Possible involvement of lipoxygenase products of arachidonic acid pathway in ovulation

Hypoxia, NSAIDs, and autism: A biocultural analysis of stressors in gametogenesis

Cultural and generational trends have increasingly favored "anti-inflammatory" action, innovating a new class of analgesic, non-steroidal anti-inflammatory drugs (NSAIDs) in the 20th century. The modern human body has been molded over evolutionary time and while acknowledging inflammation can be pathologically entwined, it also serves an important role in healthy folliculogenesis and ovulation, shaping cues that drive needed vascular change. This review argues that because of anti-inflammatory action, the cultural invention of NSAIDs represents a particular stressor on female reproductive-age bodies, interacting with natural, underlying variation and placing limits on healthy growth and development in the follicles, creating potential autism risk through hypoxia and mutagenic or epigenetic effects. Since testes are analogs to ovaries, the biological grounding extends naturally to spermatogenesis. This review suggests the introduction of over-the-counter NSAIDs in the 1980s failed to recognize the unique functioning of reproductive-age bodies, challenging the cyclical inflammation needed for healthy gamete development. NSAIDs are framed as one (notable) stressor in an anti-inflammatory era focused on taming the risks of inflammation in modern human life.

Cellular and molecular mechanisms of the preovulatory follicle differenciation and ovulation: What do we know in the mare relative to other species

Terminal follicular differentiation and ovulation are essential steps of reproduction. They are induced by the increase in circulating LH, and lead to the expulsion from the ovary of oocytes ready to be fertilized. This review summarizes our current understanding of cellular and molecular pathways that control ovulation using a broad mammalian literature, with a specific focus to the mare, which is unique in some aspects of ovarian function in some cases. Essential steps and key factors are approached. The first part of this review concerns LH, receptors and signaling, addressing the description of the equine gonadotropin and cloning, signaling pathways that are activated following the binding of LH to its receptors, and implication of transcription factors which better known are CCAAT-enhancer-binding proteins (CEBP) and cAMP response element-binding protein (CREB). The second and major part is devoted to the cellular and molecular actors within follicular cells during preovulatory maturation. We relate to 1) molecules involved in vascular permeability and vasoconstriction, 2) involvement of neuropeptides, such as kisspeptin, neurotrophins and neuronal growth factor, neuropeptide Y (NPY), 3) the modification of steroidogenesis, steroids intrafollicular levels and enzymes activity, 4) the local inflammation, with the increase in prostaglandins synthesis, and implication of leukotrienes, cytokines and glucocorticoids, 5) extracellular matrix remodelling with involvement of proteases, antiproteases and inhibitors, as well as relaxin, and finaly 6) the implication of oxytocine, osteopontin, growth factors and reactive oxygen species. The third part describes our current knowledge on molecular aspect of in vivo cumulus-oocyte-complexe maturation, with a specific focus on signaling pathways, paracrine factors, and intracellular regulations that occur in cumulus cells during expansion, and in the oocyte during nuclear and cytoplasmic meiosis resumption. Our aim was to give an overall and comprehensive map of the regulatory mechanisms that intervene within the preovulatory follicle during differentiation and ovulation.

Expression and function of OXE receptor, an eicosanoid receptor, in steroidogenic cells

Hormonal regulation of steroidogenesis involves arachidonic acid (AA) metabolism through the 5-lipoxygenase pathway. One of the products, 5-hydroperoxy-eicosatetraenoic acid (5-HpETE), acts as a modulator of the activity of the steroidogenic acute regulatory (StAR) protein promoter. Besides, an oxoeicosanoid receptor of the leukotriene receptor family named OXE-R is a membrane protein with high affinity and response to 5-HpETE, among other AA derivatives. The aim of our work was to elucidate whether this receptor may be involved in steroidogenesis. RT-PCR and western blot analysis demonstrated the presence of the mRNA and protein of the receptor in human H295R adrenocortical cells. The treatment of H295R or MA-10 cells (murine Leydig cell line) with 8Br-cAMP together with docosahexaenoic acid (DHA, an antagonist of the receptor) partially reduced StAR induction and steroidogenesis. On the contrary, 5-oxo-ETE - the prototypical agonist, with higher affinity and potency on the receptor - increased cAMP-dependent steroid production, StAR mRNA and protein levels. These results lead us to conclude that AA might modulate StAR induction and steroidogenesis, at least in part, through 5-HpETE production and activation of a membrane receptor, such as the OXE-R.

Association of ALOX12 and ALOX15 gene polymorphisms with age at menarche and natural menopause in Chinese women

OBJECTIVE

Lipoxygenase (LOX) is one of the major metabolic enzymes for arachidonic acid, which has been reported to be associated with many postmenopausal and many hormone-related diseases. In rats, selective inhibition of the LOX pathway led to defective ovulation. However, little is known about the association of the LOX-related genes with menstruation in women. In this study, we investigated the possible association of two key gene (ALOX12 and ALOX15) polymorphisms with age of menarche and menopause in Chinese women.

METHODS

Six tagging single nucleotide polymorphisms (SNPs) of ALOX12 and five SNPs of ALOX15 were genotyped. The association of single SNPs and haplotypes in two candidate genes and age at menarche (AAM) variation was tested in 401 Chinese nuclear families using the quantitative transmissing disequilibrium test. Furthermore, the association between these SNPs and haplotypes and age at natural menopause (AANM) in 710 postmenopausal Chinese women was measured.

RESULTS

Using family- and population-based statistical procedures, significant association was found between SNPs rs312462 in ALOX12 and AAM in nuclear families (P = 0.043), and three SNPs (rs2292350, rs312470, and rs312462) in ALOX12 were significantly associated with AANM in postmenopausal women (P = 0.012, P = 0.045, and P = 0.033, respectively). Haplotype analyses corroborated our single SNP results (P = 0.030). However, we failed to find a significant association between ALOX15 gene polymorphisms and AAM as well as AANM (P > 0.05).

CONCLUSIONS

Our present results suggest that genetic variations in ALOX12 are associated with both the onset and cessation of menstruation in Chinese women living in Shanghai.

Inhibition of ovulation by a lipoxygenase inhibitor involves reduced cyclooxygenase-2 expression and prostaglandin E2 production in gonadotropin-primed immature rats

Potential roles of cyclooxygenase (COX) pathway of arachidonic acid (AA) metabolism are established in a murine model of induced ovulation. Pharmacological inhibition of an alternative lipoxygenase (LOX) pathway has been shown to cause defective ovulation, but the mechanism is still undefined. This study investigated the effects of two LOX inhibitors and their time dependency on ovulation and COX activity in gonadotropins (eCG and human chorionic gonadotropin (hCG))-primed immature rats. Intra-ovarian bursal treatment with a general LOX inhibitor nordihydroguaiaretic acid (NDGA) at 0 h post-hCG (hCG0h) dose dependently inhibited ovulation rate. The drug was still but less effective when treated at hCG6h. A more specific inhibitor, 3,4-dihydroxyphenyl ethanol (DPE) was also inhibitory when treated at hCG0h but not at hCG6h. Interestingly, treatment with DPE at hCG0h resulted in attenuated expression of immunoreactive PTGS2 in granulosa layers and concomitant decrease in ovarian prostaglandin E(2) (PGE(2)) content at hCG8h. NDGA treatment reduced immunoreactive PTGS2. Ovulatory impairment by both inhibitors was prevented by systemic administration of PGE(2) at hCG6h. Immunohistochemistry revealed the expression of ALOX5 and ALOX12 in both thecal and granulosa layers of preovulatory follicles and, notably, the augmented immunoreactivities during 8 h after hCG treatment. Our results indicate the probable presence of multiple LOX isoforms and that specific inhibition of LOX at an early stage of hCG-signaling led to reduced PTGS2 activity and thus defective ovulation. They reveal a probable relationship between two pathways of AA metabolism and account at least partly for the mechanism by which the LOX inhibitor causes impaired ovulation.

Effects of selective inhibition of cyclooxygenase and lipooxygenase pathways in follicle rupture and ovulation in the rat

Treatment with non-steroidal anti-inflammatory drugs, either non-selective or selective cyclooxygenase-2 (COX-2) inhibitors, consistently impairs ovulation, indicating the essential role of COX-2/prostaglandins in the ovulatory process. Indomethacin, a potent inhibitor of both COX-1 and COX-2, induced several ovulatory alterations, consisting of a decrease in the number of oocytes effectively ovulated, trapping of oocytes inside the luteinized follicle, as well as abnormal follicle rupture at the basolateral sides, with release of the oocyte and follicular fluid to the interstitium. Yet, the precise role of prostaglandins in ovulation and whether some of the ovulatory defects induced by indomethacin are due to interference with additional components of the ovulatory cascade, beyond prostaglandin synthesis, are not completely understood. We have used gonadotrophin-primed immature rats to analyse whether, compared to indomethacin, selective inhibition of COX-2, with or without concomitant inhibition of COX-1, or selective inhibition of the lipooxygenase (LOX) pathway, induce similar ovulatory alterations. Immature rats (27 days of age) were injected PMSG (10 IU), and 48 h later hCG (10 IU) subcutaneously, and different anti-inflammatory drugs. Animals were killed at 21 h after hCG injection. Rats treated with the selective COX-2 inhibitor NS398 (10 mg/kg body weight, (bw)) showed alterations in follicle rupture as those treated with indomethacin (0.5 mg/rat), albeit affecting a lower number of follicles, irrespective of the concomitant inhibition of COX-1 with the selective inhibitor SC560 (10 mg/kg bw). Rats treated with the LOX inhibitor NDGA (300 mg/kg bw) did not show ovulatory alterations. These data indicate that the characteristic alterations of follicle rupture induced by indomethacin, are also induced by selective COX-2 inhibitors, strengthening the contention that prostaglandins play a crucial role in the spatial targeting of follicle rupture at the apex.

A Novel Pathway Involving Progesterone Receptor, 12/15-Lipoxygenase-derived Eicosanoids, and Peroxisome Proliferator-activated Receptor γ Regulates Implantation in Mice

The 12/15-lipoxygenases (12/15-LOX) catalyze the stereo-specific oxygenation of arachidonic and linoleic acids into a complex series of signaling molecules, including the hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecadienoic acids (HODEs). Our previous studies, using high density oligonucleotide microarrays, suggested a novel link between progesterone receptor (PR) signaling and 12/15-LOX-mediated fatty acid metabolism in preimplantation mouse uterus. In this paper, using PR knockout mice, we established that the transcripts encoding leukocyte-12/15-LOX (L-12/15-LOX) and epidermal-12/15-LOX (E-12/15-LOX) are indeed downstream targets of regulation by PR in the uterine surface epithelium. Maximal induction of both L- and E-12/15-LOX on the day of implantation resulted in a marked increase in the uterine levels of the eicosanoids, 12-HETE, 15-HETE, and 13-HODE. Mice with null mutation in L-12/15-LOX had significantly reduced uterine levels of arachidonic acid metabolites and exhibited a partial impairment in implantation. Complete blockade of uterine 12/15-LOX activity by a specific inhibitor led to greater than 80% reduction in a number of implantation sites relative to untreated controls. Cell-based assays indicated that 12-HETE, 15-HETE, and 13-HODE function as activating ligands of peroxisome proliferator-activated receptor gamma (PPARgamma), suggesting that this nuclear receptor could be a downstream target of 12/15-LOX-derived metabolites in the preimplantation uterus. Consistent with this hypothesis, administration of rosiglitazone, a potent PPARgamma-selective agonist, efficiently reversed inhibition of implantation by the 12/15-LOX-specific inhibitor. Rosiglitazone also induced a number of potential target genes of 12/15-LOX-derived metabolites in the pregnant uterus, indicating their regulation by PPARgamma. Collectively, our results uncovered a novel signaling pathway in which progesterone-induced synthesis of the 12/15-LOX-derived lipid mediators activates PPARgamma and its downstream gene networks, which in turn function as critical regulators of implantation in the mouse.

Nonsteroidal anti-inflammatory drugs and reversible female infertility: is there a link?

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently prescribed to women of child-bearing age. Three case series highlight the possibility of a link between NSAIDs and reversible infertility. The pharmacological target of NSAIDs is cyclo-oxygenase (COX), which catalyses the first rate-limiting step in the production of prostaglandins. COX-2, one of two isoenzymes, is active in the ovaries during follicular development. Its inhibition is thought to cause luteinised unruptured follicle (LUF) syndrome, an anovulatory condition characterised by clinical signs of ovulation but in the absence of follicular rupture and ovum release. The evidence linking regular NSAID use to reversible LUF syndrome comes from animal studies and three clinical studies. COX-2-deficient mice have severely compromised ovulation in the presence of apparently normal follicular development. Experimental administration of prostaglandins induced ovulation in rabbits and this was blocked by the administration of indomethacin. The three clinical studies demonstrated the induction of delayed follicular rupture or LUF in previously ovulating women by the administration of NSAIDs. A link can therefore be identified between NSAID use and reversible female infertility and NSAID withdrawal should be considered prior to or concurrent with fertility investigations.

Localization of plasminogen in the extracellular matrix of hamster eggs: exogenous activation by streptokinase

The plasminogen activator (PA)/plasminogen/plasmin proteolytic system has begun to be taken into account in the fertilization process. In this study, we demonstrated the presence of plasminogen in the extracellular matrix (ECM) of hamster oocytes by indirect immunofluorescence and immunoperoxidase assays using human anti-plasminogen. Plasminogen appeared first on the zona pellucida (ZP) of ovarian oocytes and later on the plasma membrane (PM) of oviducal eggs. This would suggest that oviducal oocytes modulate the expression of plasminogen binding sites on the PM. Human plasminogen as well as that of other species, known to be activated by streptokinase (SK), is rapidly converted to a plasmin-SK complex. We demonstrated the rapid formation of a SK-plasminogen complex that yields plasmin in the blood plasma of hamsters. Both the in vivo and in vitro SK treatment of eggs from superovulated female hamsters caused a decreased in the ZP dissolution time (ZPdt), probably either due to the proteolytic effect of plasmin or due to the SK-Plasminogen. Extracellular proteolysis assays carried out on agar-casein plates confirmed the proteolytic activity of SK-incubated eggs; the controls, on the contrary, failed to display a halo. These studies show that (1) superovulated hamster eggs contain plasminogen in their ECM, (2) oviducal eggs exhibit plasminogen on their PMs, indicating the presence of their corresponding binding sites, (3) in hamsters, SK, a non-enzymatic exogenous protein would be capable of activating ECM plasminogen to plasmin, and (4) the complex SK-plasminogen and/or the plasmin are capable of changing the ZPdt with alpha-chymotrypsin.

Role of meiosis-activating sterols in rat oocyte maturation: effects of specific inhibitors and changes in the expression of lanosterol 14alpha-demethylase during the preovulatory period

In vitro studies on mouse oocytes have shown that two closely related sterols, subsequently named meiosis-activating sterols (MAS), can overcome the inhibitory effect of hypoxanthine on the resumption of meiosis. These sterols are synthesized by cytochrome P(450) lanosterol 14alpha-demethylase (LDM), a key enzyme in cholesterol biosynthesis. We have used specific inhibitors of LDM, azalanstat (RS-21607) and RS-21745, to test whether MAS is an obligatory mediator in the resumption of meiosis in the rat. Addition of azalanstat and RS-21745 (1-200 microM) to culture medium of rat isolated cumulus-enclosed oocyte and preovulatory follicle-enclosed oocyte stimulated by LH/hCG did not allow separation between their inhibition of the resumption of meiosis and the degeneration of oocytes. In both models, doses of the drug that inhibited oocyte maturation also increased oocyte degeneration. The inhibitors only partially suppressed follicular progesterone production. We have examined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunocytochemistry the ovarian expression of LDM mRNA and protein during the preovulatory period. We did not find evidence for the stimulation of this enzyme by LH/hCG. The strongest staining by LDM antiserum was obtained in primordial and primary oocytes, and the staining was reduced with oocyte growth. In addition, strong LDM staining could be observed in some of the granulosa cells, especially of the corona radiata localized in close proximity to the oocyte. In conclusion, our results with specific inhibitors and molecular approaches do not reveal evidence to support the hypothesis that MAS is an obligatory step in the stimulation of the resumption of meiosis. Specific inhibitors of MAS synthesis did not prevent spontaneous or LH-stimulated meiosis at doses that have previously been shown to effectively suppress LDM activity. Much higher concentrations of the inhibitors, which affected meiosis, were detrimental to oocytes, leading to their degeneration. The timing of LDM expression in the ovary was incompatible with a role for MAS in meiosis. Finally, the preferential localization of LDM protein to the oocytes suggests MAS production in oocytes rather than its transport from the somatic compartment as implied by the proposed role of MAS as a cumulus-oocyte signal molecule.

Eicosatetraynoic and eicosatriynoic acids, lipoxygenase inhibitors, block meiosis via antioxidant action

We previously showed that nordihydroguaiaretic acid (NDGA) and other antioxidants inhibit the resumption of meiosis in oocyte-cumulus complexes (OCC) and denuded oocytes (DO). Because NDGA is well known to be an inhibitor of lipoxygenases (LOX), we assessed whether other LOX inhibitors influence spontaneous germinal vesicle breakdown (GVBD) in OCC and DO. Spontaneous GVBD in rat OCC obtained from preovulatory follicles was significantly and reversibly inhibited by the minimum effective doses of 80 and 100 microM 5,8,11, 14-eicosatetraynoic acid (ETYA) and 5,8,11-eicosatriynoic acid (ETI), respectively. In DO, GVBD was significantly inhibited by 100 microM ETYA or ETI. The minimum effective concentrations of ETYA and ETI for inhibition of GVBD in either OCC or DO are approximately 30- to 50-fold higher than the concentrations necessary to inhibit LOX activity by 50% in intact cells. Because we previously showed that NDGA and other antioxidants inhibit the spontaneous resumption of meiosis, we assessed whether ETYA and ETI may act similarly as scavengers of reactive oxygen species (ROS). Luminol-amplified chemiluminescence showed that 50 microM of either ETYA or ETI markedly and significantly reduced ROS generated with 10 mM 2, 2'-azobis(2-amidinopropane)dihydrochloride (AAPH). Moreover, incubation of DO with 30 mM AAPH reversed the inhibition of GVBD produced by 100 microM ETYA or ETI. These findings support the conclusion that ETYA and ETI inhibit oocyte maturation by acting as antioxidants rather than by inhibiting LOX.

Signal transduction involving cyclic AMP-dependent and cyclic AMP-independent mechanisms in the control of steroidogenesis

The control of steroidogenesis via signal transduction mechanisms involving cAMP-dependent and cAMP-independent mechanisms is reviewed. Several structurally unrelated factors that are potent stimulators of steroidogenesis whose actions do not require cAMP and/or synthesis of proteins have been identified. These include various interleukins, a lipophilic factor from macrophages, a steroidogenic inducing protein from follicular fluid and an imidazole compound, calmidazolium. All of these factors are capable of inducing maximum steroidogenesis. Calcium is required for steroidogenesis in all steroidogenic cells. With the exception of the effects of angiotensin II, there is little evidence for a role of IP3 in the stimulation of the release of calcium from intracellular stores in steroidogenic cells under physiological conditions. There may however, be a cAMP-mediated activation of a plasma membrane calcium channel. Chloride channels that can be regulated by cAMP-dependent and -independent mechanisms, are present in steroidogenic cells. Chloride ions exert a negative effect on steroidogenesis because exclusion of chloride from the extracellular medium markedly enhances cAMP-stimulated steroidogenesis. Arachidonic acid and its lipoxygenase products are involved in the control of steroidogenesis via cAMP mediated processes. An arachidonic acid related thioesterase has been isolated that is activated by ACTH and which may be involved in the release of arachidonic acid. It is concluded that while cAMP is a second messenger for LH/ACTH in the control of steroidogenesis, other signalling systems exist which are potentially equally effective in controlling steroidogenesis. In addition, the action of cAMP requires other signalling pathways involving calcium and chloride ions, as well as arachidonic acid and its lipoxygenase products.

A role for lipoxygenase metabolites of arachidonic acid in porcine ovulation

Prostaglandins, products of arachidonic acid via the cyclooxygenase pathway, are essential to the porcine ovulatory process in that inhibition of their synthesis results in ovulation failure. Studies in the rat have shown that ovulation is also preceded by a rise in three ovarian hydroxyeicosatetraenoic acids, products of the lipoxygenase pathway, and inhibition of this pathway also inhibits ovulation. Experiments were designed, using a pregnant mare serum gonadotropin/human chorionic gonadotropin (hCG)-treated prepuberal gilt model, to measure pre-ovulatory changes in follicular fluid concentrations of 15-hydroxyeicosatetraenoic acid (15-HETE), and to compare the effects of indomethacin and nordihydroguaiaretic acid (NDGA) on ovulation in the pig and on 15-HETE and prostaglandin F2 alpha synthesis both in vivo and in vitro. Follicular fluid concentrations of 15-HETE were elevated significantly just prior to the expected time of ovulation (40 h after hCG). When indomethacin (10 mg) was injected into the ovarian stalk at 24 h after hCG, follicular fluid concentrations of both 15-HETE and prostaglandin F2 alpha were lower (P < 0.01) than controls at 40 h and ovulation rate was suppressed (P < 0.01). When NDGA (5 mg) was administered in the same manner, ovulation rate was suppressed (P < 0.01), but the levels of 15-HETE and prostaglandin F2 alpha were not altered. Synthesis of 15-HETE by cultured granulosa and theca interna cells was reduced by the presence of NDGA (1 mg/ml), whereas indomethacin (100 ng/ml) lowered 15-HETE production in theca interna cells only. These results clearly demonstrate that indomethacin can block the lipoxygenase as well as the cyclooxygenase pathways, depending on the dose used, and suggest that lipoxygenase metabolites of arachidonic acid are involved in the ovulatory process in the pig.

Different time-course production of peptidic and nonpeptidic leukotrienes and prostaglandins E2 and F2 alpha in the ovary during ovulation in gonadotropin-primed immature rats

Temporal changes in ovarian leukotrienes (LTs) and prostaglandins (PGs) were examined during ovulation to assess roles they may play in this process. Ovulation was induced in immature rats by injection with human chorionic gonadotropin (hCG; 10 IU, s.c.) 2 days after they had been primed with pregnant mare serum gonadotropin (10 IU, s.c.). The ovaries were extirpated at various intervals after hCG administration and assayed for LTB4, and LTC4/D4/E4, as well as PGE2, and PGF2 alpha. Ovarian concentration of LTB4 increased (P < 0.01) rapidly, reaching a peak at 1 hour after hCG administration, then declined (P < 0.05) by 4 hours and remained low thereafter. In contrast, LTC4/D4/E4 peaked (P < 0.01) between 1 and 2 hours, declined (P < 0.05), and then increased (P < 0.01) to achieve a second, larger peak at 10 hours. Prostaglandin E2 increased (P < 0.01) at 6 hours after hCG and did not decrease from the peak value until (P < 0.01) 14 hours after hCG. Concentrations of PGF2 alpha increased (P < 0.01) at 4 hours after hCG, but decreased (P < 0.01) from the peak by 10 hours. Although LTB4, LTC4/D4/E4, PGE2, and PGF2 alpha all increased during ovulation, the time-course differed. This suggests that each eicosanoid may play a distinct role in the process of follicular rupture.

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.

The inhibitory effects of indomethacin, nordihydroguaiaretic acid, and pyrrolidinedithiocarbamate on ovulation and prostaglandin synthesis in yellow perch (Perca flavescens) follicle incubates

This study specifically determined the correlation between ovulation and ovarian prostaglandin F (PGF) and prostaglandin E (PGE) levels in yellow perch follicles treated with several eicosanoid synthesis inhibitors. In incubates treated with indomethacin (IM; .00001 to 10.0 micrograms/ml) there was a significant dose-dependent correlation between ovulation and PGF/PGE levels, and between the two prostaglandins (PGs), further implicating PGs in the control of yellow perch ovulation. In incubates treated with nordihydroguaiaretic acid (NDGA), a traditional lipoxygenase inhibitor, there was a significant correlation between ovulation and PGF levels, yet there was no correlation between PGE levels and ovulation. A free-radical scavenger, pyrrolidinedithiocarbamate (PDTC) inhibited ovulation in a dose-dependent manner yet there was no correlation between either PGF or PGE levels and this inhibition, indicating that PDTC may block ovulation at other steps that involve free-radicals.

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.

The angiotensin II antagonist saralasin inhibits ovulation in the perfused rat ovary

OBJECTIVE

Our null hypothesis was that the angiotensin II antagonist saralasin does not reduce the number of ovulations in the rat ovarian perfusion model.

STUDY DESIGN

Ovaries from pregnant mare's serum gonadotropin-stimulated immature rats were perfused with nutrient media to which luteinizing hormone and 3-isobutyl-1-methylxanthine had been added to induce ovulation. Test perfusions were treated with saralasin 1 mumol/L (n = 0.5) and compared with controls (n = 5) with the Student t test. Perfusions with both saralasin and angiotensin II and dose-response evaluations were performed.

RESULTS

Saralasin-treated ovulations were 6.6 +/- 1.3 (mean + SEM) compared with 18.6 +/- 3.9, p < 0.02. The effects of saralasin could be reversed with the addition of an equimolar amount of angiotensin II. Dose-response evaluations showed a progressive inhibition of ovulation at 10(-8) to 10(-6) mol/L.

CONCLUSION

The angiotensin II antagonist saralasin inhibits ovulation in a dose-dependent fashion; this effect is canceled by the addition of equimolar concentrations of angiotensin II.

Prostaglandins in the ovary and fallopian tube

More than 20 years following the recognition of a possible role for eicosanoids in ovarian function a physiological role for prostaglandins and/or leukotrienes in human ovulation, corpus luteum function and tubal motility remains to be demonstrated. With respect to ovarian function, the well-characterized preovulatory rise in eicosanoid production in animal species and humans, in conjunction with the large body of experimental evidence employing inhibitors of prostaglandin synthesis and replacement of individual prostaglandins, has provided strong evidence for a role in follicular rupture independent of other LH-mediated ovulatory events. The possible mechanism of prostaglandin-induced follicle rupture may involve stimulation of proteolytic activity via substances such as plasmin and PA; however, this is controversial. A role for prostaglandins in ovarian luteal function is well established in laboratory animals and large ruminant species, where PGF2 alpha derived from the uterus has been demonstrated to be the luteolytic factor. In humans, luteal function may be influenced by local intraovarian eicosanoid production, which has been suggested to involve the paracrine interaction of local ovarian hormones such as oxytocin, noradrenaline, insulin and IGFs, to name but a few. Several lines of evidence have also implicated prostaglandins as an aetiological factor in ovarian pathological states such as seen in the OHSS. However, the bulk of clinical experimental evidence to date has failed to support this contention. Prostaglandin production has likewise been well characterized in the fallopian tube in both humans and animal species. Whereas a role for prostaglandins in tubal transport has been demonstrated with animal species such as the rabbit, several studies have failed to define a similar function in humans. More recently, direct injections of prostaglandin analogues into the fallopian tube and the corpus luteum have been shown to be efficacious as a treatment for ectopic pregnancy. Whether the primary mechanism of action involves effects on tubal musculature or corpus luteum function, or is simply a local vascular effect, remains to be demonstrated. Therefore, although the physiological role for eicosanoids in ovarian and tubal function remains unclear, particularly in the human, an increasing body of recent evidence has suggested an important paracrine function for this class of cellular mediators whose interaction with other more recently characterized local ovarian factors has only begun to be recognized.

Comparison of inhibitory actions of indomethacin and epostane on ovulation in rats

Indomethacin, an inhibitor of cyclooxygenase that generates prostaglandins (PGs) from arachidonic acid, and 2 alpha,4 alpha,7-4,5-epoxy-17-hydroxy-4,17-dimethyl-3-oxoandrostane- 2-carbonitrile (epostane), an inhibitor of 3 beta-hydroxysteroid dehydrogenase that generates progesterone from pregnenolone, are both potent inhibitors of ovulation. This report compares the dose-dependent effects of these two inhibitors on ovarian levels of 5-, 12-, and 15-hydroxyeicosatetraenoic acid methyl ester (HETEs), prostaglandin E2 (PGE), prostaglandin F2 alpha (PGF), progesterone, 17 alpha-hydroxyprogesterone, 17 beta-estradiol, 4-androstene-3,17-dione, and testosterone during ovulation in 25-day-old immature Wistar rats. The ovulatory process was initiated by 10 IU of human chorionic gonadotropin (hCG). Indomethacin was given at 3 h after hCG in doses ranging from 0.0316 to 10.0 mg/rat. A dose of 0.1 mg/rat was the lowest dose to significantly reduce the ovulation rate from the control level of 70.5 +/- 5.8 ova/rat. This dose also reduced 15-HETE, but not 5-HETE, 12-HETE, or the steroids. PGE and PGF were strongly inhibited by an even lower dose of indomethacin (0.0316 mg/rat), but this dose did not affect the ovulation rate. Epostane was given at 3 h after hCG in doses ranging from 0.1 to 5.0 mg/rat. A dose of 1.0 mg/rat was the lowest dose to significantly inhibit ovulation. This dose also reduced the ovarian levels of 15-HETE and progesterone but not 5-HETE, 12-HETE, PGE, PGF, or the other steroids. The results indicate that the ovulation rate is most closely correlated to ovarian 15-HETE levels.

Ovarian hydroxyeicosatetraenoic acids compared with prostanoids and steroids during ovulation in rats

Hydroxyeicosatetraenoic acid methyl esters (HETEs) are lipoxygenase products of arachidonic acid that are generated along with prostaglandins (PGs) during acute inflammatory reactions. Whereas it is well known that ovarian PG levels increase during the ovulatory process, little is known about ovarian HETEs. This report compares the ovarian changes in 5-, 12-, and 15-HETE with ovarian PGE and PGF, along with progesterone, 17 alpha-hydroxyprogesterone, 4-androstene-3,17-dione, testosterone, and 17 beta-estradiol. Ovulation was induced in immature Wistar rats by sequential treatment with pregnant mare's serum gonadotropin and human chorionic gonadotropin (hCG). Follicles began rupturing 10 h after hCG treatment. The greatest correlation was among 12-HETE, 15-HETE, and progesterone, which increased to peak levels at 10 h after hCG. In contrast, the ovarian levels of 5-HETE, 17 alpha-hydroxyprogesterone, testosterone, and 17 beta-estradiol all declined sharply beginning 4 h after hCG. 2 alpha,4 alpha,7-4,5-Epoxy-17-hydroxy-4,17-dimethyl-3-oxo-androstane-2- carbonitrile (epostane), a potent inhibitor of steroid synthesis and ovulation, sharply reduced the synthesis of all five steroids within 30 min after its injection at 3 h after hCG. Among the five eicosanoids, epostane mainly inhibited 15-HETE. The results suggest that 15-HETE, along with progesterone, may have an important role in ovulation.

Effect of nordihydroguaiaretic acid on luteal phase length and oxytocin-induced release of prostaglandin F2 alpha in heifers

Two experiments were conducted to determine if intrauterine infusion of nordihydroguaiaretic acid, a lipoxygenase pathway inhibitor, would delay luteolysis (Experiment 1) and inhibit oxytocin-induced release of prostaglandin F2 alpha (as measured by the stable prostaglandin F2 alpha metabolite, 15-keto-13,14-dihydroprostaglandin F2 alpha) in plasma on d 16 (d 0 = estrus) of the estrous cycle (Experiment 2). Nordihydroguaiaretic acid (20 mg) or saline was infused twice daily into the uterus on d 14 to 23 (Experiment 1) or d 14 to 20 (Experiment 2) postestrus, respectively. In Experiment 1 and 2, mean concentration of progesterone was higher and luteolysis was delayed in nordihydroguaiaretic acid-infused heifers compared with saline-infused heifers. In Experiment 2, saline or oxytocin (100 IU, i.v.) was injected into each heifer on d 16 postestrus to stimulate the release of prostaglandin F2 alpha from the uterus. Mean concentration of 15-keto-13,14-dihydroprostaglandin F2 alpha increased within 1.5 h postinjection in heifers infused with saline, whereas concentration of 15-keto-13,14-dihydroprostaglandin F2 alpha in nordihydroguaiaretic acid-infused heifers did not increase within the same time period. Thus, nordihydroguaiaretic acid may inhibit both the lipoxygenase and cyclooxygenase pathways of arachidonic acid metabolism and therefore delay luteolysis.

Inhibitors of lipoxygenase increase the ovulation rate in the in-vitro perfused luteinizing hormone-stimulated rabbit ovary

In order to determine whether leukotrienes, products of the lipoxygenase pathway, are involved in ovulation, pairs of rabbit ovaries were treated with the lipoxygenase inhibitors nordihydroguaiaretic acid (NDGA) and caffeic acid (CA) while being perfused in vitro. The control ovaries from each rabbit received luteinizing hormone (LH) (1.5-2.25 micrograms ml-1) while the contralateral ovaries were treated with LH + NDGA (100 microM) or LH + CA (100 microM). The numbers of ovulations from both the LH + NDGA- and LH + CA-treated ovaries were significantly higher (P less than 0.05) than from their respective LH-stimulated controls. Treatment with NDGA alone in the perfusate did not cause any ovulation, while CA alone caused one ovulation from one of six ovaries perfused. Ovarian tissue levels of prostaglandins after 7 h of perfusion with LH + NDGA or with LH alone showed that, in five of the six ovaries perfused in this group, the tissue levels of PGE2, 6-keto-PGF1 alpha and PGF2 alpha were higher in the presence of NDGA. The mean differences were significant (P less than 0.05) for prostacyclin but not significant (P greater than 0.05) for PGE2 and PGF2 alpha. Our interpretation of the findings is that, when used for blocking the lipoxygenase pathway, NDGA and CA increase the substrate availability for the cyclo-oxygenase pathway of arachidonic acid metabolism, resulting in a net increase in prostaglandins. The increased ovarian levels of prostaglandins, especially prostacyclin, may cause the observed increase in ovulation rate. Consequently, although the leukotrienes may be involved in the mechanism of ovulation in the rabbit, their effects appear to be less pronounced than those of prostaglandins.

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.

Mechanism of mammalian ovulation

The sequence of events within the ovary during the process of ovulation discussed in this review is schematically represented in Fig. 1. It is obvious that LH, perhaps with some contribution from FSH, is the normal physiological trigger for the ovulatory sequence of events, and it appears from the available information that the effects of LH are mainly mediated via adenylate cyclase and increased cAMP levels. The cAMP in turn, via cAMP-dependent protein kinase, influences at least three distinct steps in the ovulatory process which seem to be of crucial importance, namely 1) the stimulation of steroidogenesis; 2) the stimulation of cyclooxygenase/lipooxygenase leading to increased prostaglandin/leukotriene synthesis; and 3) the stimulation of plasminogen activator which catalyzes the conversion of plasminogen to plasmin. A fourth crucial step in the ovulatory mechanism is the LH-induced increase in latent collagenase, but it remains to be determined if this step is mediated via cAMP. Concomitant with the increase in latent collagenase, there also appears to be an LH-dependent increase in collagenase inhibitors. The latent collagenase is then activated, and it appears that leukotrienes and prostaglandins, as well as plasmin, may be involved in this process. The active collagenase causes a digestion of the collagen in the follicle wall, and plasmin, as well as possibly other proteolytic enzymes such as proteoglycanases, may cause a further dissociation of the follicular wall. These processes of digestion of collagen and dissociation of the collagen fibers result in an opening in the follicular wall with the formation of the stigma and rupture. While the weakening of the follicular wall takes place throughout the entire wall, rupture remains for the most part a localized process at the apex of the follicle. This localization of the rupture may be explained on the basis of mechanical factors operating when the follicle wall thins and weakens. While it is clear that prostaglandins and leukotrienes can influence smooth muscle by causing contractions and that these compounds can cause vascular changes such as increased permeability, vasodilation, and vasoconstriction, it is not clear what the exact role of these latter processes are in ovulation. It appears that progesterone and not estrogen play an important role in the mechanism of LH-induced follicular rupture, but the locus of action of progesterone and its mechanism of action remains to be determined.(ABSTRACT TRUNCATED AT 400 WORDS)

Ovarian follicular fluid eicosanoid concentrations during the pre-ovulatory period in humans

Prostaglandins are involved in ovulation and in every mammal studied so far, ovulation has been inhibited by prostaglandin inhibition. Information regarding the role of leukotrienes and thromboxanes in ovulation is more limited. In order to study the production of eicosanoids in human pre-ovulatory follicular fluid, follicular aspiration was timed by means of serial ultrasound scans and human chorionic gonadotrophin (hCG) to be immediately pre-ovulatory. 11 women were studied and the eicosanoids measured by radioimmunoassay (RIA). The follicular fluid was found to contain leukotrienes (LT) B4, LTC4 (D4, E4), prostaglandin (PG) E2, PGF2 alpha 6 keto PGF1 alpha k and thromboxane (TX) B2. This is the first published report of leukotrienes in human follicular fluid in spontaneous cycles, and is one of the few reports showing prostaglandins and thromboxanes. The significance of demonstrating leukotrienes in human follicular fluid is discussed as is the correlation between individual eicosanoids in the human ovary.

Desensitization to follicle-stimulating hormone in cumulus cells is coincident with hormone induction of oocyte maturation in the rat follicle

The objective of the present studies was to assess whether hormone induction of oocyte maturation in isolated intact follicles may be linked to desensitization of follicle-stimulating hormone (FSH) in the oocyte-cumulus complex (OCC). Incubation of follicles with chorionic gonadotropin (hCG), FSH or epidermal growth factor (EGF) produced a marked inhibition of FSH-dependent cyclic AMP accumulation in OCC with a time-course coincident with the onset of germinal vesicle breakdown (GVBD). These effects were evident within 3 h for both hCG and FSH, but with EGF a reduced response to FSH was seen within 1 h of treatment followed by an increase in GVBD. In contrast, no inhibition of cyclic AMP accumulation was seen in response to cholera toxin, forskolin or LH in OCC derived from follicles incubated with hCG for 3 h. The time-course for induction of oocyte maturation by incubation of the intact follicle with hCG was also coincident with production of prostaglandin (PG) F2 alpha, an indirect marker of cyclooxygenase induction. No effect on metabolic coupling between the oocyte and cumulus cells was seen until 9 h after hCG treatment. Retinoic acid caused a marked decrease in metabolic coupling between the oocyte and cumulus cells but inhibited oocyte maturation both in denuded oocytes and OCC. Since FSH desensitization in OCC, the resumption of meiosis, and production of arachidonic acid-derived products were coincident, it is suggested that abrogation of FSH action in cumulus cells by the ovulatory surge of gonadotropins may initiate oocyte maturation.

Increase in ovarian leukotrienes during hormonally induced ovulation in the rat

The ovulatory process was initiated in 25-day-old Wistar rats by injecting human chorionic gonadotropin (hCG; 10 IU sc) 2 days after the animals had been primed with pregnant mares serum gonadotropin (PMSG; 10 IU sc). By 4 h into the ovulatory process, leukotriene (LT) B4 increased 2-fold (P less than 0.001) and LTs C4/D4/E4 increased 1.3-fold (P less than 0.002). By the time of ovulation (10-12 h after the administration of hCG) both eicosanoids declined to their pre-hCG levels. When animals were treated with the cyclooxygenase inhibitor indomethacin at the specific dose of 0.316 mg/rat sc at 1 h before hCG, the ovarian levels of LT B4 and LTs C4/D4/E4 increased to 210% (P less than 0.01) and 113% (P less than 0.05), respectively, above the control levels at 4 h after hCG. Concomitantly, this dosage of indomethacin reduced ovarian prostaglandins (PGs) E and F by 99% (P less than 0.001) and 98% (P less than 0.001), respectively, and it reduced the ovulation rate by 76% (P less than 0.001). Thus it appears this dose of indomethacin blocked the conversion of ovarian arachidonic acid into PGs and shunted this substrate into the lipoxygenase pathways that lead to LT formation. In conclusion, the moderate increase in ovarian LTs is characteristic of inflammatory reactions, and, therefore, these data support the hypothesis that the biochemical events of ovulation resemble an inflammatory process.

Significance of follicular cyclooxygenase and lipoxygenase pathways of metabolism of arachidonate in sheep

Concurrent changes in concentrations of a product of the cyclooxygenase (prostaglandin [PG] F2 alpha) and lipoxygenase (leukotriene [LT] B4) routes of metabolism of arachidonic acid were measured by radioimmunoassay within the wall of periovulatory ovine follicles. Increased concentrations of PGF2 alpha were detected within follicles before, during and following the time of ovulation. A significant rise in LTB4 was not observed until after follicular rupture had occurred. Inhibition of synthesis of PGF2 alpha by indomethacin was associated with a complete blockade of ovulation. Nordihydroguaiaretic acid, an inhibitor of 5-lipoxygenase, had no effect on ovulation. Periovulatory administration of either drug did not alter sera profiles of progesterone during subsequent luteal phases. These results reconfirm the importance of the cyclooxygenase system in the mechanism of ovulation. It does not appear that follicular LTB4 is a key component in the processes of ovulation or luteinization in sheep.

The involvement of oxytocin in ovulation and in the outputs of cyclo-oxygenase and 5-lipoxygenase products from isolated rat ovaries

The effects on ovulation of a specific anti-oxytocin rabbit serum (anti-OT) (50.0 microliters) given by intrabursal injection into the right ovaries of etherized adult female rats at proestrus, were explored by counting the number of ovulated ova present within the right oviducts. Left ovaries were not treated and served as control ovaries. Control rats were treated with male normal rabbit serum (NRS) (50.0 microliters) given by intrabursal injections into the right ovaries of animals at proestrus. Ovulation was induced by injection of human chorionic gonadotrophin (hCG). Anti-OT administered into the right ovarian bursae of proestrous rat ovaries evoked a significant 51% inhibition of ovulation in comparison with that observed in control non-injected left ovaries (p less than 0.01). Also, when the ovulation of right ovaries injected with anti-OT was compared with that of left ovaries injected with NRS, the number of ovulated ova in the right side was significantly smaller (30%) than on the contralateral side (p less than 0.02). However, in rats pre-treated with hCG the intrabursal injection of oxytocin (OT) (50.0 mU/ml) into right and left ovaries failed to alter the number of ovulated ova compared with that of rats receiving intrabursal injections of saline. The basal control and the OT-evoked synthesis and release of endogenous prostaglandin E2 (PGE2) and PGF2 alpha were explored in ovaries isolated from prepuberal rats injected with pregnant mare's serum gonadotrophin (PMSG), two days prior to sacrifice. OT augmented the basal release of PGF2 alpha but did not influence that of PGE2. Moreover, the conversion of exogenous 14C-arachidonic acid (14C-AA) into different prostanoids and into 5-HETE, in the presence and in the absence of added OT (50.0 mU/ml), was studied in rat ovaries isolated in proestrus. The challenge with OT augmented the basal synthesis and release of PGF2 alpha and of 5-HETE from 14C-AA, but failed to influence the formation of products generated via the cyclo-oxygenase pathway, namely 6-keto-PGF1 alpha, PGE2 and thromboxane B2 (TXB2). Therefore, the present results suggest that ovarian OT may play a role in the ovulatory process, via generation of PGF2 alpha to enhance contractions of ovarian smooth muscle and of 5-HETE to promote follicular collagenolysis.

The involvement of platelet activating factor in ovulation

Follicle rupture during ovulation is associated with inflammation-like changes. Because platelet activating factor (PAF) participates in the inflammatory process, the effect of a PAF-specific antagonist, BN52021, on the ovulatory response was tested in rats. BN52021, administered locally, inhibited follicle rupture in rats stimulated to ovulate with human chorionic gonadotropin (hCG). In addition to suppressing rupture of the follicles, this antagonist suppressed the hCG-stimulated increase in ovarian collagenolysis and vascular permeability. The inhibition of ovulation of BN52021 could be reversed by simultaneous administration of PAF. Furthermore, PAF partially reversed the blockage of ovulation by inhibitors of eicosanoid synthesis. Collectively, these results suggest the involvement of PAF in ovulation. Its role seems to be closely related to the metabolism of arachidonic acid. Thus, modulation of PAF action may serve as an additional target for regulation of reproduction via its action on ovulation.

Ovarian effects of SK&F 86002-A2 in the rat: site of action

In a preliminary 30-day study, oral administration of SK&F 86002-A2, an inhibitor of prostaglandin and leukotriene synthesis, blocked ovulation and altered ovarian structure and hormone production in rats. The purpose of the present study was to determine if the locus of action of SK&F 86002-A2 for these effects was the ovary or some other site in the female reproductive system, using a number of experimental approaches. A single sc or intraovarian injection of SK&F 86002-A2 did not block spontaneous or gonadotropin-induced ovulation in proestrous rats, whereas indomethacin, a positive control, acutely disrupted the ovulatory process. Since neither route of administration blocked ovulation, integrated pituitary and ovarian events were not negatively affected by a single injection of SK&F 86002-A2 at doses which caused ovarian dysfunction when administered repeatedly for 30 days. In contrast to a single dose, oral administration of SK&F 86002-A2 to hypophysectomized rats for 2 weeks suppressed follicular growth and estradiol production in response to sc administration of pregnant mare serum gonadotropin. Although ovarian function was suppressed in hypophysectomized rats, LH surges induced by estradiol in ovariectomized rats were not affected by administration of SK&F 86002-A2 for 2 weeks. Thus, hypothalamic/pituitary dysfunction did not contribute to the ovarian effects of SK&F 86002 that occurred after repeated dosing. In conclusion, these results indicate that disruption of ovarian cycles by SK&F 86002-A2 is related to a direct effect on the ovary, and not to altered hypothalamic/pituitary function and LH release. Specifically, SK&F 86002-A2 may suppress the ovarian response to gonadotrophin, retarding follicular growth and estrogen production. The ovarian effects are consistent with a pharmacological expression of the inhibitory action of SK&F 86002-A2 on prostaglandin and leukotriene synthesis.

Ovarian effects of an anti-inflammatory-immunomodulatory drug in the rat

The purpose of this study was to determine whether a 30-day administration of SK&F 86002-A2, an inhibitor of cyclooxygenase and 5-lipoxygenase pathways of arachidonate metabolism, adversely affected reproductive cycles, ovarian structure, and/or pituitary/ovarian hormone secretion. Cyclooxygenase and 5-lipoxygenase enzymes catalyze the reactions leading to the synthesis of prostaglandins and leukotrienes, respectively, which are physiological regulators of ovarian function. Female rats were dosed once daily by gavage with 0, 1, 5, 10, 30, or 60 mg (base)/kg/day of SK&F 86002-A2 for 30 consecutive doses beginning on the day of vaginal proestrus. Vaginal smears were then examined daily until necropsy, when ovaries and uteri were collected for macroscopic and histological examination. In addition, serum concentrations of estradiol, progesterone, luteinizing hormone, follicle stimulating hormone, and prolactin were estimated by radioimmunoassay. Estrous cycle irregularity, resulting from a dose-related lengthening of the interestrous interval, significantly (p less than 0.05) reduced the number of cycles in rats receiving 60 mg/kg/day of SK&F 86002-A2 compared to controls. Furthermore, the ovaries from this group of rats weighed significantly more (p less than 0.05) than controls, apparently due to an increased occurrence of enlarged, cystic follicles that occasionally contained blood. Luteinized follicles with entrapped ova were also detected during histological examination. Dilatation of the uterine lumen was observed in some rats receiving doses of SK&F 86002-A2 greater than 1 mg/kg/day. Serum progesterone in rats receiving 60 mg/kg/day of SK&F 86002-A2 was significantly (p less than 0.05) lower than controls. In contrast, mean levels of serum estradiol were elevated in rats receiving 30 mg/kg/day of SK&F 86002-A2. Serum concentrations of FSH, LH, and prolactin were not significantly different in any group. The results of this study suggest that SK&F 86002-A2 disrupts cyclic ovarian function by a local, cumulative action that inhibits ovulation and alters steroid secretion.

Arachidonic acid oxidation by brain and placenta preparations from normal and placental insufficient fetal rabbit

Cytosolic (100,000 g) fractions of fetal rabbit brain and placenta tissue convert [1-14C]arachidonic acid into several oxidation products identified with the lipoxygenase [12-hydroxyeicosatetraenoic acid (12-HETE) and 15-HETE] and cyclooxygenase [prostaglandin E2 (PGE2)] pathways. Formation of 12-HETE and 15-HETE by fetal brain is time-dependent, reaching a plateau after 40 min and is linear with protein concentration. An apparent affinity constant of 0.06 mM and a Vmax of 0.1 mumol/h/g wet weight are presumably responsible for the excessive accumulation of 12-HETE and 15-HETE in comparison to PGE2 (Km = 0.5 mM). The latter is synthesized by the placenta particulate fraction but almost exclusively by the brain cytosol. Compared to brain, the activity of the placenta tissue is exceedingly higher and in addition to 12-HETE and 15-HETE there is a substantial formation of 12-L-hydroxyheptadecatrienic acid. Formation of 12-HETE and 15-HETE at 21 days is as effective as at 31 days gestation and is strongly inhibited by nordihydroguaiaretic acid (93%), BW755c (99%), and AA861 (84%) but not by indomethacin. Placenta and brain tissues of intrauterine growth retarded fetuses after ligation of placental blood vessels fail to convert arachidonic acid into other eicosanoids. Loss of enzymatic activity also observed in normal tissue after prolonged storage cannot be restored by the addition of several SH agents, ascorbate, or ferric iron.

Investigations on the control of in vitro spontaneous brook trout (Salvelinus fontinalis) ovulation

The possible roles of follicular cyclooxygenase and cAMP in the control of in vitro spontaneous brook trout (Salvelinus fontinalis) ovulation were investigated. Brook trout oocytes that had undergone germinal vesicle breakdown and follicular separation in vivo, were incubated in vitro in the presence of indomethacin. At 3 or 30 microM, indomethacin significantly reduced the levels of PGF and PGE (measured by radioimmunoassay) in the incubation medium but did not inhibit spontaneous ovulation in vitro. Follicular cAMP levels were measured by a competitive protein binding assay, prior to and during spontaneous ovulation. cAMP levels were approximately 3.2 pmol/mg protein prior to incubation and did not fluctuate significantly from this value throughout the 24-hr incubation period. The phosphodiesterase inhibitor, 3-isobutyl-l-methyl-xanthine, significantly increased follicular cAMP levels at 1.0 and 0.1 mM. The combined results suggest that cyclooxygenase metabolites or a decrease in cAMP are not involved in the control of spontaneous brook trout ovulation in vitro. The in vitro effects of primaquine, a putative phospholipase mediator, were also investigated. At lower concentrations (0.1-0.5 mM), primaquine significantly enhanced ovulation above that observed in spontaneous controls. However, at 1.0 mM, primaquine inhibited spontaneous ovulation. Indomethacin at 3 or 30 microM did not block the stimulatory effect of primaquine observed at lower concentrations, indicating that cyclooxygenase metabolites are not involved in the stimulatory effect of primaquine on ovulation.

Ovarian lipoxygenase activity and its regulation by gonadotropin in the rat

In our previous study a dose-dependent blockage of follicular rupture at ovulation by inhibitors of lipoxygenase was demonstrated. Here the presence of 5-lipoxygenase activity in the whole ovary and in the Graafian follicle is estimated by a chemiluminescence assay using unlabeled arachidonic acid as substrate in the presence of luminol and by conversion of 14C-arachidonic acid into lipoxygenase products as separated by HPLC. Both approaches demonstrated lipoxygenase activity in whole ovarian homogenates and in homogenates of preovulatory Graafian follicles. Furthermore, within 6 h after stimulation in vivo with hCG, lipoxygenase activity was increased by 2-fold in the whole ovarian homogenate and by 5-fold in the follicular homogenate. These results confirm the presence of lipoxygenase in rat ovaries, and its stimulation by gonadotropin and thus corroborate the suggested involvement of lipoxygenase products in follicular rupture at ovulation.

Cyclooxygenase and lipoxygenase pathways in the preimplantation rabbit uterus and blastocyst

We have measured by radioimmunoassay the concentration and production of 5(S)-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), a metabolite in the lipoxygenase pathway, and PGs in different uterine compartments, and blastocysts during the preimplantation period in the rabbit. The production is defined as the synthesis minus the metabolism for a defined period of time. The pattern of uterine PGF production on days 5-6.5 was quite similar for the whole uterus and the myometrium showing a peak production on Day 6. The concentration and production of PGF were always higher in the endometrium. While significant production of PGE was noticed in the whole uterus on days 5-6 and in the myometrium on Day 6, the endometrium showed some production on these days. On the contrary, absolutely no production of this PG was observed in the endometrium on Day 6.5. The concentration and production of 6-keto-PGF1 alpha were always lower in the endometrium than those observed in the myometrium or the whole uterus. While highest production of this PG was found to be on Day 6.5 in the whole uterus and on Day 5 in the endometrium, the production in the myometrium remained constant on all days examined. The production of 5-HETE in the endometrium was noticeable on Days 5-6.5, in the whole uterus on Days 5 and 6.5, and in the myometrium only on Day 6.5. However, the concentrations of 5-HETE showed a tendency to be higher at 2 h than at 0 h in these compartments on Days 5-6.5. Furthermore, a linear increase in 5-HETE levels both at 0 h and 2 h was observed in the endometrium on Days 5-6.5; no such difference in mean 5-HETE level was noted in the whole uterus or myometrium on any of these days. The production of 5-HETE in the blastocyst was noted only on Day 5. The results not only demonstrate the presence of both the cyclooxygenase and the lipoxygenase pathways in the preimplantation rabbit uterus and blastocyst, their differential operation in various compartments of the uterus on various days of early pregnancy suggests an integrated role for these mediators in embryo-uterine interaction during implantation.