) (a prostanoid EP receptor antagonist), which also attenuated the inhibitory effects of ONO-AE-248 (16S-9-deoxy-9 beta-chloro-15-deoxy-16-hydroxy-17,17-trimethylene 19, 20-didehydro prostaglandin F(2)) (a selective EP(3) receptor agonist) on the evoked release of noradrenaline. The inhibitory effect of 8-iso-prostaglandin F(2 alpha), but not 8-iso-prostaglandin E(2), was abolished by pertussis toxin. These results suggest that 8-iso-prostaglandin F(2 alpha) inhibits noradrenaline release through TP receptors, whereas 8-iso-prostaglandin E(2) seems to inhibit noradrenaline release through EP(3) receptors, located on the gastric sympathetic nerve terminals in rats.

Prostaglandins (PG) mediate IL-1beta regulation of several interleukin mRNAs in progenitor Leydig cells. PGE(2) and PGF(2alpha) potently reverse indomethacin (INDO; a cyclooxygenase inhibitor) inhibition of IL-1beta autoinduction. IL-1beta increases PGE(2) and PGF(2alpha) production. To determine the PG receptors involved in this regulation, this study established by RT-PCR and Western analyses which specific receptors for PGE(2) (EP receptors) and PGF(2alpha) (FP receptors) are expressed in progenitors. Pharmacological characterization of receptors involved in PGE(2) and PGF(2alpha) regulation of IL-1beta mRNA levels was ascertained using real-time PCR analyses. FP, EP(1), EP(2), and EP(4) receptor mRNAs and proteins, and an EP(3) receptor subtype were detected. IL-1beta treatment (24-h) significantly decreased EP(1) receptor levels; INDO abrogated this down-regulation. FP, EP(2), and EP(4) receptor levels increased after IL-1beta and IL-1beta + INDO. A selective FP agonist, cloprostenol (0.1 micro M), and PGF(2alpha) (10 micro M) had similar effects on IL-1beta mRNA levels in progenitors treated with IL-1beta + INDO. None of the EP(2)/EP(4) agonists [butaprost, misoprostol, or 11-deoxy PGE(1) (10 micro M)] affected IL-1beta mRNA levels. In contrast, EP(1)/EP(3) agonists (17-phenyl trinor PGE(2) and sulprostone) increased IL-1beta mRNAs in a dose-dependent manner. EP(1) receptor subtype-selective antagonist, SC-51322, blocked IL-1beta-induced and [IL-1beta + INDO + 17-phenyl trinor PGE(2)]-induced increases in IL-1beta mRNAs. Taken together, our data demonstrate that FP and EP(1) receptors mediate PGF(2alpha) and PGE(2) induction of progenitor IL-1beta expression.

Oxytocin and prostaglandins (PGs) are hormones involved in labor and are used clinically for its induction. In this study the effect of oxytocin, PGF(2alpha), and PGE(2) on Humour immunodeficiency virus-1 production in acutely and persistently infected cells was measured. No significant effect on p24 antigen production was found with oxytocin or PGs, except for a transient decrease in persistently infected cells treated with 1 micro M PGF(2alpha). These results showed that oxytocin and PGs could be used clinically for labor induction without any direct enhancement in viral production. Besides, the results with PGF(2alpha) at the highest concentration studied may indicate a pharmacological effect.

Background and Purpose: Free radical-induced peroxidation is an important factor in the genesis of hypoxic-ischemic encephalopathy, including that of the preterm infant. Isoprostanes are major peroxidation products. Since microvascular dysfunction seems to contribute to ischemic encephalopathies, we studied the cytotoxicity of 8-iso-prostaglandin F2alpha (PGF2alpha) on cerebral microvascular cells., Methods: Microvascular endothelial, astroglial, and smooth muscle cells from newborn brain were cultured. The cytotoxicity of 8-iso-PGF2alpha on these cells was determined by MTT assays and lactate dehydrogenase (LDH) release, propidium iodide incorporation, and DNA fragmentation (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling [TUNEL]). In addition, effects of intraventricular injections of 8-iso-PGF2alpha and possible involvement of thromboxane in 8-iso-PGF2alpha-induced cytotoxicity were determined., Results: 8-Iso-PGF2alpha induced time- and concentration-dependent endothelial cell death (EC50=0.1 nmol/L) but exerted little effect on smooth muscle and astroglial cells; endothelial cell death seemed mostly of oncotic nature (propidium iodide incorporation and LDH release). Cell death was associated with increased endothelial thromboxane A2 (TXA2) formation and was prevented by TXA2 synthase inhibitors (CGS12970 and U63557A); TXA2 mimetics U46619 and I-BOP also caused endothelial cell death. Intraventricular injection of 8-iso-PGF2alpha induced periventricular damage, which was attenuated by CGS12970 pretreatment., Conclusions: These data disclose a novel action of 8-iso-PGF2alpha involving TXA2 in oxidant stress-induced cerebral microvascular injury and brain damage.

Little is known of the cardiovascular functions of prostaglandins in non-mammalian vertebrates. There are indications that prostaglandins may have a function in haemostasis by constricting blood vessels in filament arteries in the fish gill after injury. Our aim was to examine the cardiovascular effect of the prostaglandins F(2 alpha) (PGF(2 alpha)) and E(2) (PGE(2)) with emphasis on branchial circulation. Intra-arterial injections of PGF(2 alpha) (10, 40, 160, 400 nmol kg(-1)) in cod caused a dose-dependent increase in ventral aortic blood pressure, a reduction in cardiac output, and an increase in gill vascular resistance. A contraction of filament arteries was observed with in vivo microscopy only seconds after injection. PGF(2 alpha) may therefore possibly be involved in a haemostatic vasoconstriction. In contrast, the most significant effects of PGE(2) appeared to be on the heart. PGE(2) also reduced dorsal aortic blood pressure.

The effects of intrathecal (i.t.) administration of prostaglandin E2 (PGE2) and prostaglandin F2 (PGF2) on behavioral and spinal neuronal responses to mechanical and thermal stimuli were examined in rats. i.t. Administration of either PGE2 (1-100 nmol) or PGF2 (1-100 nmol) produced a robust, dose-dependent mechanical hyperalgesia, but only a weak thermal hyperalgesia and touch-evoked allodynia. Spinal administration of either PGE2 (100 pmol-100 nmol) or PGF2 (1-100 nmol) produced dose-dependent increases in responses of nociceptive specific (NS) neurons to mechanical stimuli, but only modest increases in wide dynamic range (WDR) neurons to mechanical stimuli. Spinal administration of PGE2 produced a bi-directional, dose-response effect on thermally-evoked responses of both WDR and NS neurons when prostaglandin-induced changes in background discharges were controlled for. Thermally evoked responses of WDR and NS neurons were decreased at lesser doses of PGE2, but this trend reversed with greater doses, such that responses of WDR neurons were significantly increased at the greatest dose tested at some test temperatures. PGF2 generally produced non-significant increases in thermally evoked neuronal responses, and this trend occurred primarily in WDR neurons. Both PGE2 and PGF2 produced increases in background discharges of WDR and NS neurons, although this effect was most consistently observed with WDR neurons and PGE2. These behavioral and electrophysiological data suggest that mechanical hyperalgesia induced by spinal administration of PGE2 and PGF2 is mediated mainly by changes in NS neurons. The weak thermal hyperalgesia may reflect changes in WDR neurons.

Objective: The uterus is a target for prostaglandins, especially at the end of gestation. Whether potassium channels are involved in the effect of prostaglandins is not clear. The aim of this study was to find out., Study Design: Concentration-response relationships to prostaglandins (prostaglandin F2alpha, prostaglandin E2, and prostaglandin I2 [carbacyclin]; 10(-10) mol/L-10(-4) mol/L) were studied in isolated uterine rings from mid pregnancy (day 14) and late pregnancy (day 21) rats (Krebs solution, 5% CO2 in air, 37 degrees C; pH, 7.4). Rings were incubated for 30 minutes with either solvent or adenosine triphosphate-sensitive potassium channel inhibitor or opener glibenclamide and levcromakalim or with calcium-sensitive potassium channel inhibitor or opener NS1619 and iberiotoxin, respectively. The changes in integral activity were compared after each concentration of the agent and were expressed as a percent of the basal integral activity., Results: The increases in spontaneous contractile activity induced by prostaglandin E2 and carbacyclin, but not prostaglandin F2alpha, were statistically significantly higher in tissues from late pregnancy versus mid pregnancy rats and were not affected by any of the K-channel openers or inhibitors., Conclusion: Adenosine triphosphate-sensitive and calcium-sensitive potassium channels are not involved in the effect of prostaglandin F2alpha, prostaglandin E2, and prostaglandin I2 on pregnant rat uterus.

Background: Latanoprost is a prostaglandin (PG)F2alpha analogue widely recognized in the treatment of glaucoma. To investigate the action of this drug on the ocular circulation, we have studied its effects on isolated rabbit ciliary artery. The data obtained on this drug are compared with the data from PGE2 and PGF2alpha., Methods: Under the microscope, ciliary artery specimens were prepared from rabbit eyes and mounted in a myograph system. The effects of latanoprost, PGE2, and PGF2alpha on the isolated rabbit ciliary artery were investigated in vitro using isometric tension recording methods., Results: Exogenously applied PGF2alpha, but not latanoprost, evoked contraction in the rabbit ciliary artery. After precontraction with excess-[K]0 solution, latanoprost evoked relaxation dose-dependently. Latanoprost at a concentration of 100 microM induced maximum relaxation, which was not blocked by 10 microM L-nitro-L-arginine methylester (L-NAME), 1 microM 8-37 calcitonin gene-related peptide (CGRP) or 10 microM indomethacin. Moreover, latanoprost induced relaxation even in preparations without endothelium. The maximum relaxation obtained with PGE2 was somewhat less than 50% of that with latanoprost., Conclusions: These results indicate that latanoprost and PGE2 relaxed rabbit ciliary artery to different degrees. The relaxation provoked by latanoprost was not dependent on endothelium and was not caused by intrinsic PG, CGRP or nitric oxide. The mechanism of this relaxation is not yet clear.

The objective of these studies was to characterize the effects of a broad range of prostanoid agonists upon the stimulation of cAMP production in National Cancer Bank (NCB-20; mouse neuroblastoma/hamster brain hybridoma) cells. The pharmacology of these functional responses in NCB-20 cells was compared with that of the classic endogenous IP receptor present on human platelets using [3H]-iloprost binding techniques. In both assay systems, agonists from the IP prostanoid class exhibited the highest affinities and functional potencies. Specific prostanoids exhibited the following rank order of potency (EC50 +/- SEM) in stimulating cAMP production in the NCB-20 cells: carbaprostacyclin (4.3 +/- 0.9 nM) = PGI2 (6.6 +/-1.5 nM) > iloprost (75+/-13 nM) > 11-deoxy PGE, (378+/-138 nM) > misoprostol (1,243+/-48) > PGE2 (3020+/-700 nM) > ZK-118182 (7265+/-455 nM). Iloprost wasthe most potent compound in the human platelet binding assay while prostanoidsfromthe DPand EP receptor classes showed modest affinity. These studies provide functional and binding information for a broad range of both natural and synthetic prostanoid receptor ligands at the endogenous IP receptor in two different cell types.

Isoprostanes (IsoP) are formed by free radical catalyzed peroxidation of arachidonic acid independent of the cyclooxygenase enzyme. In the present study, we examined the effect of IsoP on norepinephrine (NE) release from the bovine isolated iris. Furthermore, we studied the role of IsoP's in hydrogen peroxide (H2O2)-induced enhancement of NE release from this tissue. Isolated bovine irides were prepared for studies of [3H]NE release using the superfusion method. Release of [3H]NE was induced via electrical field stimulation. Both 8-iso-prostaglandin E2 (E2-IsoP) and 8-iso-prostaglandin F2 alpha (F2-IsoP) produced a concentration-related enhancement of field-stimulated [3H]NE release from isolated bovine irides, an effect that was mimicked by the thromboxane (Tx) receptor agonist, U46619 and by H2O2. The Tx-receptor antagonist, SQ 29548 inhibited responses to E2-IsoP (10 microM) with an IC50 of 370 +/- 50 nM. SQ 29548 (10 microM) also blocked the enhancement of electrically-evoked [3H]NE release induced by U46619 (10 microM) but not that caused by H2O2 (300 microM). The Tx synthetase inhibitor, carboxyheptylimidazole (10 microM) prevented the stimulatory effect of E2-IsoP on evoked [3H]NE release without affecting responses induced by H2O2. We conclude that IsoP's can enhance sympathetic neurotransmission in the bovine isolated iris, an effect that can be blocked by a Tx-receptor antagonist. Furthermore, endogenously produced Tx's mediate the stimulatory effect of IsoP's on NE release. However, endogenously generated IsoP's or Tx's are not involved in H2O2-induced potentiation of sympathetic neurotransmission.

Unlabelled: Although intradermal injection of capsaicin produces acute pain and secondary hyperalgesia, long-term topical application of capsaicin cream has been used as a medication for pain relief in various pain conditions. We previously reported that intrathecal administration of prostaglandin (PG) E(2) and PGF(2alpha) into mice induced touch-evoked pain (allodynia) through capsaicin-sensitive and capsaicin-insensitive afferent fibers, respectively. To clarify the mechanism of an analgesic effect by capsaicin cream, here we applied it to the tail and hind paws of mice and investigated its effects on PGE(2)- and PGF(2alpha)-induced allodynia. Twenty-four-hour pretreatment of mice with 0.025% or 0.05% capsaicin cream markedly alleviated allodynia induced by PGE(2), but not by PGF(2alpha). These results suggest that the topical application of capsaicin cream modulates capsaicin-sensitive afferents and ameliorates allodynia evoked by PGE(2) at the spinal level., Implications: Topical application of capsaicin cream alleviates touch-evoked pain induced by the intrathecal administration of prostaglandin E(2). This study may provide a rationale for the use of capsaicin cream as a therapeutic drug for pain relief.

Purpose: To investigate the effect of prostaglandins (PGs) on the permeability of human sclera in vitro., Methods: Twenty-three pairs of human eye bank eyes were studied. Circular pieces of sclera were cultured in low-serum DMEM/F-12 media. Scleral hydration was assessed by measuring wet and dry weight of scleral cultures incubated with medium for 3 days and with Hanks' buffered saline solution (HBSS) for 4 hours. To assess scleral permeability, organ-cultured scleral tissues were exposed to 100 to 500 nM PGF(2alpha), 17-phenyltrinor PGF(2alpha), or PhXA85 (the active form of latanoprost) for 1, 2, and 3 days. Scleral permeability was measured using a two-chamber Ussing apparatus and rhodamine-dextran polymers dissolved in HBSS (MW = 10,000, 40,000, and 70,000). The movement of each rhodamine-dextran across the cultured sclera was measured using a spectrofluorometer. To understand the biological basis of the permeability change, the media were collected from the treated cultures, and the concentration of MMP-1, 2, and 3 was measured using an enzyme-linked immunosorbent assay., Results: There was no difference in scleral hydration among fresh sclera and sclera incubated with medium for 3 days, with HBSS for 4 hours, or with medium for 3 days followed by HBSS for 4 hours. Compared to tracer movement across untreated scleral cultures (1.5 x 10(-6) cm/sec for 10 kDa dextran, 0.7 x 10(-6) cm/sec for 40 kDa dextran, and 0.4 x 10(-6) cm/sec for 70 kDa dextran), exposure to PGF(2alpha), 17-phenyltrinor PGF(2alpha), or PhXA85 each increased scleral permeability in a dose- and time-dependent manner. Increases in permeability were greater with the10 kDa dextran than with the 40 or 70 kDa dextran. The magnitude of these effects was greatest with exposure to PhXA85 and similar with exposure to PGF(2alpha) or 17-phenyltrinor-PGF(2alpha). MMP expression also was significantly increased after PG exposure. These increases were generally time and dose dependent and greater with MMP-2 and -3 than with MMP-1., Conclusions: There is increased permeability of human sclera exposed to various PGs in organ culture. This increased permeability is accompanied by increased expression of MMPS:

Two experiments were conducted to determine the luteotropin of pregnancy in sheep and to examine autocrine and paracrine roles of progesterone and estradiol-17 beta on progesterone secretion by the ovine corpus luteum (CL). Secretion of progesterone per unit mass by day-8 or day-11 CL of the estrous cycle was similar to day-90 CL of pregnancy (P > or = 0.05). In experiment 1, secretion of progesterone in vitro by slices of CL from ewes on day-8 of the estrous cycle was increased (P < or = 0.05) by LH or PGE2. Secretion of progesterone in vitro by CL slices from day-90 pregnant ewes was not affected by LH (P > or = 0.05) while PGE2 increased (P < or = 0.05) secretion of progesterone. Day 8 ovine CL of the estrous cycle did not secrete (P > or = 0.05) detectable quantities of PGF2alpha or PGE while day-90 ovine CL of pregnancy secreted PGE (P < or = 0.05) but not PGF2alpha. Secretion of progesterone and PGE in vitro by day-90 CL of pregnancy was decreased (P < or = 0.05) by indomethacin. The addition of PGE2, but not LH, in combination with indomethacin overcame the decreases in progesterone by indomethacin (P < or = 0.05). In experiment 2, secretion of progesterone in vitro by day-11 CL of the estrous cycle was increased at 4-h (P < or = 0.05) in the absence of treatments. Both day-11 CL of the estrous cycle and day-90 CL of pregnancy secreted detectable quantities of PGE and PGF2alpha (P < or = 0.05). In experiment 1, PGF2alpha secretion by day-8 CL of the estrous cycle and day-90 ovine CL of pregnancy was undetectable, but was detectable in experiment 2 by day-90 CL. Day 90 ovine CL of pregnancy also secreted more PGE than day-11 CL of the estrous cycle (P < or = 0.05), whereas day-8 CL of the estrous cycle did not secrete detectable quantities of PGE (P > or = 0.05). Trilostane, mifepristone, or MER-25 did not affect secretion of progesterone, PGE, or PGF2alpha by day- 11 CL of the estrous cycle or day-90 CL of pregnancy (P > or = 0.05). It is concluded that PGE2, not LH, is the luteotropin at day-90 of pregnancy in sheep and that progesterone does not modify the response to luteotropins. Thus, we found no evidence for an autocrine or paracrine role for progesterone or estradiol-17 36 on luteal secretion of progesterone, PGE or PGF2alpha.