| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
a Departments of Obstetrics and Gynecology and Physiology, Göteborg University, S-413 90 G;auoteborg, Sweden
b Department of Obstetrics and Gynecology, University of Utah, Salt Lake City, Utah 84132
c Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
NS-398 reduced the synthesis of PGE2 in isolated, LH-stimulated preovulatory follicles incubated in vitro. The inhibition by NS-398 was similar to that of indomethacin. Maximal inhibition was noted from 0.1 µM. Neither progesterone nor cAMP production was affected by NS-398 or indomethacin. The effect of in vivo administration of NS-398 (1, 3, or 10 mg/kg BW, s.c.) to proestrous rats 1 h after the injection of an ovulatory dose of hCG was monitored in follicles extirpated 10 h after hCG. These follicles were incubated in vitro, and NS-398 dose-dependently reduced PGE2 production. The synthesis of cAMP and progesterone was not altered. In separate experiments, the same doses of NS-398 were injected to determine their effect on ovulation in vivo. The number of ovulations was decreased by the highest dose of NS-398.
In the in vitro ovarian perfusion model, NS-398 (10 µM) reduced the number of ovulations initiated by LH and isobutylmethylxanthine. Lower doses of NS-398 (0.1 and 1 µM) were less effective. The production of prostanoids (PGE2, PGF2
, and 6-keto-PGF1) was reduced in a dose-dependent manner by NS-398. The secretion of steroids was not affected.
This study demonstrates that selective inhibition of PGS-2 by NS-398 reduces LH/hCG-stimulated production of prostanoids and the number of ovulations both in vivo and in vitro. These results provide direct evidence to strengthen the role of the inducible, granulosa cell-expressed PGS-2 as one of the key regulators in the ovulatory process and also document that the elevated and perhaps sustained levels of PG are obligatory for ovulation.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
are increased more than 30- and 6-fold, respectively, from the morning of proestrus to ovulation in the rat [7, 8]. Even though the active role of PG in the ovulatory process is well established, the nature of the ovulation-promoting effect of PG is not well understood. Vascular effects, such as vasodilatation, increased vascular permeability, and stimulation of collagen breakdown, have been suggested as possible mechanisms of action [9, 10]. Among other reported effects of PG related to microcirculation is their ability to induce neovascularization [11]. The key enzyme in the formation of prostanoids is prostaglandin endoperoxide G/H synthase (PGS), also known as cyclooxygenase [12]. This enzyme exists in at least two isoforms, PGS-1 [13] and PGS-2 [14]. PGS-1 is constitutively expressed in most cells, and the enzyme is involved in the synthesis of cytoprotective PG in various tissues [12]. The other isoform, PGS-2, is induced in macrophages and other cells stimulated with inflammatory mediators, including cytokines and mitogenic agents [12, 14]. In rat preovulatory (PO) follicles, PGS-1 is present mainly in the theca cells [15], whereas PGS-2 is rapidly induced in the granulosa cells in response to the ovulatory LH surge [16]. In bovine and equine PO follicles, the theca cells do not express PGS-1 [17, 18]. In these two species, PGS-2 is induced in the granulosa cells by the LH surge in a manner similar to that in the rat [17, 18]. PGS-2 is also present in freshly isolated human granulosa cells obtained from patients undergoing hormone treatment for in vitro fertilization [19].
Recently, several pharmacological inhibitors were developed in order to selectively inhibit PGS-2 for therapeutic use. One such inhibitor, [N-(2-cyclooxihexyloxy-4-nitrophenyl)]-amitanesulfonamid (NS-398), was demonstrated to have a high selectivity for PGS-2 in comparison to its effect on PGS-1 in vivo and in vitro [20–23]. Its effectiveness in reducing experimentally induced inflammatory reactions was comparable to the effects of indomethacin at equimolar concentrations [20–23]. Furthermore, NS-398 did not interfere with the synthesis of the PGS-1 or the PGS-2 enzymes [22]. Targeted disruption of the pgs-2 gene in mice results in renal dysfunction and female infertility due to impairment of the ovulatory process [24–26] and implantation [27]. Disruption of the pgs-1 gene did not result in an ovarian phenotype [28]. Interestingly, mice lacking the progesterone receptor (PR) also demonstrated an ovarian phenotype with inability to ovulate [29]. In the pgs-2 knock-out model, the levels of peripheral steroids have not been measured, and the responsiveness of follicles to gonadotropins has not been investigated [24, 25]. Furthermore, fetal and postnatal effects due to lack of PGS-2 in neuronal tissue [30] might interfere with the development of the pituitary-ovarian axis prior to puberty. The role of prostanoids in the regulation of ovarian-derived steroids and inhibin for the feedback regulation of gonadotropin-secretion has earlier been demonstrated in vivo in eCG-primed rats [31].
In the present study, we examined the acute effects of the inhibitor of PGS-2, NS-398, on the ovulatory process. The use of both in vivo and in vitro models enabled us to closely examine PG synthesis and relate changes in PG production to the number of ovulations. The effects of NS-398 were compared to those of the nonspecific PGS inhibitor indomethacin. Since earlier in vivo studies using either nonselective pharmacological blockers of prostanoid formation [31] or specific deletion of the prostanoid-synthesizing enzymes by gene targeting [24, 25] have reported "extraovarian" effects, a comparison of the in vivo and in vitro results obtained in the present study allowed us to more specifically determine the role of PGS-2 for the acute regulation of the ovulatory process in response to LH/hCG.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Immature Sprague-Dawley rats (BeeKay, Stockholm, Sweden; Harlan Co., Indianapolis, IN) were kept under controlled light conditions (14L:10D) with free access to food and water. All experiments were carried out according to the principles and procedures outlined in the NIH Guide and Use of Laboratory Animals.
Hormones and Chemicals
Ovine LH (NIADDK-oLH-26) was kindly provided by the NIADDK and National Hormone and Pituitary Program (Rockville, MD). Human CG was purchased from Serono (Rome, Italy) or Organon (West Orange, NJ). Equine CG, 3-isobutyl-1-methylxanthine (IBMX), and indomethacin were purchased from Sigma Chemical Company (St. Louis, MO). The supplier of Ketalar was Parke-Davis (Barcelona, Spain). Rompun was from Bayer (Leverkusen, Germany); Medium 199 and Dulbecco's Modified Eagle's medium/Nutrient Mix F12 (1:1) (DMEM-F12, 1:1), from Gibco (Gaithersburg, MD); gentamicin sulfate, from Biological Industries (Kibbutz Beit Haemek, Israel); BSA (fraction V), from Boehringer Mannheim (Mannheim, Germany); insulin, from Novo-Nordisk (Copenhagen, Denmark); heparin, from Lövens (Ballerup, Denmark). NS-398 was purchased from Cayman Chemical Company (Ann Arbor, MI).
Experimental Procedures
The numbers of experimental animals, ovaries, and oocytes retrieved from the oviducts are indicated in the figure legends.
I. Incubation of follicles in vitro and ovulation rate after exposure to PGS inhibitors in vivo Immature rats (27 days of age) were injected with 0.15 IU of hCG s.c. twice daily for 2 days to obtain PO follicles [32]. NS-398 and indomethacin were dissolved in dimethyl sulfoxide (stock solutions; 1 mg/ml). Follicles were isolated and incubated (3 follicles per vial) at 37°C for 5 h in medium alone (DMEM-F12, 1% fetal bovine serum; 0.5 ml) or in medium containing LH (0.5 µg/ml) and various concentrations of NS-398 or indomethacin (0.1, 1, 10 µM). The production of PGE2, cAMP, and progesterone was measured in the medium at the end of the incubation period. The measurements of PG were limited to PGE2 since previous studies [7, 8] have demonstrated that this is the major prostanoid produced by LH-stimulated PO follicles.
In another experimental setup, immature, hCG-primed rats received an ovulatory dose of hCG (10 IU i.p.) on the morning (0900 h) of Day 29 [33]. Aliquots of NS-398 were diluted in PBS containing 1% Tween 20 to obtain doses of 1, 3, and 10 mg/kg BW. These solutions (a total volume of 0.2 ml) were injected s.c. 1 h after hCG administration. Control animals received PBS containing 1% Tween 20 only. Ten hours after the injection of hCG, i.e., approximately 2 h prior to the expected time of ovulation, follicles were dissected free from adherent tissue under a stereomicroscope. These follicles (termed "ovulatory," 4–6 per ovary) were selected by their size and typical vascularization. No morphological difference was observed between the treatment groups. Follicles from the respective groups (3 follicles per vial) were incubated in medium (DMEM-F12, 1% fetal bovine serum; 150 µl) at 37°C for 2 h. The levels in the incubation medium of cAMP, progesterone, and PGE2 were measured. In separate experiments, the ovulation rate was estimated in groups of animals receiving the same treatment in vivo as above. The ovulation rate was calculated as the number of ovulated oocytes retrieved from the oviduct in the morning (0800–0900 h) on Day 30, i.e., 20 h after the ovulatory dose of hCG.
Follicles from the various treatment groups in vitro were examined for the presence of expansion of cumulus cells [34].
II. Effects of PGS inhibitors on steroidogenesis, PG production, and ovulation rate in the in vitro-perfused ovary In the morning of Day 27, immature rats were injected with eCG (15 IU) s.c.; 48 h later, the rats were anesthetized with a combination of Ketalar and Rompun (40 and 6.5 mg/kg BW, respectively). Heparin sulfate (300 IU) was injected into the femoral or tail vein. The right ovary was surgically isolated as previously described in detail [35].
The perfusions were performed in a recirculating system [35] containing 30 ml of medium (Medium 199 with Earle's salts supplemented with 50 µg/ml gentamycin sulfate, 0.2 IU/ml insulin, and 4% BSA). The ovaries were initially perfused for 1–2 h before the administration of LH (0.1 µg/ml) + IBMX (0.2 mM). Only the ovarian specimens, which maintained a flow rate between 0.7 and 1.3 ml/min during this period, at pressure of approximately 80 mmHg, were used in these experiments. NS-398 and indomethacin were diluted in ethanol and PBS containing 1% Tween 20. Various amounts of these stock solutions were added 30 min prior to LH+IBMX to obtain the concentrations indicated in Figure 3. The maximal volume of the vehicle (945 µl of ethanol/PBS/Tween 20) was added to one of the experimental groups (control). The perfusions were continued for up to 20 h. Samples of medium (1 ml) were taken at various time points during the perfusion (0, 1, 3, 5, 7, 10, and 20 h after LH) and replaced with equal amount of fresh medium. The samples were stored at -70°C. The ovulation rate was determined by counting the ovulated oocytes in the perfusion chamber [35].
Measurements of cAMP, Steroids, and PG in the Media
The levels of cAMP were determined in the incubation media as previously described [36]. Progesterone and estradiol were analyzed using RIAs as previously described [36]. PGE2, PGF2, and 6-keto-PGF1 were assayed either by using single antibodies, liquid phase, 3H-RIA as described previously [37] or, for incubation experiments, by ELISA kit (PGE2; Oxford Biochemical, Ann Arbor, MI).
Statistics
The results are presented as the mean ± SEM. Statistical differences were evaluated by Kruskal-Wallis rank test followed by Mann-Whitney U-test. A value of p < 0.05 was considered to be significant.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
PO follicles from hCG-primed rats were isolated and incubated with LH (0.5 µg/ml) for 5 h in order to compare the inhibitory effects of indomethacin and NS-398 on the synthesis of PG. LH significantly stimulated the production of PGE2 (1.23 ± 0.18 ng/ml) compared to that in follicles incubated in medium only (0.1 ± 0.001 ng/ml). NS-398 at a concentration of 0.1 µM or higher completely inhibited LH-stimulated PGE2 synthesis. The inhibition by NS-398 was as effective as that by indomethacin (Fig. 1a). LH-stimulated progesterone synthesis was not altered by NS-398 or indomethacin (Fig. 1b). Likewise the expansion of the cumulus cells by LH was not affected by the addition of NS-398 or indomethacin (data not shown).
|
Rats with PO follicles were injected s.c. with various doses (1, 3, and 10 mg/kg BW) of the inhibitor 1 h after an ovulatory dose of hCG to determine the in vivo effects of NS-398. The in vivo stimulation of cAMP and progesterone by hCG in incubated ovulatory follicles was not affected by NS-398 (data not shown). However, the synthesis of PGE2 was dose-dependently and significantly reduced by NS-398 (Fig. 2). In addition, the number of oocytes retrieved from the oviduct in animals receiving the same treatment was assessed the following morning (Fig. 2). In the control group, the ovulation number was 4.2 ± 0.9 per ovary. Rats treated with NS-398 at 1 and 3 mg/kg BW had a similar number of ovulations. However, the highest dose of NS-398 (10 mg/kg BW) resulted in a significant decrease in the ovulation rate (1.2 ± 1.0), although this dose did not completely suppress PG synthesis.
|
Effects of NS-398 on the Production of Prostanoids and Ovulation Rate in the In Vitro-Perfused Ovary
The levels of PGE2, PGF2, and 6-keto PGF1 in the perfusion media at 10 h and 20 h are presented in Figure 3. The three prostanoids were elevated at both 10 h and 20 h in the control group (LH+IBMX and vehicle). At 10 h, i.e., 2–3 h prior to the expected time of ovulation, all three prostanoids were in the same range, 14–26 ng/ml, in this group. The addition of indomethacin (0.1 µM) resulted in a significant decrease of PGE2, PGF2, and 6-keto-PGF1. The inhibition was most pronounced for PGF2. NS-398 at the lowest concentration (0.1 µM) had no significant effect on the levels of prostanoids compared to those in the control group. However, the two higher concentrations (1 and 10 µM) exerted a dose-dependent and significant reduction of all three prostanoids. NS-398 (1 and 10 µM) reduced PGE2 and PGF2 more than indomethacin (0.1 µM). Only the highest dose of NS-398 decreased 6-keto-PGF1 more than indomethacin did. At 20 h, the patterns of inhibition in response to NS-398 were similar to those obtained at 10 h. However, the levels of all three prostanoids were higher at the latter time point.
|
The concentrations of progesterone and estradiol in the perfusion media were measured at various time points throughout the perfusion periods. There were no significant differences between the control group and groups receiving NS-398 or indomethacin (data not shown).
The ovulation rates of the in vitro-perfused ovaries are summarized in Figure 4. All ovaries ovulated in response to LH+IBMX (control). The addition of indomethacin (0.1 µM) reduced the number of ovulations. The lower doses of NS-398 (0.1 and 1 µM) did not significantly decrease ovulation rate compared to that in the control group. However, the highest dose of NS-398 (10 µM) resulted in a significant reduction of the ovulation rate, similar to the effect of indomethacin.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
The key role of PG in the ovulatory process has been demonstrated in several species [2]. The hormone- and cell-specific regulation of the inducible form of PGS, PGS-2, in PO granulosa cells by LH/hCG has further strengthened the role of prostanoids [15, 16, 33, 38] in this process. Recent studies with gene targeting of the two isoforms of PGS resulted in an ovarian phenotype with impaired ovulation only when PGS-2 was deleted [24, 25]. Absence of PGS-1 did not affect ovarian function [28], specifically ovulation. In the present study, the aim was to selectively inhibit the PGS-2 enzyme during the period from the LH surge to ovulation. Earlier in vivo studies using either nonselective pharmacological blockers of prostanoid formation [31] or specific deletion of the prostanoid-synthesizing enzymes by gene targeting [24, 25] have reported extraovarian effects. A comparison of the in vivo and in vitro results obtained in the present study allowed us to more specifically determine the role of PGS-2 for the acute regulation of the ovulatory process in response to LH/hCG.
The PGS-2 inhibitor NS-398 was demonstrated to be an effective blocker of prostanoid synthesis both in vivo and in vitro. Furthermore, the inhibition of PG production did not alter cAMP synthesis, steroidogenesis, or cumulus expansion. This indicates specific site(s) of action for PG that are distinct from the effects of steroids in the ovulatory process [39, 40] and the cellular response to LH, e.g., luteinization [41] and cumulus expansion [42].
Three different doses of NS-398 were used in the in vivo experiments. This resulted in a dose-dependent reduction in the synthesis of PGE2 in ovulatory follicles. The highest dose used in the present study (10 mg/kg BW) has been reported to completely inhibit the formation of PGE2 and 6-keto-PGF1 synthesis in carrageenan-air-pouch inflammation in the rat [20] and the production of PGE2 and PGF2 in the brain cortex of the newborn pig [30]. In the present in vivo experiments, NS-398 was administered 1 h after hCG, i.e., 10–11 h prior to the expected time of ovulation. This resulted in a reduction of PGE2 synthesis 9–10 h later and demonstrated that prostanoid production was reduced but not completely blocked during the critical interval 2–3 h prior to ovulation reported earlier [43, 44]. A reduction of PG synthesis was also observed in the in vitro perfusion system both at 10 h and at 20 h, demonstrating the effectiveness of these inhibitors during the entire ovulatory period. It was recently suggested that the time interval between the induction of PGS-2 and follicular rupture is critical for the ovulatory process, since this period of approximately 10 h is constant in rats [16, 35], cows [17], and horses [18]. A single dose of the compound (10 mg/kg BW, i.e., identical to highest dose in the present study) effectively inhibited the inflammatory response to carrageenan in rats for as long as 24 h [20].
The inhibitory effect of NS-398 on prostanoid synthesis and ovulation rate in the in vitro perfusion system was in accordance with the in vivo results. The synthesis of PGE2, PGF2, and 6-keto-PGF1 was reduced in a dose-dependent manner with the highest dose (10 µM) of NS-398 and was associated with a significant reduction in the number of ovulated oocytes.
Although the two lower doses of NS-398 also reduced the synthesis of PGE2, only the highest dose of NS-398 decreased the number of ovulations. A similar relationship was reported for indomethacin [44] in a study in which higher doses were required to block ovulation in the rat whereas lower doses effectively reduced PG synthesis. Earlier studies have demonstrated an effect on the lipoxygenase pathway by indomethacin [44]. This effect was also reported to be more closely correlated to the impairment of ovulations than the inhibition of PG synthesis [44]. Such an effect of NS-398 on the lipoxygenase pathway is less likely, since the compound has not been reported to interfere with the production of leukotrienes (LT) [22]. In fact, the highest dose of NS-398 used in the present study in vitro (10 µM) had no effect on the ovarian levels of LTB4 or LTC4/D4/E4 measured at 10 h after LH+IBMX (data not shown).
Another aspect of the action of indomethacin may be its nonspecific interference with calcium ions in diverse biological processes [45]. Thus, the fact that indomethacin and NS-398 presented different potencies in relation to PG synthesis may be explained by interference with calcium-regulated events in the ovulatory follicle, e.g., granulocyte degranulation, antagonism of histamine-action, and inhibition of smooth muscle response [45]. Recently, it was demonstrated that high doses of indomethacin that inhibited both PG production and ovulation in the ewe also affected intracellular levels of calcium in follicular cells [46]. This latter study also illustrated that the inhibition of follicular rupture required a higher dose of indomethacin compared to the dose resulting in a reduction of PG levels, similar to what was observed for NS-398 in the present study. This difference in inhibition of PG synthesis and impairment of the ovulatory process could be due to several factors. First, the results suggest that prostanoids must be reduced below a &;" level in order to prevent ovulation. In addition, there might be a critical time period for this reduction, and Espey and coworkers reported [43] a defined time interval for the administration of indomethacin in order to inhibit ovulation in the rabbit in vivo. Other examples of threshold are the differentiated cellular responses to the changes in secretory pattern for the gonadotropins during the follicular and luteal phases [47]. The determinants of this threshold and the duration of PG synthesis are probably a result of the fine-tuned interplay of cellular events initiated by LH, e.g., the production of progesterone and the appearance of the PR [48] during a narrow time interval. Further studies are needed to elucidate the intracellular events regulated by prostanoids in the PO follicle.
Although indomethacin and NS-398 exerted similar effects in the present study, a difference in potency in relation to the reduction of PG synthesis and ovulation was noted. This could be attributable to several factors. First, indomethacin could interfere with additional processes in the ovulatory cascade. In a previous in vivo study [40], indomethacin was reported to reduce the activities of both the ovarian kallikrein and plasminogen activator system. Secondly, the affinity and mode of action of indomethacin to the two isoforms of PGS might differ from that of NS-398. The cell-specific localization of PGS-1 and PGS-2 to theca and granulosa cells, respectively, in the ovulatory follicle might also contribute to the observed differences between the compounds. Interestingly, a dual peak of PG synthesis was reported for the rabbit ovary in vivo [43]. The early peak, which appeared approximately 2 h after hCG, i.e., prior to induction of PGS-2 [16], might be due to an increased activity by PGS-1. However, isolated rat PO follicles stimulated by LH in vitro did not demonstrate a similar early rise in PG synthesis [49]. Although the PGS-1 knock-out mice did not show an ovarian phenotype [28], further studies are needed to determine the role(s) of the two isoforms in follicular function. Indomethacin inhibits both PGS-2 and PGS-1 in a time-dependent, irreversible manner in in vitro assays with purified PGS enzymes [50]. In contrast, NS-398 is a time-dependent, irreversible inhibitor of PGS-2, whereas the compound forms a time-independent and reversible complex with PGS-1. Since the PGS-2 protein is rapidly turned over in vivo (t1/2 = 4 h) [51], NS-398 may effectively inhibit the enzyme for its entire lifetime. Interference with the synthesis of PGS-2 is less likely, since neither indomethacin nor NS-398 has been demonstrated to affect transcriptional or translational regulation of PGS-2 [52]. This is in contrast to glucocorticoids (such as dexamethasone), which mainly affect the transcription of the PGS-2 gene [51, 53]. However, whether such differences observed with purified enzymes can be applied to the complex situation in biological systems remains to be determined.
The importance of different inflammatory-related mechanisms for ovulation, besides prostanoid production, have been illustrated in several studies [10]. In the present study, the results from the in vivo and the in vitro experiments were similar, demonstrating that they can be generalized to the ovulatory process per se and are not related to differing experimental conditions. Both the in vivo and in vitro experiments demonstrated that PG production was dose-dependently reduced by NS-398. Neither of the compounds could completely block the ovulatory process, and earlier studies using higher concentrations of indomethacin have reported similar findings [6, 44]. Even in mice lacking the pgs-2 gene, a limited number of ovulations do occur [26]. This supports the view of additional pathways of importance for the regulation of the follicular rupture, e.g., transcriptional regulators such as the progesterone receptor [29] and C/EBPß [54, 55].
In summary, these in vivo and in vitro results further strengthen the hypothesis that inducible, granulosa cell-expressed PGS-2 is one of the key regulators in the ovulatory process. Selective inhibition of the inducible, granulosa cell-expressed PGS-2 enzyme resulted in a dose-dependent reduction of prostanoids and an inhibition of ovulation in the rat. The incomplete linkage between inhibition of prostanoid synthesis and a reduction in ovulation rate may be explained by a failure of PGS-2 inhibition to affect alternative pathways such as steroids, leukotrienes, kallikrienes, and/or plasminogen activator activities.
|
FOOTNOTES |
|---|
2 Correspondence: Lars Hedin, Department of Physiology, Göteborg University, Medicinaregatan 1F, S-413 90 Göteborg, Sweden. FAX: 46 31 773 3531; lars.hedin{at}fysiologi.gu.se
Accepted: June 22, 1998.
Received: December 17, 1997.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
receptor expression by interleukin-1ß in cultured human granulosa-luteal cells. Endocrinology 1997; 138:3628–3644.This article has been cited by other articles:
|
|
 |
|
  Q. Li, F. Jimenez-Krassel, J. J Ireland, and G. W Smith Gene expression profiling of bovine preovulatory follicles: gonadotropin surge and prostanoid-dependent up-regulation of genes potentially linked to the ovulatory process Reproduction, February 1, 2009; 137(2): 297 - 307. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Kurusu, M. Jinno, H. Ehara, T. Yonezawa, and M. Kawaminami Inhibition of ovulation by a lipoxygenase inhibitor involves reduced cyclooxygenase-2 expression and prostaglandin E2 production in gonadotropin-primed immature rats Reproduction, January 1, 2009; 137(1): 59 - 66. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Sayasith, N. Bouchard, M. Dore, and J. Sirois Regulation of Bovine Tumor Necrosis Factor-{alpha}-Induced Protein 6 in Ovarian Follicles during the Ovulatory Process and Promoter Activation in Granulosa Cells Endocrinology, December 1, 2008; 149(12): 6213 - 6225. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. L. Russell and R. L. Robker Molecular mechanisms of ovulation: co-ordination through the cumulus complex Hum. Reprod. Update, May 1, 2007; 13(3): 289 - 312. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Q. Li, F. Jimenez-Krassel, A. Bettegowda, J. J Ireland, and G. W Smith Evidence that the preovulatory rise in intrafollicular progesterone may not be required for ovulation in cattle J. Endocrinol., March 1, 2007; 192(3): 473 - 483. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M Gaytan, C Bellido, C Morales, J E Sanchez-Criado, and F Gaytan Effects of selective inhibition of cyclooxygenase and lipooxygenase pathways in follicle rupture and ovulation in the rat. Reproduction, October 1, 2006; 132(4): 571 - 577. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Bridges, C. M. Komar, and J. E. Fortune Gonadotropin-Induced Expression of Messenger Ribonucleic Acid for Cyclooxygenase-2 and Production of Prostaglandins E and F2{alpha} in Bovine Preovulatory Follicles Are Regulated by the Progesterone Receptor Endocrinology, October 1, 2006; 147(10): 4713 - 4722. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Hernandez-Gonzalez, I. Gonzalez-Robayna, M. Shimada, C. M. Wayne, S. A. Ochsner, L. White, and J. S. Richards Gene Expression Profiles of Cumulus Cell Oocyte Complexes during Ovulation Reveal Cumulus Cells Express Neuronal and Immune-Related Genes: Does this Expand Their Role in the Ovulation Process? Mol. Endocrinol., June 1, 2006; 20(6): 1300 - 1321. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Q. Li, F. Jimenez-Krassel, Y. Kobayashi, J. J Ireland, and G. W Smith Effect of intrafollicular indomethacin injection on gonadotropin surge-induced expression of select extracellular matrix degrading enzymes and their inhibitors in bovine preovulatory follicles. Reproduction, March 1, 2006; 131(3): 533 - 543. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Dahm-Kahler, C. Lofman, R. Fujii, M. Axelsson, P. O. Janson, and M. Brannstrom An intravital microscopy method permitting continuous long-term observations of ovulation in vivo in the rabbit Hum. Reprod., March 1, 2006; 21(3): 624 - 631. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. El-Nefiawy, K. Abdel-Hakim, and N. Kanayama The selective prostaglandin EP4 agonist, APS-999 Na, induces follicular growth and maturation in the rat ovary Eur. J. Endocrinol., February 1, 2005; 152(2): 315 - 323. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Sirois, K. Sayasith, K. A. Brown, A. E. Stock, N. Bouchard, and M. Dore Cyclooxygenase-2 and its role in ovulation: a 2004 account Hum. Reprod. Update, September 1, 2004; 10(5): 373 - 385. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. W. Peters, J. R. Pursley, and G. W. Smith Inhibition of intrafollicular PGE2 synthesis and ovulation following ultrasound-mediated intrafollicular injection of the selective cyclooxygenase-2 inhibitor NS-398 in cattle J Anim Sci, June 1, 2004; 82(6): 1656 - 1662. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Sayasith, N. Bouchard, M. Sawadogo, J. G. Lussier, and J. Sirois Molecular Characterization and Role of Bovine Upstream Stimulatory Factor 1 and 2 in the Regulation of the Prostaglandin G/H Synthase-2 Promoter in Granulosa Cells J. Biol. Chem., February 20, 2004; 279(8): 6327 - 6336. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Sakurai, K. Tamura, S. Okamoto, T. Hara, and H. Kogo Possible Role of Cyclooxygenase II in the Acquisition of Ovarian Luteal Function in Rodents Biol Reprod, September 1, 2003; 69(3): 835 - 842. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Gaytan, C. Bellido, M. Gaytan, C. Morales, and J. E. Sanchez-Criado Differential Effects of RU486 and Indomethacin on Follicle Rupture During the Ovulatory Process in the Rat Biol Reprod, July 1, 2003; 69(1): 99 - 105. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Segi, K. Haraguchi, Y. Sugimoto, M. Tsuji, H. Tsunekawa, S. Tamba, K. Tsuboi, S. Tanaka, and A. Ichikawa Expression of Messenger RNA for Prostaglandin E Receptor Subtypes EP4/EP2 and Cyclooxygenase Isozymes in Mouse Periovulatory Follicles and Oviducts During Superovulation Biol Reprod, March 1, 2003; 68(3): 804 - 811. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Patino, G. Yoshizaki, D. Bolamba, and P. Thomas Role of Arachidonic Acid and Protein Kinase C During Maturation-Inducing Hormone-Dependent Meiotic Resumption and Ovulation in Ovarian Follicles of Atlantic Croaker Biol Reprod, February 1, 2003; 68(2): 516 - 523. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Duffy and R. L. Stouffer Follicular administration of a cyclooxygenase inhibitor can prevent oocyte release without alteration of normal luteal function in rhesus monkeys Hum. Reprod., November 1, 2002; 17(11): 2825 - 2831. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y.-L. Wu and M. C. Wiltbank Transcriptional Regulation of the Cyclooxygenase-2 Gene Changes from Protein Kinase (PK) A- to PKC-Dependence after Luteinization of Granulosa Cells Biol Reprod, May 1, 2002; 66(5): 1505 - 1514. [Abstract] [Full Text]
|
|
|
|
 |
|
 D. M. Duffy and R. L. Stouffer The ovulatory gonadotrophin surge stimulates cyclooxygenase expression and prostaglandin production by the monkey follicle Mol. Hum. Reprod., August 1, 2001; 7(8): 731 - 739. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Pall, B. E. Friden, and M. Brannstrom Induction of delayed follicular rupture in the human by the selective COX-2 inhibitor rofecoxib: a randomized double-blind study Hum. Reprod., July 1, 2001; 16(7): 1323 - 1328. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Pall, M. Mikuni, K. Mitsube, and M. Brännström Time-Dependent Ovulation Inhibition of a Selective Progesterone-Receptor Antagonist (Org 31710) and Effects on Ovulatory Mediators in the In Vitro Perfused Rat Ovary Biol Reprod, December 1, 2000; 63(6): 1642 - 1647. [Abstract] [Full Text]
|
|
|
|
 |
|
 J. A. Elvin, C. Yan, and M. M. Matzuk Growth differentiation factor-9 stimulates progesterone synthesis in granulosa cells via a prostaglandin E2/EP2 receptor pathway PNAS, August 10, 2000; (2000) 180295197. [Abstract] [Full Text]
|
|
|
|
|
|
F. Filion, N. Bouchard, A. K. Goff, J. G. Lussier, and J. Sirois Molecular Cloning and Induction of Bovine Prostaglandin E Synthase by Gonadotropins in Ovarian Follicles Prior to Ovulation in Vivo J. Biol. Chem., August 31, 2001; 276(36): 34323 - 34330. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. L. Robker, D. L. Russell, L. L. Espey, J. P. Lydon, B. W. O'Malley, and J. S. Richards Progesterone-regulated genes in the ovulation process: ADAMTS-1 and cathepsin L proteases PNAS, April 25, 2000; 97(9): 4689 - 4694. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Elvin, C. Yan, and M. M. Matzuk Growth differentiation factor-9 stimulates progesterone synthesis in granulosa cells via a prostaglandin E2/EP2 receptor pathway PNAS, August 29, 2000; 97(18): 10288 - 10293. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
