Inhibition of ovulation in marmoset monkeys by indomethacin

Cyclooxygenase-2 and its role in ovulation: a 2004 account

The pre-ovulatory surge of gonadotrophins triggers a marked and obligatory increase in follicular prostaglandin synthesis prior to ovulation, and the cyclooxygenase (COX) enzyme is a key rate-limiting step in the biosynthesis of prostaglandins. In the early 1990s, the pre-ovulatory rise in follicular prostaglandin synthesis was shown to result from the selective induction of a novel COX isoform, now referred to as COX-2. Differences in the time-course of COX-2 induction in species with a short versus a long ovulatory process suggest that the enzyme could be a molecular determinant that sets the alarm of the mammalian ovulatory clock. Some of the fine molecular mechanisms involved in the transcriptional activation of the COX-2 gene in granulosa cells have also been elucidated. The binding of trans-activating upstream stimulatory factors (USF) to a consensus E-box cis-element in the proximal region of the promoter was shown to play a predominant role in COX-2 transcription. Studies showed that COX-2 expression could also serve as a valuable marker for follicular commitment to ovulation during hyperstimulatory cycles. This paper presents a comprehensive review of the events that led to the characterization of COX-2 in pre-ovulatory follicles, updates current concepts on the control of COX-2 expression in pre-ovulatory follicles, and addresses the consequences of COX-2 inhibition to women fertility and potential implications of COX-2 expression in ovarian cancer.

The effect of nonsteroidal anti-inflammatory drugs on ovulation: a prospective, randomized clinical trial

OBJECTIVE

To assess the effect of ibuprofen, a nonspecific inhibitor of prostaglandin synthesis, on ovulation.

DESIGN

Prospective, randomized, double-blind, placebo-controlled cross-over study.

SETTING

University Medical Center.

PATIENT(S)

Twelve normally cycling women between ages 20 and 40.

INTERVENTION(S)

Subjects were randomized to either oral ibuprofen (800 mg) or placebo three times per day, beginning when the maximum diameter of the leading follicle reached 16 mm by ultrasound, and continuing for 10 days total. The second cycle was a washout period, and in the third cycle, the subjects were crossed over to the alternate regimen from the first cycle. The probability of delayed follicular collapse was determined using the binomial distribution, and changes in P levels were compared using the paired t test.

MAIN OUTCOME MEASURE(S)

Urinary LH surge, follicular collapse by serial transvaginal ultrasonography, and serum midluteal P levels.

RESULT(S)

Eleven of 12 subjects detected an LH surge with both ibuprofen and placebo. Five of 11 women demonstrated a >or=2-day increase in time interval from detection of the LH surge to follicular collapse, and 3 of those 5 had been randomized to ibuprofen. This represents a 27% (3 of 11; 95% confidence limits: 1%, 53%) rate of delay for follicular collapse for ibuprofen. There was no difference in average midluteal P levels for ibuprofen or placebo.

CONCLUSION(S)

If ibuprofen inhibits follicular collapse, this effect is seen in a small group of study subjects, and this information should be clinically reassuring to patients who take nonsteroidal anti-inflammatory drugs. Serum midluteal P levels were unaffected by administration of ibuprofen.

Effects of systemic administration of indomethacin on ovulation, luteinization, and steroidogenesis in the rabbit ovary

Indomethacin blocks ovulation in human chorionic gonadotropin-stimulated rabbits. Experiments were done with an in vitro ovarian perfusion system to investigate whether indomethacin affects luteinization and steroidogenesis. Indomethacin (10 mg/kg) was administered in combination with human chorionic gonadotropin (100 IU) via a marginal ear vein, and a second dose of indomethacin was given 8 hours later. Control animals received vehicle in place of indomethacin. Laparotomy was performed 24 hours after the initial treatment. The presence of unruptured follicles and corpora lutea was recorded and the ovaries were perfused in vitro for 3 hours. Progesterone, prostaglandin F2 alpha, prostaglandin E2, and 6-keto-prostaglandin F1 alpha were measured in samples obtained at 0, 30, 60, 120, and 180 minutes from the circulating perfusion medium entering and exiting the ovary. At the end of the perfusion all ovaries (12 treated and 10 controls) were fixed for histologic analysis. Ovulation occurred in all control ovaries but in none of the indomethacin-treated ovaries. The mean number of unruptured follicles per ovary in the treated group was not significantly different from the number of corpora lutea plus unruptured follicles per ovary in the controls. Cells in both groups were qualitatively similar in ultrastructure; abundant lipid droplets, smooth endoplasmic reticulum, and mitochondria were seen. Secretion rates of progesterone and prostaglandin did not differ between the two groups during the 3-hour perfusion period. These results suggest that transformation of granulosa cells into fully functional luteal cells can occur in the absence of follicular rupture.

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)

Production of prostacyclin by different cell types of the goat ovary

A sensitive platelet aggregation-inhibition assay was used to quantitate the production of prostacyclin by different cell types of the goat ovary. The assay could detect as low as 0.16 ng in the test sample. Different cell types i.e. granulosa, theca and corpus luteum or the total ovarian homogenate were incubated at 37 degrees C for 10 minutes with or without 0.2mM arachidonic acid. Rat aortic strips were incubated under similar conditions as a positive control. Under basal conditions the amount of prostacyclin produced by corpus luteum cells was higher compared to that by granulosa cells. When the precursor of prostaglandins (arachidonic acid) was provided the production markedly increased in corpus luteum, granulosa, and ovarian homogenate as well as in aortic strips. Theca cells did not produce detectable levels of prostacyclin even when the precursor was provided. Trapidil did not alter the basal but enhanced the arachidonic acid-stimulated prostacyclin production in homogenate and granulosa cells with no further increase in corpus luteum cells. U-51605 decreased basal as well as arachidonic acid-stimulated prostacyclin production in all the cell types. The prostacyclin production in ovaries is compartmentalized suggesting a possible role in ovarian physiology.

Effect of aspirin on the luteal phase of human menstrual cycle

The effect of aspirin (acetylsalicylic acid) on the luteal phase length and function was studied in ten normal cycling women. They received three grams daily for twenty days starting from the fifth day of the cycle. Urinary pregnanediol-3 alpha-glucuronide (Pg-diol- 3G ) and luteinising hormone (LH) were assayed in daily early morning urine samples together with daily vaginal smear for cytohormonal evaluation. The excretion profile of Pg-diol- 3G and LH of another group of ten normal women were taken as controls. Aspirin caused shortening of both cycle length and luteal phase duration. Available evidence suggests the presence of corpus luteum deficiency in the treated cycles.

Anovulatory luteal cycles in primates

The short-term therapy with gonadotropins and inhibitors of prostaglandin synthesis was administered to 12 adult cycling cynomolgus monkeys to study morphology and functions of anovulatory luteinized follicles. In Group 1, five monkeys (6 cycles) received human menopausal gonadotropin (hMG 10 I.U. FSH/10 I.U. LH per 1 kg) on cycle day (c.d.) 5 and 6. Human chorionic gonadotropin (hCG 50 I.U. per 1 kg) and hMG (5 I.U. LH and 5 I.U. FSH per 1 kg) were given at 12:00 on c.d. 7. Indomethacin (15 mg/kg) was injected at 16:30 on c.d. 7 and 08:30 on c.d. 8. Ovarian biopsy was obtained in 2 cycles. In Group 2, 7 monkeys (33 cycles) received single injection of hCG (50 I.U./kg) and hMG (5 I.U. FSH/5 I.U. LH/kg) four to one days before the expected ovulation. Two doses of Naproxen-sodium were given orally 4 and 20 hours later. After treatment, females were kept with males for 5 to 7 days. Laparotomy was performed one week after treatment. Ovarian biopsy was obtained in 5 cycles. Treatment in the midfollicular phase caused premature luteinization of the follicles and suppression of ovulation in all cycles. Histological studies revealed presence of luteinized follicles. Serum progesterone was elevated. Luteal phase averaged 13.6 days (vs. 15.8 days in ovulatory cycles). Treatment in the late follicular phase resulted in luteinization of the dominant follicle and inhibition of ovulation in 20 (61%) cycles. Luteal phase lasted 17.1 days. Serum progesterone was elevated to low or midluteal values. Gross evidence of ovulation was present in 13 (39%) cycles. One pregnancy occurred. All monkeys returned to regular, ovulatory cycles after the experiments were terminated.

An ultrastructural study of ovarian perifollicular capillaries in the indomethacin-treated rabbit

The perifollicular capillaries of the rabbit ovary were observed by light and electron microscopy following administration of human chorionic gonadotropin (hCG) and indomethacin (IM). Fenestrations and interendothelial gaps were not observed at 4, 10, or 12 hours, at which times carbon particles were confined to capillary lumina. By 24 hours, dilated capillaries were noted among granulosa cells and theca. In the theca, interendothelial gaps permeable to carbon particles were observed. At 48 hours, ribosome-rich, newly developed capillaries were noted. Many collagen fibrils were observed in the tunica albuginea and theca externa in hCG/IM-treated rabbits in contrast to those treated with hCG alone. Ovarian prostaglandins normally produced in response to gonadotropins may be responsible for alterations in perifollicular capillaries and degradation of collagen in the follicle wall, changes considered essential for ovulation.

Clinical significance of the luteinized unruptured follicle syndrome as a cause of infertility

The luteinized unruptured follicle syndrome (LUF) exists and is cause of infertility. Although the data of the laparoscopic inspection of the ovaries and the corpora lutea and of steroid hormone concentrations in peritoneal fluid constitute strong evidence that the syndrome exists, its role as a cause of infertility is less clear. The only evidence available that the LUF syndrome is a cause of infertility, is the finding that the syndrome occurs statistically more frequently in women with unexplained infertility than in a control group of women. It still has to be proven whether the LUF syndrome occurs repetitively in each cycle and causes infertility, or whether the syndrome occurs intermittently and only reduces the probability of conception. Diagnosis of the syndrome can be made by laparoscopic inspection of the ovaries and by the assay of 17 beta-estradiol and progesterone, in peritoneal fluid between day 14 and 20 of the cycle. The relationship between the LUF syndrome and pelvic endometriosis and luteal phase insufficiency is discussed. We suggest that the LUF syndrome might be the cause of endometriosis thus explaining the statistical association between both syndromes, and the infertility of women with only mild endometriosis. We favor the hypothesis that the LUF syndrome might be caused by stress thus constituting a "psychological infertility" and we suggest that the syndrome could explain the spontaneous cure rate. Therefore, before any therapy can be accepted as the treatment of the LUF syndrome, it should be strictly assessed with adequate controls.

The effect of indomethacin on spontaneous and human menopausal gonadotropin induced pressure changes in the tissue and arterial vascular system from human ovaries perfused in vitro

Eight human ovaries were perfused in a closed recirculating system with a semisynthetic, hemoglobin-free medium. Arterial and intraovarian pressures were recorded simultaneously. In three experiments spontaneous pressure changes were noticed. In five experiments pressure changes were induced with human menopausal gonadotropin (hMG) (approximately 70mIU/ml follicle stimulating hormone (FSH) and 40mIU/ml luteotrophic hormone (LH) II. IRP-hMG). Frequency and amplitude of pressure changes in the arterial system and fluctuations in tissue pressure were reduced with indomethacin (20 micrograms/ml). In one experiment 40 micrograms/ml indomethacin had been used. In spite of the high dose of indomethacin arterial and tissue pressure changes were not abolished in all experiments. Therefore it is assumed that vascular and tissue activities are not mediated by prostaglandins only.

Ovum retention in the human

Two cases of ovum retention occurring in postovulatory follicles are described. The ova were recovered at laparoscopy by aspiration of decompressed ovulatory follicles, one during a natural cycle and the other following a programmed clomiphene/human chorionic gonadotropin cycle. Each patient had a normal luteal phase with an increased progesterone level indicative of ovulation. The implications of these findings and their relevance to human fertility studies are discussed.