Changes in the concentration of prostaglandins in preovulatory human follicles after administration of hCG

Current Insights in Prolactin Signaling and Ovulatory Function

Prolactin (PRL) is a pleiotropic hormone released from lactotrophic cells of the anterior pituitary gland that also originates from extrapituitary sources and plays an important role in regulating lactation in mammals, as well as other actions. Acting in an endocrine and paracrine/autocrine manner, PRL regulates the hypothalamic-pituitary-ovarian axis, thus influencing the maturation of ovarian follicles and ovulation. This review provides a detailed discussion of the current knowledge on the role of PRL in the context of ovulation and ovulatory disorders, particularly with regard to hyperprolactinemia, which is one of the most common causes of infertility in women. Much attention has been given to the PRL structure and the PRL receptor (PRLR), as well as the diverse functions of PRLR signaling under normal and pathological conditions. The hormonal regulation of the menstrual cycle in connection with folliculogenesis and ovulation, as well as the current classifications of ovulation disorders, are also described. Finally, the state of knowledge regarding the importance of TIDA (tuberoinfundibular dopamine), KNDγ (kisspeptin/neurokinin B/dynorphin), and GnRH (gonadotropin-releasing hormone) neurons in PRL- and kisspeptin (KP)-dependent regulation of the hypothalamic-pituitary-gonadal (HPG) axis in women is reviewed. Based on this review, a rationale for influencing PRL signaling pathways in therapeutic activities accompanying ovulation disorders is presented.

A Case-Control Study on the Oxidative Status in Women with Polycystic Ovary Syndrome Treated with Clomiphene Citrate

Background

Polycystic ovary syndrome (PCOS) is associated with infertility or subfertility due to impaired ovulation. Clomiphene citrate is a first-line treatment option for the induction of ovulation in women with PCOS. The study aimed to compare markers of oxidative stress or the total oxidative status (TOS), total antioxidant status (TAS), and levels of paraoxonase-1 (PON-1) before and after day 21 of the menstrual cycle in women with PCOS treated with clomiphene citrate to induce ovulation.

Material/Methods

The study included 75 women who were divided into a control group (n=25) that included healthy untreated women, untreated women with PCOS (n=24) who had spontaneous ovulation, and women with PCOS who were treated with clomiphene citrate for subfertility or infertility (n=26) (the PCOS-CC group). The study group was treated for five days with clomiphene citrate (50 mg/day). Peripheral venous blood was sampled on day 3 and day 21 of the menstrual cycle from women in all three groups, and TAS, TOS, and PON-1 levels were measured.

Results

In all three groups, TAS and PON levels were significantly reduced and TOS values were significantly increased on day 21 of the menstrual cycle. Comparison of TAS, TOS, and PON-1 levels between the three study groups on day 3 and day 21 of the menstrual cycle showed no significant difference (p=0.600, p=0.223, p=0.956, respectively).

Conclusions

This study showed that spontaneous ovulation occurs in association with an oxidative state in healthy women and women with PCOS, and women with PCOS following treatment with clomiphene citrate.

Estrogen promotes luteolysis by redistributing prostaglandin F2α receptors within primate luteal cells

Prostaglandin F2α (PGF2α) has been proposed as a functional luteolysin in primates. However, administration of PGF2α or prostaglandin synthesis inhibitors in vivo both initiate luteolysis. These contradictory findings may reflect changes in PGF2α receptors (PTGFRs) or responsiveness to PGF2α at a critical point during the life span of the corpus luteum. The current study addressed this question using ovarian cells and tissues from female cynomolgus monkeys and luteinizing granulosa cells from healthy women undergoing follicle aspiration. PTGFRs were present in the cytoplasm of monkey granulosa cells, while PTGFRs were localized in the perinuclear region of large, granulosa-derived monkey luteal cells by mid-late luteal phase. A PTGFR agonist decreased progesterone production in luteal cells obtained at mid-late and late luteal phases, but did not decrease progesterone production by granulosa cells or luteal cells from younger corpora lutea. These findings are consistent with a role for perinuclear PTGFRs in functional luteolysis. This concept was explored using human luteinizing granulosa cells maintained in vitro as a model for luteal cell differentiation. In these cells, PTGFRs relocated from the cytoplasm to the perinuclear area in an estrogen- and estrogen receptor-dependent manner. Similar to our findings with monkey luteal cells, human luteinizing granulosa cells with perinuclear PTGFRs responded to a PTGFR agonist with decreased progesterone production. These data support the concept that PTGFR stimulation promotes functional luteolysis only when PTGFRs are located in the perinuclear region. Estrogen receptor-mediated relocation of PTGFRs within luteal cells may be a necessary step in the initiation of luteolysis in primates.

Multiple roles of the prostaglandin D2 signaling pathway in reproduction

Prostaglandins signaling molecules are involved in numerous physiological processes. They are produced by several enzyme-limited reactions upon fatty acids, which are catalyzed by two cyclooxygenases and prostaglandin synthases. In particular, the prostaglandins E2(PGE2), D2(PGD2), and F2(PGF2α) have been shown to be involved in female reproductive mechanisms. Furthermore, widespread expression of lipocalin- and hematopoietic-PGD2synthases in the male reproductive tract supports the purported roles of PGD2in the development of both embryonic and adult testes, sperm maturation, and spermatogenesis. In this review, we summarize the putative roles of PGD2signaling and the roles of both PGD2synthases in testicular formation and function. We review the data reporting the involvement of PGD2signaling in the differentiation of Sertoli and germ cells of the embryonic testis. Furthermore, we discuss the roles of lipocalin-PGD2synthase in steroidogenesis and spermatogenesis, in terms of lipid molecule transport and PGD2production. Finally, we discuss the hypothesis that PGD2signaling may be affected in certain reproductive diseases, such as infertility, cryptorchidism, and testicular cancer.

Divalent cation levels in serum and preovulatory follicular fluid of women undergoing in vitro fertilization embryo transfer

In this controlled clinical study, we determined the serum and follicular fluid concentrations of the biologically active fractions of magnesium (Mg) and calcium (Ca) in 39 women undergoing controlled ovarian stimulation (COH) for in vitro fertilization (IVF) embryo transfer (ET). Serum levels of ionized Ca (Ca2+) and ionized Mg (Mg2+) were measured during day 3 of the IVF cycle, on the day of ovum pickup and 12 days following ET. Follicular fluid levels were measured on the day of ovum pickup. Serum levels of Mg2+ decreased and Ca2+ levels increased during the IVF cycle. Mg levels were significantly higher in follicular fluid than in serum. Ca2+ and Mg2+ may play a role in the preovulatory follicle, a possibility that warrants further study.

Structural and endocrine aspects of equine oocyte maturation in vivo

The objectives were to describe the ultrastructure of equine oocytes aspirated from small and preovulatory follicles, and to relate the ultrastructural features to follicle size and follicular fluid steroid concentrations. Mares were examined every second day by transrectal ultrasonography, and follicles measuring > 30 mm were aspirated (in vivo) using a 20-cm-long 12-gauge needle through the flank. Following slaughter, both large and small follicles were aspirated (in vitro) from six mares. The oocytes were isolated under a stereomicroscope and processed for transmission electron microscopy, and the follicular fluid was assayed for progesterone (P4) amd estradiol-17 beta (E2). A total of 29 oocytes (32% recovery rate) were aspirated in vivo, and 15 oocytes were recovered in vitro. According to the stage of nuclear maturation, the oocytes could be divided into the following six categories: 1) the central oocyte nucleus (CON) stage, 2) the peripheral spherical oocyte nucleus (PON-I) stage, 3) the peripheral flattened oocyte nucleus (PON-II) stage, 4) the oocyte nucleus breakdown (ONBD) stage, 5) the metaphase I (M-I) stage, and 6) the metaphase II (M-II) stage. The maturation of the preovulatory follicle was reflected by alterations in the follicular fluid concentrations of steroid hormones. E2 was high in all preovulatory follicles, whereas P4 concentration exhibited a 10-fold increase during follicle maturation, particularly associated with the progression from M-I- to M-II-stage oocytes. The nuclear oocyte maturation included flattening of the spherical oocyte nucleus, followed by increasing undulation of the nuclear envelope, formation of the metaphase plate of the first meiotic division, and, finally, the extrusion of the first polar body and the subsequent formation of the metaphase plate of the second meiotic division. The cytoplasmic oocyte maturation changes comprised breakdown of the intermediate junctions between the cumulus cell projections and the oolemma, enlargement of the perivitelline space, the formation and arrangement of a large number of cortical granules immediately beneath the oolemma, the rearrangement of mitochondria from a predominantly peripheral distribution to a more central or semilunar domain, and the rearrangement of membrane-bound vesicles and lipid droplets from an even distribution to an often semilunar domain, giving the ooplasm a polarized appearance. It is concluded that the final equine oocyte maturation includes a series of well-defined nuclear and cytoplasmic changes that are paralleled by an increase in P4 concentration in the follicular fluid, whereas E2 concentration remains constantly high.

Ovulation as a tissue remodelling process. Proteolysis and cumulus expansion

Ovulation, recurring every midcycle of the mammalian female and triggered by a surge of luteinizing hormone (LH) released from the pituitary, is an essential prerequisite for fertilization and subsequent embryonic development. Here we shall describe two of the biological components of the ovulatory response, cumulus expansion (frequently denoted as cumulus maturation) and the rupture of follicular wall, both crucial for the release of a fertilizable ovum. The role of a proteolytic cascade and its regulation by eicosanoids will be emphasized in relation to follicle rupture. The new data implicating cumulus maturation as an essential step for the release of the ovum and the apparent mediatory role of interleukin-1 in this process will be presented. LH/hCG stimulates, in the preovulatory follicles, a cascade of proteolytic enzymes, including plasminogen activator (PA), plasmin and matrix metalloproteinase 1 (MMP-1). These enzymes bring about the degradation of perifollicular matrix and, most notably, the decomposition of the meshwork of collagen fibers which provides the strength to follicular wall. Furthermore, pharmacological blockage of any of these enzymes resulted in inhibition of follicle rupture. LH/hCG stimulates, in addition, an increase in ovarian production of eicosanoids. These include prostaglandins, obtained from arachidonic acid via the cyclooxygenase pathway and leukotrienes, the products of lipoxygenase. Previous studies from our and other laboratories have demonstrated the ability of inhibitors of cyclooxygenase and of lipoxygenases to suppress ovulation in several mammalian species. MK-886, which inhibits the translocation of 5-lipoxygenase (5-LO) from the cytosol and its binding to the membranal 5-LO activating enzyme, suppressed dose-dependently follicular rupture from the treated ovary. Zymographic analysis of ovarian extracts from PMSG/hCG-stimulated rats revealed a band of collagenolytic activity at 52kD, corresponding to human MMP-1 and at 72kD, corresponding to human MMP-2. Both activities were markedly stimulated by administration of hCG and were significantly inhibited by indomethacin, NDGA or MK-886. Thus, eicosanoids seem to mediate LH stimulation of follicular collagenase. Interleukin-1 (IL-1) has been recently implicated in ovulation. The ability of an IL-1 receptor antagonist (ra) to block ovulation in vivo and in vitro has been demonstrated recently. Morphological examination of the ovulatory follicles failing to ovulate suggests that this effect is exerted by inhibiting cumulus oophorus expansion and detachment from mural granulosa cells. In vitro, IL-1ra attenuated the action of hCG and FSH on cumulus expansion and follicular hyaluronic acid synthesis. Thus, IL-1 seems to mediate and/or facilitate gonadotropin action on cumulus expansion, and hence on ovulation.

Interleukin-1 beta stimulates prostaglandin E2 and F2 alpha synthesis in human ovarian granulosa cells in culture

To evaluate the roles of interleukin-1 (IL-1) in regulation of ovarian prostaglandin (PG) synthesis, we examined the effects of IL-1 beta on PGE2, PGE2 alpha, 6-keto-PGF 1 alpha and thromboxane (TX) B2 synthesis in cultures of human ovarian granulosa cells. Granulosa cells were obtained from hyperstimulated follicles in patients undergoing oocyte retrieval for in vitro fertilization-embryo transfer (IVF-ET). IL-1 beta increased immunoreactive concentrations of PGE2 and PGF2 alpha in culture medium in time- and dose-dependent manners. Concentration of PGE2 was significantly higher after 24 h incubation with 5 or more units/ml of IL-1 beta, when compared to the control value obtained without IL-1 beta (P < 0.05). Concentration of PGF2 alpha was significantly higher after 8 h incubation with more than 2 units/ml of IL-1 beta (P < 0.05). The increase in PGE2 was observed even in the presence of human chorionic gonadotropin (hCG), and blocked by indomethacin, an inhibitor of cyclooxygenase. During a 10 day incubation period, stimulatory effects of IL-1 beta on PG synthesis were observed only on the first 2 days incubations. Concentrations of 6-keto-PGF 1 alpha and TXB2 were below our measurement limits. This study demonstrated that IL-1 beta stimulates PG synthesis in human ovarian granulosa cells in vitro. IL-1 seems to play an important role in regulating ovarian functions.

Eicosanoids and ovulation

PGs and probably other eicosanoids play a fundamental role in the process of ovulation, more specifically in the mechanism of follicle wall rupture. Although the nature of this role has yet to be established a number of plausible theories exist. It seems likely that altered PG metabolism is responsible for some cases of human female subfertility. The potential for fertility control by PG inhibition is an exciting possibility for the future.

New concepts in ovarian regulation: an immune insight

The purpose of the ovary is to produce eggs. In the human, oocyte production occurs cyclically at monthly intervals. The control of egg production is provided by both the endocrine and immune systems. Successful oocyte production is the result of sophisticated communication between the two systems. These interactions allow adaptive processes necessary for continuation of the species.

The effect of platelet activating factor on ovulation

The mechanism of ovulation has been compared to an inflammatory reaction. Platelet activating factor (PAF) is an important mediator of inflammation as it may induce the production of prostaglandins and lysosomal enzyme. We evaluated the potential role of PAF in PMSG-HCG induced ovulation using CV3988, a specific PAF receptor antagonist in a superovulated ICR mice (9-12 weeks old). CV3988 blocked the ovulation in a dose dependent manner, and the significant reduced ovulatory efficiency was observed at more than 500 micrograms dose (p less than 0.001). The ovulatory efficiency reduced by CV3988 was reversed by PAF in a dose dependent manner. In vitro fertilization (IVF) rate of follicular oocytes with treatment of CV3988 was not different from that of ovulated ova without treatment. These results suggest that PAF may be involved in the ovulation process but the presence of PAF may not be essential for the fertilization of the ova as IVF.

Prostaglandin F2 alpha in female water frog, Rana esculenta: plasma levels during the annual cycle and effects of exogenous PGF2 alpha on circulating sex hormones

Prostaglandin F2 alpha (PGF2 alpha) and sex hormones (progesterone, androgens, and estradiol-17 beta) have been determined in the plasma of female water frog, Rana esculenta, utilizing radioimmunoassay methods (RIA). Plasma PGF2 alpha level increases in autumn-winter when recovery processes interest both gonad and oviduct. The PGF2 alpha plasma highest value has been recorded in October (4.52 +/- 0.58 ng/ml) and the lowest in May (1.43 +/- 0.12). The PGF2 alpha annual pattern is positively correlated to that of estradiol (but not to those of progesterone and androgens). Exogenous PGF2 alpha, injected into intact females during the various phases of the annual cycle, induces an increase of ovarian weight in frogs treated in December and February and an increase of plasma estradiol in postreproductive animals (June). Although preliminary, such results propose a putative implication of PGF2 alpha in ovarian recovery processes and in the interruption of reproductive processes in late summer.

Home urinary luteinizing hormone immunoassays: clinical applications

Home ovulation prediction kits represent a valuable advance in monoclonal antibody technology and offer patients a quick, reliable, and relatively inexpensive means to predict the day of ovulation. These kits are used widely by patients trying to conceive and are commonly recommended by physicians involved in the care of infertile couples. They provide a more accurate and practical means to prospectively predict the time of ovulation than do BBT graphs or cervical mucus exams, and can be used as presumptive evidence of ovulation. Whereas ovulation prediction kits appear to be most useful for couples in timing sexual intercourse, other possible uses exist, including timing of AI, the PCT, and the endometrial biopsy for luteal phase evaluation. Despite multiple potential applications, clinical studies which support the use of urinary LH immunoassays in the evaluation and treatment of the infertile couple are quite limited. More well-designed studies to define the clinical value of ovulation prediction kits need to be undertaken.

Light and electron microscope immunocytochemical localization of 5- and 12-lipoxygenases and cyclooxygenase enzymes in human granulosa cells from preovulatory follicles

Cellular and subcellular distribution of 5- and 12-lipoxygenases and cyclooxygenase enzymes were investigated in human granulosa cells from preovulatory follicles using light and electron microscope immunocytochemistry. The results demonstrated that all three enzymes are present in granulosa cells but not in minor contaminating red blood cells. While the distribution of cyclooxygenase and 12-lipoxygenase was relatively uniform among the granulosa cells, 5-lipoxygenase was not uniformly distributed among these cells. All three enzymes are present in microvillus plasma membranes, rough endoplasmic reticulum, cytoplasm, nuclear membranes and chromatin. In summary, 5- and 12-lipoxygenases and cyclooxygenase enzymes, which catalyze the transformation of arachidonic acid into different eicosanoids, are present in several subcellular organelles including nuclei of granulosa cells from preovulatory follicles.

Prostaglandin F2 alpha, progesterone and estradiol concentrations in human follicular fluid and their relation to success of in vitro fertilization

Prostaglandin F2 alpha (PGF2 alpha), progesterone (P4) and estradiol-17 beta (E2) in follicular fluid were measured by radioimmunoassay in patients undergoing in vitro fertilization and embryo transfer. Follicular growth was induced using clomiphene citrate-hMG-hCG (15 patients) and FSH-hMG-hCG (4 patients). There was no significant difference in follicular fluid PGF2 alpha and P4 concentrations relative to oocyte maturity as assessed morphologically. The highest PGF2 alpha concentration was found in fluid from FSH-hMG-hCG cycles where fertilization occurred. The value is significantly higher (p less than 0.002) than in fluid from clomiphene-hMG-hCG cycles whether fertilization took place or not. There was no significant difference in P4 and E2 levels in relation to the type of ovarian induction or success in fertilization. Positive correlation between P4 and E2 in follicular fluid was found (r = 0.404). The positive correlation between total dose of hMG given to the patients and PGF2 alpha concentration in their preovulatory follicular fluid (r = 0.434) suggests that PGF2 alpha is secreted locally as the result of hMG and hCG stimulation. It is proposed that PGF2 alpha could be a biochemical marker for assessing the success of in vitro fertilization.

Stimulatory and inhibitory effects of prostaglandins on the gonadotropin-sensitive adenylate cyclase in the monkey corpus luteum

Detailed analysis of the action of prostaglandins (PGs) on the corpus luteum in primate species is very limited. In this study we examined the response of the adenylate cyclase system to PGs in homogenates prepared from the corpus luteum of rhesus monkeys at midluteal phase of the menstrual cycle. The conversion of [alpha 32p] ATP to [32p] cyclic AMP (cAMP) was assessed in the absence (control activity; 50 microM GTP) and presence of various concentrations of seven PGs and arachidonic acid, either alone or in combination with 250 nM hCG. Cyclic AMP production increased up to three-fold in the presence of PGD2, PGE2, PGI2 or PGF2 alpha; however PGA2, PGB2, 13, 14-dihydro-15-keto PGE2 and arachidonic acid alone did not alter cAMP levels. In dose-response studies, adenylate cyclase was 10 and 100-fold more sensitive to PGD2 (Vmax at 1 X 10(-5) M) than to PGE2 or to PGI2 and PGF2 alpha, respectively. Activity in the presence of hCG plus either PGD2, PGE2, PGI2 or PGF2 alpha did not differ from that for hCG (or the PG) alone. In contrast, addition of PGA2 or arachidonate inhibited (p less than 0.05) hCG-stimulated cAMP production by 50 and 100 percent. We conclude that the gonadotropin-sensitive adenylate cyclase of the macaque corpus luteum is also modulated by several PGs. These factors may either mimic (e.g., PGD2, PGE2, PGI2) or suppress (PGA2) gonadotropin-stimulated cAMP production and possibly cAMP-mediated events in luteal cells.