The stimulation of prostaglandin production by two antiprogesterone steroids in human endometrial cells

Lipopolysaccharide-induced murine embryonic resorption involves nitric oxide-mediated inhibition of the NAD+-dependent 15-hydroxyprostaglandin dehydrogenase

The initial inactivation of prostaglandins (PGs) is mediated by 15-hydroxyprostaglandin dehydrogenase (15-PGDH). PGs are potent mediators of several biological processes, including inflammation and reproduction. In uterus, PGs play a key role in infection-induced pregnancy loss, in which concentration of this mediator increased. This process is accompanied with the induction of nitric oxide synthase expression and a marked increase in uterine levels of nitric oxide. There is no information concerning nitric oxide contribution to potential changes in PG catabolism, but experimental evidence suggests that nitric oxide modulates PG pathways. The specific objectives of the study were to evaluate the protein expression of HPGD (15-PGDH) and to characterize the nitric oxide-dependent regulation of this enzyme in a model of lipopolysaccharide (LPS)-induced embryonic resorption. Results show that LPS decreased HPGD protein expression and augmented PGE synthase activity; therefore, PGE2 levels increased in uterus in this inflammatory condition. Just as LPS, the treatment with a nitric oxide donor diminished HPGD protein expression in uterine tissue. In contrast, the inhibition of nitric oxide synthesis both in control and in LPS-treated mice increased 15-PGDH levels. Also, we have found that this enzyme and PGE2 levels are not modulated by peroxynitrite, an oxidant agent derived from nitric oxide. This study suggests that LPS and nitric oxide promote a decrease in the ability of the uterus for PG catabolism during bacterially triggered pregnancy loss in mice.

The relationship between the production and the anti-gonadotrophic action of prostaglandin F 2 alpha in luteal cells from the marmoset monkey (Callithrix jacchus) in the early and mid-luteal phase

To address the potential luteolytic role for prostaglandin F(2 alpha) (PGF(2 alpha)) in the corpus luteum of the common marmoset monkey (Callithrix jacchus), the ability of marmoset luteal cells, maintained in monolayer culture, to produce PGF(2 alpha) was determined in vitro in the presence and absence of human chorionic gonadotrophin (hCG) and other established pharmacological modulators of PGF(2 alpha) synthesis. We also assessed the effects of the PGF(2 alpha) analogue, cloprostenol, on progesterone output from luteal cells isolated in the early luteal phase versus the mid-luteal phase (days 3 and 14 post ovulation, respectively). Cloprostenol had no effect on progesterone output from luteal cells isolated on day 3 of the luteal phase, whereas it significantly inhibited both basal and hCG-stimulated progesterone synthesis by day 14 luteal cells during the culture period 48-72 h (P<0.001). Intra-luteal PGF(2 alpha) concentrations were 5-fold higher in luteal cells isolated in the early luteal phase than in mid-luteal phase cells (16.5+/-3.5 versus 3.5+/-0.6 pmol/10(5) cells). While PGF(2 alpha) production was unaffected by hCG in vitro, it was decreased by indomethacin (1000 ng/ml) (P<0.05) and stimulated by the calcium ionophore A23187 (10 micromol/l) (P<0.05) in luteal cells from both stages of the luteal phase. Phospholipase A(2) did not influence PGF(2 alpha) production by day 3 luteal cells whereas at 10 IU/ml, it significantly stimulated PGF(2 alpha) production by day 14 luteal cells (P<0.05). Hence, the timing of luteolysis in the common marmoset monkey appears to involve changes in both the luteal cell response to and production of PGF(2 alpha).

Antifertility effects of antigestogens

Since the discovery of the structure and function of steroids over 60 years ago, it has long been recognized that synthetic antagonists of the natural hormones would have potential therapeutic uses. Antagonists of mineralocorticoids, androgens and oestrogens, for example spironolactine, cyproterone, flutamide and tamoxifen, have already found a place in the management of hormone dependent conditions. In 1982, chemists at Roussel UCLAF announced that they had synthesized mifepristone (RU486) 17β-hydroxy-11(p-(dimethylamino)phenyl)-17-(1-propynyl) estra-411, 9-dien-3-one) a derivative of norethindrone which had potent antiprogestogenic as well as antiglucocorticoid activity. Although it was immediately realised that this compound would potentially have wide clinical application, its development in the last 10 years has been dominated by its abortifacient action. In the original clinical report by Herrman and colleagues it was shown that bleeding occurred when it was given to female volunteers in the second half of the menstrual cycle. In addition, complete abortion occurred in eight of 11 women who took the drug in the early weeks of pregnancy. These findings, which demonstrated that mifepristone could be used as the basis of a medical method of inducing abortion, were immediately made the focus of groups opposed to abortion on moral grounds. Experience over the last 10 years has confirmed the promise of these early studies and mifepristone, in combination with a suitable prostaglandin, is now licensed in France, UK and Sweden for use as a medical method of inducing abortion in early pregnancy.

Role for prostaglandins in the regulation of type 1 11beta-hydroxysteroid dehydrogenase in human granulosa-lutein cells

11beta-hydroxysteroid dehydrogenase (11betaHSD) enzymes regulate glucocorticoid availability in target tissues. 11betaHSD1 is the predominant isoenzyme expressed and active in human granulosa-lutein (hGL) cells. This study investigated the effects of pharmacological inhibitors of prostaglandin (PG) synthesis on 11betaHSD1 activities and expression in hGL cells. The consequences for 11betaHSD1 of increasing exposure of hGL cells to PGs, either by treatment with exogenous PGs or by challenging cells with IL-1beta, were also assessed. Suppression of basal PG synthesis using four different inhibitors of PG H synthase enzymes [indomethacin, niflumic acid, meclofenamic acid (MA) and N-(2-cyclohexyloxy-4-nitorophenyl) methane sulfonamide (NS-398)] each resulted in significant decreases in both cortisol oxidation and cortisone reduction. Both activities of 11betaHSD1 were suppressed by up to 64+/-6% (P<0.05). Over 4 and 24 h, neither MA nor NS-398 affected the expression of 11betaHSD1 protein, suggesting enzyme regulation by PGs at the posttranslational level. When cells were cotreated for 4 h with PGHS inhibitors plus 30 nm PGD2, PGF2alpha, or PGE2, each PG overcame the suppression of cortisol oxidation by indomethacin or MA. Treatment of hGL cells with IL-1beta increased the concentrations of both PGE2 and PGF2alpha, accompanied by a 70+/-25% increase in net cortisol oxidation. All three responses to IL-1beta were abolished when cells were cotreated with MA. These findings suggest a role for PGs in the posttranslational regulation of 11betaHSD1 activities in hGL cells.

Mifepristone-induced vaginal bleeding is associated with increased immunostaining for cyclooxygenase-2 and decrease in prostaglandin dehydrogenase in luteal phase endometrium

The mechanism of mifepristone-induced vaginal bleeding and endometrial shedding was investigated in 13 women who took 200 mg mifepristone in the midluteal phase on d 8 after the onset of the urinary LH surge (LH+8). Endometrial biopsies were collected, 6-24 h after mifepristone (group 1, n = 7) or 36-48 h after mifepristone (group 2, n = 6), and compared with those from a control group in the midluteal phase (n = 7). All women reported vaginal bleeding commencing 36-48 h after taking mifepristone. Treatment with mifepristone significantly reduced serum progesterone levels in all women, when compared with the controls (13.2 nM vs. 34.8 nM, P = 0.001). After mifepristone, a significant increase in cyclooxygenase-2 immunoreactivity was apparent at 36-48 h (P = 0.0018), whereas prostaglandin 15 dehydrogenase enzyme-positive immunostaining declined, to be virtually absent by 36-48 h in both glands and in stroma (P < 0.05). There was no change in intensity or distribution of staining for steroid receptors after mifepristone. The changes in immunostaining for cyclooxygenase-2 and prostaglandin 15 dehydrogenase strongly support the hypothesis that an increase in the local concentration of prostaglandins in the endometrium is involved in the mechanism of bleeding induced by mifepristone in the luteal phase.

Inhibition of progesterone secretion with trilostane for mid-trimester termination of pregnancy: randomized controlled trials

BACKGROUND

Progesterone is central to the maintenance of pregnancy, and is thus the ideal target for fertility regulation. Two mechanisms by which progesterone can be targeted are: receptor blockade and reduction of progesterone production through enzyme inhibition. Mifepristone, a receptor blocker, is usually given as 'pretreatment' prior to prostaglandin administration in mid-trimester termination of pregnancy (TOP). Unfortunately, there are difficulties accessing mifepristone in developing countries, and TOP is therefore performed using prostaglandins alone, which results in unacceptably long induction-to-abortion intervals. Trilostane is a 3beta-hydroxysteroid dehydrogenase inhibitor which reduces progesterone production. In these mid-trimester studies it is evaluated as a method of pretreatment prior to misoprostol administration.

METHODS

Three consecutive randomized controlled trials comparing different trilostane regimens for pretreatment were performed. In study 1, trilostane was compared with placebo; in study 2, two doses of trilostane were compared (1080 mg and 720 mg); in study 3, the effect of adding danazol to trilostane as combination therapy was evaluated. The primary outcome in all the studies was the induction-to-abortion interval. Serum progesterone, estradiol and cortisol were measured serially during treatment.

RESULTS

In study 1, 48 women were randomized. The median induction-to-abortion interval was 9 h in the trilostane group and 18.5 h in the placebo group (P < 0.0001). Progesterone and estradiol production was significantly reduced in the women receiving trilostane, with maintenance of diurnal cortisol variation. Twenty-eight women were randomized in study 2, which demonstrated that there was no significant difference in the induction-to-abortion interval using 1080 mg and 720 mg trilostane when compared with the higher doses used in study 1. Study 3, in which 40 women were included, failed to show any additional benefit using combination therapy with danazol and trilostane.

CONCLUSIONS

Trilostane is an effective pretreatment agent in mid-trimester TOP.

Matrix metalloproteinase expression in Macaca mulatta endometrium: evidence for zone-specific regulatory tissue gradients

Matrix metalloproteinases (MMPs) are highly expressed in the human endometrium during menstruation, and these enzymes participate in the cyclic destruction and regeneration characteristic of the primate endometrium. To examine hormonal regulation of MMPs in vivo, we evaluated MMP expression and localization in the endometrium of ovariectomized rhesus macaques under various hormonal conditions. Although all MMPs were up-regulated by progesterone (P4) withdrawal, their expression declined spontaneously after menstruation in the absence of P4. Of 7 MMPs examined, only matrilysin and stromelysin-3 were suppressed any further when P4 levels were experimentally re-elevated. MMP expression was confined to the upper functionalis zone during menstruation, but after menstrual breakdown was complete, matrilysin and the tissue inhibitor of MMPs, TIMP-1, shifted expression from the functionalis to the basalis zone in the absence of both estradiol and P4. The spiral arteries in the functionalis, but not the basalis, were intense foci of MMP and TIMP-1 expression. Menstruation and MMP expression after P4 withdrawal were similar in both the presence and absence of estradiol. In sum, endometrial MMPs in vivo are strongly up-regulated by P4 withdrawal, but zone-specific tissue gradients greatly influence the pattern and degree of MMP expression.

Antinidatory effect of luteal phase administration of mifepristone (RU486) is associated with changes in endometrial prostaglandins during the implantation window

Luteal phase administration of mifepristone provides a significant degree of pregnancy protection to monkeys and women. Among several proposed mediators of the antinidatory action of luteal phase mifepristone, prostaglandins (PG) at the endometrial level appear important, and was examined in the present study using the rhesus monkey as the primate model. To this end, the concentrations of PGE2 and PGF2 alpha in endometrium and the profiles of cyclooxygenase (COX) and 15-hydroxy prostaglandin dehydrogenase (PGDH) were examined in untreated control animals, in animals subjected to mifepristone treatment (2 mg/day) alone or along with diclofenac (25 mg/day), or along with a PGE1 analog (100 micrograms misoprostol), in animals subjected to diclofenac alone treatment, and in animals treated with misoprostol alone on cycle days 16, 17, and 18. Tissue samples were collected on day 20 of treatment cycles from animals with discernible corpora lutea. Early luteal phase treatment with diclofenac did not result in any remarkable change in endometrial prostaglandin concentrations, however, there was an increase in the profile of COX. Animals exposed to misoprostol in the prereceptive stage, on the other hand, exhibited decreased expression of endometrial COX. The concentrations of PGF2 alpha and PGE2, as well as the ratios of PGF2 alpha to PGE2 concentrations, were increased along with a decrease in COX and PGD in endometrial samples following luteal phase mifepristone treatment. Although the underlying cellular mechanism of regulation of COX and PGDH in mifepistone-treated endometrium remains to be examined, the decrease in PG catabolism through low PGDH may contribute to the increased PG and high ratio of PGF2 alpha to PGE2 in mifepristone-exposed endometrium. It is plausible that mifepristone action on endometrial cells is mediated by an altered ratio of PGF2 alpha to PGE2. Furthermore, it appears that the regulation of PG milieu by COX and PGDH activities in reproductive tissues is under complex regulatory mechanism and is temporarily correlated with specific developmental events.

Differential effects of dexamethasone and RU 486, an antigestagen and antiglucocorticoid, on progesterone and relaxin secretion in hysterectomized pigs with aging corpora lutea

Pregnancy lasts about 114 days in pigs. Porcine corpora lutea produce not only progesterone but also relaxin (RLX), a peptide hormone that plays a critical role in suppressing uterine motility during pregnancy and in remodelling connective tissues in preparation for imminent parturition. Progesterone concentrations in peripheral blood remain elevated (approximately equal to 25 ng ml-1) for the major part of pregnancy and decrease just before parturition. The decrease in progesterone coincides with the peak prepartum RLX release. Glucocorticoid or antiglucocorticosteroid steroid, RU 486, administration during late pregnancy can induce parturition in the pig. Peak release of RLX and a coincident decrease of progesterone in the circulating blood can also occur in the complete absence of fetuses and uterus in the pig. The effects of glucocorticoid or antiglucocorticoidsteroid administration to such hysterectomized pigs on the secretion of RLX and progesterone were examined in this experiment. Unmated Yorkshire gilts were hysterectomized on days 6-8 (estrus = day 0) and given dexamethasone (total of 30 mg day-1; 2 times i.m. at 0800 and 1600 h) from days 110-118; control animals received vehicle injection during this period. RU 486 (4 mg kg1 body weight) was orally administered once daily (days 111-115) at 0800 h; placebo-treated controls were given the same amount of feed without the drug at this time. RLX concentrations in blood were markedly suppressed (P < 0.01) during dexamethasone treatment (3 +/- 0.9 ng ml-1; mean +/- S.E.) whereas a peak release of RLX (17 +/- 2.8 ng ml-1) occurred in the control group on day 113. In contrast, progesterone concentrations (14 +/- 2.5 ng ml-1) were unaffected by dexamethasone treatment compared with the controls (15 +/- 2.0 ng ml-1; P > 0.82). Upon withdrawal of dexamethasone on day 118, RLX plasma concentrations began to increase and peaked at 14 +/- 2.1 ng ml-1 (P < 0.01) on day 120. In contrast, the antiglucocorticosteroid given to hysterectomized pigs bearing aging corpora lutea caused a marked elevation in circulating levels of progesterone and delayed RLX release until after the end of drug treatment on day 115. Average weights of corpora lutea collected at day 12 were similar between treated and control groups (427 +/- 7 vs. 433 +/- 6 mg; P > 0.68). Results indicate that a synthetic glucocorticoid, dexamethasone, suppresses RLX secretion without causing luteolysis and such suppression is reversible; progesterone secretion remained unaffected. In contrast, the antiglucocorticoid, RU 486, raised progesterone plasma concentration and delayed RLX peak release but did not suppress it during treatment. This experiment provides further evidence that relaxin and progesterone secretion from aging corpora lutea of pigs are regulated through separate mechanisms, and adrenal glucocorticoids may be involved in such a regulation process.

Effect of mifepristone and antiestrogens on uterine PGF2 alpha and PGE2 concentrations in ovariectomized and pregnant rats

Four antiestrogens (anordiol, tamoxifen, RU 39411, ICI 182780) and the antiprogestin, mifepristone (RU 486), were administered to the following three animal models: (1) ovariectomized rats, (2) mated rats treated post-coitally; and (3) pregnant rats treated post-implantation. The antiestrogens were administered alone or in combination with mifepristone at doses effective in preventing and/or terminating pregnancy in rats. The objective of the study was to determine whether these drugs influenced uterine concentrations of prostaglandins (PGF2 alpha and PGE2). Antiestrogens administered alone to ovariectomized rats did not effect uterine PGE2 or PGF2 alpha concentrations; whereas the combination of anordiol/mifepristone increased uterine PGF2 alpha concentration, resulting in an increase in the PGF2 alpha/PGE2 ratio. Mated rats were treated post-coitally for three consecutive days with anordiol, tamoxifen, estradiol and mifepristone alone and with the combination of anordiol/mifepristone and tamoxifen/mifepristone. An increase in uterine PGF2 alpha concentrations and in the PGF2 alpha/PGF2 ratio occurred only in anordiol/mifepristone treated group. A decrease in uterine PGE2 concentrations occurred in animals treated with anordiol, tamoxifen and estradiol, resulting in an increase in the PGF2 alpha/PGE2 ratio. Anordiol (5.0 mg/kg/day) and mifepristone (4.0 mg/kg/day) alone and the combination of anordiol/mifepristone (2.5/1.0 mg/kg/day) administered to pregnant rats on day 7, 8 and 9 of pregnancy induced an increase in PGF2 alpha levels without affecting uterine PGE2 concentration. The changes in PGF2 alpha concentrations induced by anordiol and the combination of anordiol/mifepristone resulted in an increase in the PGF2 alpha/PGE2 ratio. The antiestrogens tested except for ICI 182780 possessed agonist activity when assayed by measuring their capacity to increase the uterine weights in ovariectomized rats. Also, ICI 182789 was the only antiestrogen that did not influence uterine PG concentrations. It can be concluded that ICI 182780 is the only "pure" antiestrogen among those tested. The present results show that antiestrogens and the combination of mifepristone plus anordiol at doses preventing implantation and terminating pregnancy increase uterine PGF2 alpha and/or decrease PGE2 concentrations, resulting in an alteration of PGF2 alpha/PGE2 ratio. These findings suggest that there exists a critical balance of PGF2 alpha to PGE2 concentrations in the uterus required for the normal passage of fertilized ova through the oviduct, initiating implantation of the blastocysts, development of embryos, and maintenance of pregnancy.

Anti-implantation activity of luteal phase mifepristone administration is not mimicked by prostaglandin synthesis inhibitor or prostaglandin analogue in the rhesus monkey

The use of mifepristone as an anti-implantation agent in the primate has been explored in the rhesus monkey with two specific aims: (i) to determine the contraceptive efficacy of very low-dose mifepristone administered on mated cycle days 16, 17, and 18; and (ii) to test the hypothesis that alteration in endometrial prostaglandin milieu by using either prostaglandin analogue or prostaglandin synthesis inhibitor can intervene the antifertility effect induced by mifepristone. Thirty female monkeys were randomly assigned to one of the six treatment groups. Five monkeys in the control group (group 1) were subjected to mating during cycle days 8-22. Four out of five monkeys became pregnant in the first mated cycle (80%) with detection of serum mCG by 12.7 +/- 1.5 days after ovulation. In group 2, 12 mated cycles were studied in five monkeys, mifepristone [RU486, 2 mg/day/animal, s.c. in 1 ml vehicle (1:4, benzyl benzoate:olive oil, v/v)] was given on cycle days 16, 17, and 18. In this group, no pregnancy was observed, thus providing complete pregnancy protection. Though there was an apparent extension of treatment cycle lengths in five cases with no incidence of inter-menstrual bleeding or spotting, there were no significant changes in serum estradiol (E) and progesterone (P). In group 3, four monkeys received prostaglandin (PG) synthesis inhibitor, diclofenac sodium (D, 25 mg/day/animal, i.m.) on cycle days 16, 17, and 18 in seven ovulatory menstrual cycles. Four of these cycles (57%) resulted in normal pregnancies; however, mCG detection (16.8 +/- 1.2 days after ovulation) was significantly (p < 0.05) delayed as compared to group 1. In group 4, four monkeys received 100 micrograms misoprostol (M), a PGE1 analogue, by gavage on mated cycle days 16, 17, and 18. Four pregnancies occurred in five treatment cycles (80%) with normal profiles of serum E and Pi mCG was first detected 13.2 +/- 1.7 days after ovulation. In group 5, seven monkeys received same dosages of RU486 and D on mated cycle days 16, 17, and 18. One hundred percent pregnancy protection was observed with luteal phase lengthening in eight treatment cycles but with unaltered E and P profiles. In group 6, five monkeys in nine treatment cycles received same dosages of RU486 and M on mated cycle days 16, 17, and 18. One pregnancy occurred; evaluation of E and P levels showed that the drug was given in the preovulatory period, which delayed ovulation and implantation, as mCG was detected 19 days post-ovulation. A delay in vaginal bleeding was observed in four treatment cycles with unaltered E and P profiles. Low-dose mifepristone appears to be a potential candidate for luteal phase and post-coital emergency contraception. However, the hypothesis that altered endometrial prostaglandin milieu may be responsible for mediating the anti-implantation effect of RU486 does not appear to be tenable based on our results in the rhesus monkey.

Differential release of prostaglandins by organ cultures of human fetal trachea and lung

Human fetal lung at 16-19 weeks gestation has a partially differentiated epithelium, and in organ culture, distal airsacs dilate and the epithelium autodifferentiates to type I and II pneumatocytes, processes regulated by endogenous prostaglandin PGE2. Human fetal trachea, at the same gestation, has a terminally differentiated mucociliary epithelium but after 4-6 d in organ culture, develops squamous metaplasia. Tracheal cultures restricted to 3 d have normal phase-contrast and light microscopy appearances and immunohistochemical reactivities (epithelium: cytokeratin 7,8,18; glutathione S-transferase pi-isozyme; epithelial membrane antigen and mesenchyme; desmin; vimentin). In human fetal trachea organ cultures, the predominant prostaglandins released are 6-keto-PGF1 alpha, PGF2 alpha, and PGE2, a pattern similar to that previously described for human adult trachea and lung. In fetal lung cultures, 13,14-dihydro-15-keto-PGF2 alpha is the major prostaglandin released with lesser amounts of 13,14-dihydro-15-keto-PFG2 alpha,PGF2 alpha,PGE2, and 6-keto-PGF1 alpha. Human fetal lung in vitro has the competence to self-differentiate, as early as 12 weeks gestation and presence of high levels in fetal lung of the inactive metabolite 13,14-dihydro-15-keto-PGE2 relative to PGE2 suggests that active prostaglandin catabolism may be one of the mechanisms to retard this stage of maturation in vivo by limiting PGE2 availability. Surprisingly, the profile of prostaglandins released from fetal lung organ culture does not change to that of a mature lung with terminal differentiation of the epithelium, and this may indicate differences in the expression of key prostaglandin-metabolizing enzymes in developing human fetal lung in culture and with in utero ontogeny.

Angiogenic activity in normal and dysfunctional uterine bleeding human endometrium; as measured by the chick chorioallantoic membrane assay

The modified chick chorioallantoic membrane assay was used to measure the angiogenic activity of whole human endometrium, endometrial gland and endometrial stromal cell preparations. Specimens were studied from normal subjects and from those suffering from dysfunctional uterine bleeding. This was done in order to investigate possible sites of angiogenic factor synthesis in endometrium. Significant angiogenic activity was demonstrated in all three sites and was present in all phases of the cycle except for the late secretory phase specimens. In the late secretory phase, compared to the controls, there was no significant angiogenic activity in the whole endometrial, endometrial gland nor endometrial stromal cell preparations. There were no differences in angiogenic activities between the various phases studied apart from a significant decrease in angiogenic activity for the endometrial gland cell preparations between the midsecretory phase and the late secretory phase. This study suggests than human endometrium produces local angiogenic factors throughout the menstrual cycle and that these factors may decrease towards the end of the cycle. It has been suggested that dysfunctional uterine bleeding may be due to disturbances in local angiogenic factors produced in the endometrium. This study found no significant differences in angiogenic activities between normal endometrium and dysfunctional endometrium. This suggests that dysfunctional uterine bleeding may not be due to disturbances in local angiogenic factors.

Effects of mifepristone and progesterone on collagen synthesis in the human uterine cervix

Antiprogestins are used to induce first trimester abortion and to dilate the cervix before vacuum aspiration. Cervical dilatation is associated with profound changes in the connective tissue. In what respect antiprogestins interfere with this process has hitherto been sparsely investigated. The aim of present study was to examine the influence of the antiprogestin mifepristone on cervical collagen synthesis in nonpregnant, early and late pregnant women. The effects were compared with those of progesterone. The content of collagen in cervical tissue was determined by measuring hydroxyproline. Collagen synthesis was studied in vitro either by incubation of cervical tissue specimens from women, pretreated with mifepristone in vivo, in the presence of 14C-proline or by incubation of cervical tissue of not pretreated women in the presence of the isotope and mifepristone or progesterone. Pretreatment with mifepristone, but not progesterone, induced a significant increase in cervical dilatation. The cervical concentration of collagen was not altered after mifepristone administration. Pretreatment with mifepristone did not quantitatively influence the time course of radiolabeling in vitro or the pattern of radiolabeling in different protein components as revealed by electrophoresis. In vitro mifepristone, like progesterone, reduced the incorporation of 14C-proline. From the present data we conclude that mifepristone pretreatment in connection with first trimester abortion is not associated with any major changes, qualitatively or quantitatively, of collagen synthesis. However, we cannot exclude that mifepristone still may affect the de novo formation of collagen since mifepristone, administered in vitro, did reduce collagen synthesis.

Cervical mucus concentration of prostaglandins E2 and F2 alpha after pretreatment with mifepristone in the first trimester of pregnancy

Cervical dilatation and softening after pretreatment with mifepristone are well documented. As this effect is similar to that observed after local application of prostaglandin E2 (PGE2) it is tempting to speculate that the effect of mifepristone is mediated via an increase of the endogenous secretion of prostaglandins from the cervical mucosa. Eighteen healthy women in the first trimester of pregnancy were treated with oral mifepristone (200 mg) 48 and 24 hours before legal abortion by vacuum aspiration and 18 women in the same age of gestation without any pretreatment served as controls. Cervical mucus was collected for measurement of prostaglandins by radioimmunoassay before administration of the drug and in connection with vacuum aspiration. The cervical dilatation at the time of surgery was significantly increased in women given mifepristone as compared with untreated women (7.6 versus 5.8 mm). The wet weight of collected cervical mucus was significantly increased in mifepristone treated women. The amount of PGE2 and prostaglandin F2 alpha per sample was unchanged in mifepristone-treated women, whereas the concentration was lower as an effect of dilution due to an increased yield in cervical secretion observed after mifepristone treatment. The present observation does not give any support to the hypothesis that mifepristone-induced cervical maturation is mediated via an increase in cervical prostaglandin production.

Prostaglandins and progesterone receptor antagonists in human fertility regulation

Anti-progesterone medicines have now been extensively studied for human fertility regulation. The combination of the anti-progesterone Mifepristone with prostaglandin analogues such as Gemeprost and Misoprostol have been used in several European centres for medical abortion. Used before nine weeks gestation, these medicines have similar efficacy to surgical abortion. In addition, administration of progesterone antagonists within five days of unprotected intercourse appear effective in pregnancy prevention. Anti-progesterone medicines are not currently available in Australia. The introduction of progesterone receptor antagonists and modern prostaglandins would save approximately $10,000,000 per year to the Australian Health Budget. Furthermore, the introduction of progesterone receptor antagonists for emergency contraception would have even greater financial and emotional savings for Australian women. In Australia, when known carcinogens can be purchased over the counter, it is surely time for Australians to consider effective emergency contraception bought over the counter.

Cervical smooth muscle contractile activity after treatment with mifepristone and progesterone

Contractile activity of the uterine cervix in vitro was studied in women pretreated with mifepristone 200 m chi 2 or progesterone suppositories 100 mg before cervical dilatation and vacuum aspiration in the first trimester. Mifepristone increased the dilatation of the cervix as measured prior to operation whereas progesterone had no effect. Spontaneous muscle activity and contraction frequency were not affected by either drug. Neither the inhibitory response to PGE2 nor the excitatory response to noradrenaline were significantly different from that in placebo-treated women. It is concluded that the cervical smooth muscle has no major role in the dilatatory effect of mifepristone in the cervical canal.

Prostaglandin production and metabolism in self-differentiating human fetal lung organ culture

PGE2 and PGF2 alpha are released into the media of human fetal lung organ cultures in decreasing amounts with time. This decline in PGs is not due to culture failure or loss of synthetic capacity, which can be stimulated by fetal bovine serum, nor is it due to increased catabolism of PGE2 to 13,14-dihydro-15-keto-PGE2 (PGEM) or of PGF2 alpha to 13,14-dihydro-15-keto-PGF2 alpha (PGFM). Immunohistochemically reactive PGs are not retained within lung cells. Antisera against methyl-moximated derivatives of PGEM or PGFM and preceded by derivatization on tissue sections of PGs by methyl-moximation not only demonstrate the localization of PGEM and PGFM in epithelial cells and blood vessels, but also show an overall decline in immunoreactivity with time. In addition electron microscopy of uncultured fetal lung removed directly after termination reveals various degrees of mitochondrial damage and in some cases plasma membrane blebs which resolve during the period in culture and as fetal lung self-differentiates. It is proposed that oxidative and mechanical stresses, occurring during termination of pregnancy or tissue preparation, result in cell damage and increased lung prostaglandin production, which, although decreasing during culture as cells recover, is sufficient to trigger terminal self-differentiation.

Prostaglandins and the cervix

The dramatic capabilities of prostaglandins to modify the condition of the uterine cervix have been exploited to the considerable benefit of patients who require therapeutic interventions for labour induction and termination of pregnancy. This will continue to be an important facet of clinical obstetric and gynaecologic practice, although further refinements and improvements in techniques seem certain to continue.

Production of 12-hydroxyeicosatetraenoic acid in early pregnant uterine cervix--lack of correlation to mifepristone-induced cervical ripening. A double-blind randomized biomechanical and biochemical study

The regulation of cervical ripening in pregnancy may involve arachidonic acid metabolites. We studied the formation of lipoxygenase products in cervical biopsies from twenty nulliparous women requesting a first trimester abortion. The patients were randomly allocated to receive either 100 mg of the progesterone antagonist mifepristone (RU 486) or placebo 48 and 36 hours before surgery. A capacity to produce significant amounts of 12-HETE and material co-chromatographing with leukotrienes was observed in the cervical tissue. No qualitative or quantitative relationship to mifepristone-induced cervical ripening was found. Although our data suggest a large variation of 12-HETE production it remains to clarify its role in the cervix.

Prostaglandins PGE2 and PGF2 alpha in human fetal lung: immunohistochemistry and release from organ culture

Immunohistochemical studies in human fetal lung have shown that epithelial and endothelial cells are both strongly and equally reactive for PGE2. In contrast, epithelial PGF2 alpha reactivity varied between fetuses, in some as intense as endothelial staining and in others very much less. As lung organ cultures differentiated, the intensity of PGE2 staining declined in airways and blood vessels, although it was still weakly positive at 10 days. In contrast, epithelial cells rapidly became negative for PGF2 alpha, whereas PGF2 alpha positivity was retained in blood vessels, albeit less obviously. PGF2 alpha and PGE2 were released into the media of organ cultures in decreasing amounts as cultures progressed. Amounts of released PGF2 alpha were greater by 2- to 10-fold than PGE2. Our findings suggest that the endogenous production of prostaglandins by human fetal lung in organ culture has a key role in the self-differentiation process that occurs in the absence of sera or added growth factors or hormones.

Cervical softening with mifepristone (RU 486) after pretreatment with naproxen. A double-blind randomized study

Pretreatment with the progesterone antagonist mifepristone reduces the stiffness and facilitates mechanical dilatation of the uterine cervix. We studied the influence of the cyclo-oxygenase inhibitor naproxen on the softening effect of mifepristone on the cervix in thirty nulliparae. The patients were randomly allocated to receive 500 mg naproxen (group A) or placebo (group B) orally 60, 48, 36, 24 and 12 hours prior to vacuum aspiration. All patients received 100 mg mifepristone 48 and 36 hours before surgery. We found that the cervical softening effect of mifepristone was not antagonized by naproxen. The study indicates that the effect of mifepristone on the early pregnant cervix is not mediated through an increased production of prostaglandins.

Uterine production of prostaglandins F2 alpha and 6-keto-F1 alpha by ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn

Ovariectomized early pregnant rats given continuous steroid replacement therapy have been treated with antiprogesterone steroid, ZK98299 or RU38486. At 24 h following treatment, uterine explants in culture were found to produce significantly greater amounts of PGF2 alpha, but not of 6-keto-PGF1 alpha, when compared to controls. ZK98299 and RU38486 gave almost identical levels of uterine PG production. The 6-keto-PGF1 alpha/PGF2 alpha production ratio for uteri of treated rats was decreased by 45% relative to controls. Similar changes in uterine PGF2 alpha production and 6-keto-PGF1 alpha/PGF2 alpha ratio have been shown for ovariectomized early pregnant rats in which progesterone has been withdrawn when compared to control animals. It has been suggested that inhibiting or withdrawing progesterone in rat uteri exposed to estradiol and progesterone may lead to a stimulation of endoperoxide F-reductase and/or E2 9-ketoreductase activities. The presence of luminal fluid in the uteri was observed for animals treated with antiprogesterone steroid or in which progesterone had been withdrawn. This was associated with a decrease in % dry weight for the uteri of these animals.

Mifepristone (RU486) alone or in combination with a prostaglandin analogue for termination of early pregnancy: a review

The availability of a medical mode of termination of early pregnancy by the administration of RU486, an antiprogesterone alone, or in combination with one of the PG analogues significantly reduces the maternal morbidity and mortality associated with the classical surgical abortion. RU486 given alone in early pregnancy induces complete abortion in 60% to 85% of cases, and when combined with prostaglandin analogues, gemeprost or sulprostone, reaches a success rate of 95% to 99%. RU486 may also be of potential value in the medical treatment of ectopic pregnancy. Its use as a postcoital contraception is suggested, but further research is required to determine whether RU486 can be used on a once-a-month basis for contraception.

Prostaglandin E and E2 alpha secretion by glandular and stromal cells of the pig endometrium in vitro: effects of estradiol-17 beta, progesterone, and day of pregnancy

Prostaglandins (PGs) are believed to play important roles in the establishment of pregnancy. Glandular and stromal cells were isolated from pig endometrium on days 11 through 19 of pregnancy and cultured in the presence of estradiol-17 beta (E2) and progesterone (P4) to determine the effect of day of pregnancy and steroids on the secretion of PGE and PGF2 alpha. Estradiol at concentrations between .01 and 1 microM did not affect PGE and PGF2 alpha secretion into the medium by glandular and stromal cells. Progesterone (.1 microM) suppressed (P less than .001) PGE and PGF2 alpha production from both cell types. Glandular cells secreted more (P less than .01) PGF2 alpha than PGE, whereas stromal cells collected on days 11, 12, 13, and 19 secreted more (P less than .05) PGE than PGF2 alpha. Stromal cells isolated from tissues collected on day 13 of pregnancy produced PGs with higher (P less than .01) PGE:PGF2 alpha ratio than those from tissues harvested on other days of pregnancy. Glandular cells isolated from tissues collected on days 13 and 19 and stromal cells isolated from tissue collected on day 13 of pregnancy secreted more (P less than .05) PGE and PGF2 alpha than cells isolated on other days of pregnancy. We conclude that: 1) P4 has a suppressing effect on PG secretion; 2) endometrial glandular and stromal cells each produce a unique profile of PGs; and 3) endometrial cells harvested on different days of pregnancy secrete different amounts of PGE and PGF2 alpha.

Effects of mifepristone in vivo on decidual prostaglandin synthesis and metabolism

Mifepristone is an effective abortifacient in combination with an exogenous prostaglandin but its mechanism of action is unknown. Mifepristone stimulates prostaglandin production from decidua in tissue culture. To determine whether this effect also operates in vivo, we treated women with mifepristone 24, 36 and 48 hours prior to surgical termination. Decidua was removed at operation and the ability of the tissue to generate prostaglandin in culture subsequently assessed. Pretreatment with mifepristone 36 hours prior to termination of pregnancy resulted in an increased production of PGF2 alpha in tissue culture (p less than 0.01). A significant decrease in PGFM production was seen 24 hours after pretreatment with mifepristone in vivo (p less than 0.01). These results suggest that the increased uterine activity observed after administration of mifepristone may be due to stimulation of endogenous prostaglandin production and inhibition of prostaglandin metabolism.

Self-differentiation of human fetal lung organ culture: the role of prostaglandins PGE2 and PGF2 alpha

Addition of PGE2, but not PGF2 alpha, to fetal lung organ cultures accelerates the process of self-differentiation with increased dilatation of terminal airsacs and differentiation of the epithelial lining. Indomethacin reduces the endogenous production by organ cultures of PGE2, PGF2 alpha, 13,14-dihydro-15-keto-PGE2, and 13,14-dihydro-15-keto-PGF2 alpha and retards the process of self-differentiation. Prolonged exposure of cultures to indomethacin results in cell necrosis. Indomethacin inhibition of self-differentiation can be reversed and accelerated by the addition of PGE2. Addition of PGF2 alpha in the presence of indomethacin prevents indomethacin-associated cell necrosis but does not accelerate dilatation or differentiation beyond that of cultures in sera-free media without additions. We propose that the endogenous production of PGE2 is a key process in the mechanism of self-differentiation of human fetal lung in organ culture.

The mechanisms of action of progesterone and the anti-progestin ZK 98734 on PGF2 alpha synthesis by early human decidua

The inhibition of prostaglandin (PG) synthesis found in early human decidua is antagonized by the anti-progestin, ZK 98734. This action of ZK 98734 is abolished by actinomycin, an inhibitor of protein synthesis and by the calcium channel blocker, verapamil. Calmidazolium, an antagonist of the intracellular calcium binding protein calmodulin was less effective in inhibiting the stimulation of PG synthesis induced by the anti-progestin. Chronic stimulation of protein kinase C activity by 1-oleoyl-2-acetyl-sn-glycerol (OAG) induced a slight reduction of PG release and was antagonized by polymixin. These findings suggest that inhibition of PG synthesis in early pregnancy is caused by progesterone and that increased release of PGs induced by anti-progestins is dependent on new protein formation and requires extracellular calcium.

Antiprogestagenic inhibition of uterine prostaglandin inactivation: a permissive mechanism for uterine stimulation

The use of antiprogestins as abortifacients is more effective when antiprogestin priming is followed by the administration of a small dose of synthetic prostaglandin. This increased myometrial sensitivity towards PG has not been explained and experiments in the guinea-pig where no myometrial activity is observed after 48 h of antiprogestin administration together with measurements of PG metabolites in uterine vein blood have given rise to the suggestion that prostaglandin synthesis is inhibited by antiprogestins. We have treated groups of 50 day pregnant guinea-pigs with 10 mg RU486 or vehicle alone and examined the ability of homogenised uterine tissues (myometrium/decidua, cervix, chorion and amnion) to metabolize PGE when given a large excess of substrate and sufficient cofactors. In addition we have examined the ability of these homogenates to synthesis PG. Antiprogestin treatment in vivo resulted in a 9-fold reduction in metabolic activity in chorion (P less than 0.02) and a 4-fold reduction in myometrium/decidua (P less than 0.02). Reduction in activity seen in amnion and cervix was not significant. The maximum metabolism was seen in the chorion and minimal metabolism in the amnion. Maximum PG production was seen in the amnion and minimum in the chorion. These results show that the effect of antiprogestin in reducing prostaglandin catabolism would reduce the threshold above which PG production would cause contractions which would in turn stimulate PG production. Thus an explanation is provided of how low doses of exogenous PGs or transient synthesis of endogenous PG within an antiprogestin treated uterus can led to a self sustaining cycle of stimulation which will lead to abortion.

Regulation of non-pregnant human uterine contractility. Effect of antihormones

Uterine contractility was recorded on cycle day LH+6 to LH+8 in a control and treatment cycle in 14 healthy non-pregnant volunteers. In the treatment cycle the subjects received either 50 mg of the antiprogestin RU 486 daily for three days or 40 mg of the anti-estrogen tamoxifen daily for two days. The treatment started on day LH+2. During the recording, 2 to 5 micrograms PGF2 alpha was administered into the uterine cavity. The plasma levels of progesterone and estrogen were the same in both the control and treatment cycles. RU 486 caused a significant increase in uterine contractility expressed in Montevideo Units (MU) and a decrease in uterine tonus in comparison with corresponding data obtained in the control cycle. Following treatment with tamoxifen, uterine contractility was lower but the difference was not significant. PGF2 alpha invariably caused a stimulation of uterine contractility. However, treatment with the antihormones did not influence the response. The result of the present study indicates that the change in uterine contractility occurring in the latter part of the menstrual cycle and during menstruation is due to progesterone withdrawal.

Comparison of antiprogestin stimulation of uterine prostaglandin synthesis in vitro

Progesterone has an inhibitory effect on prostaglandin synthesis in urine tissue and this effect is reversible with progesterone receptor antagonists. Although antiprogesterone steroids such as RU486 (Mifepristone) are effective at inducing abortion in women they have an improved efficacy when used with exogenous synthetic prostaglandin. In the guinea-pig such antagonists sensitize the uterus but do not result in increased myometrial activity and therefore may not induce endogenous PG synthesis. In this study the effects of antiprogestins on a preparation of rat uterus perifused with progesterone were studied. ZK98 734 caused a rapid and sustained increase in 6-oxoPGF synthesis which rose within the first 90 minutes. This rapid response suggested that some mechanism other than the induction of fresh protein synthesis was involved. A similar increase was not seen with pregnant guinea-pig myometrium/decidua perifused in a similar manner, suggesting that some other mechanism was responsible for the relatively low PG production in pregnancy. However increases in 6-oxoPGF in response to antiprogestins were recorded when pregnant guinea-pig decidua/myometrium was incubated for 4 hours. In these experiments 1 microM ZK98 734 and 1 microM ZK98 299 (Onapristone) gave a 2.7 fold increase in PG production whereas RU486 gave a 1.6 fold increase. Both 1 microM ZK98 734 and 1 microM ZK98 299 also gave a significant increase in PGE production but no increase in PGF was observed. These findings suggest that some antiprogestins might have a better effect on the stimulation of endogenous PG synthesis or on the rate of catabolism of prostanoids.

Uterine contractility during pregnancy and the effect of abortifacient drugs

There are a number of compounds in clinical use for termination of pregnancy. Treatment with all of them will result in increased uterine contractility. PGF2 alpha and PGE2 as well as different prostaglandin analogues all have a direct stimulatory effect on the myometrium, while other compounds such as hypertonic saline and Rivanol seem to act mainly through a stimulation of the endogenous production of PGF2 alpha. Treatment with antiprogestins which compete with progesterone at the receptor level or which inhibit progesterone biosynthesis results in an increased uterine contractility probably through a release from progesterone inhibition. If the withdrawal of progesterone also induces an increased endogenous prostaglandin production is unclear. The medical method to induce abortion which best resembles the physiological events during a spontaneous abortion is probably treatment with antiprogestins (receptor blockers or progesterone biosynthesis inhibitors) followed by prostaglandin.

The physiology of cervical ripening and cervical dilatation and the effect of abortifacient drugs

The mechanical properties of the human uterine cervix are determined mainly by the connective tissue component, whereas it is doubtful whether the scanty smooth muscle component is of any physiological importance. Histological and biochemical analyses reveal a fibrous connective tissue similar to that found in skin and tendon. Degradation of the collagen and an increase in some special dermatan sulphate proteoglycans can at least partly explain the pregnancy-associated softening of this connective tissue. Relatively high oestrogen levels seem to be an absolute condition for the process, even when it is induced pharmacologically. Treatment with progesterone-receptor blockers, PGE2, PGF2 alpha or relaxin in pregnancy induce cervical softening as well as histological and biochemical changes which cannot be distinguished from the physiological cervical softening which takes place in late pregnancy. Prostaglandins and relaxin might interact and could include cytokines such as interleukin-1 during the process. The effect of cervical tents cannot be explained only by the radial pressures they exert. Most probably stimulation of local prostaglandin synthesis is also involved.

The physiological and clinical effects of progesterone inhibition with mifepristone (RU 486) in the second trimester

A double-blind placebo-controlled trial was performed in 20 primigravidae to assess the physiological and clinical effects of oral mifepristone on myometrial contractility and sensitivity in the second trimester. Ten women received 600 mg of oral mifepristone and 10 women a placebo 24 h before abortion was induced in both groups, with extra-amniotic PGE2 instillation. Intrauterine pressure recordings demonstrated increased spontaneous uterine activity and increased sensitivity to PGE2 and ergometrine, but no change in oxytocin sensitivity after mifepristone treatment. There were no significant differences in PGE or PGF metabolite concentrations in peripheral maternal plasma over the 24-h study period after treatment between the mifepristone and placebo groups. The mean induction abortion interval in the mifepristone group was 512 (SD 321) min compared with 1128 (SD 606) min in the placebo group (P less than or equal to 0.02). The mechanism whereby mifepristone provokes enhanced uterine contractility and sensitivity to prostaglandins, with a reduction in abortion times, does not appear to be through endogenous production of PGE or PGF.

The interaction between Helicobacter pylori culture filtrate and indomethacin: effects on the integrity of human gastric antral mucosa and its prostaglandin E2 production in vitro

Histopathological methods and radioimmunoassay were used to assess the microstructure and prostaglandin E2 production by paired specimens of human gastric antral mucosa; the specimens were studied after 48 h of incubation in base-line tissue culture medium, Helicobacter pylori culture filtrate, H. pylori culture control fluid, indomethacin, and H. pylori culture filtrate plus indomethacin. When applied alone, the filtrate did not affect the structure of the mucosal tissue or its prostaglandin E2 synthesis. In the overall group (n = 21), specimens incubated with the mixture of H. pylori filtrate and indomethacin had a median histological grade of 1 and prostaglandin E2 of 29 pg/mg tissue, compared to 2 pg/mg (P = 0.04) and 60 pg/mg (P = 0.0007) respectively, in specimens incubated with indomethacin alone. These results indicate that an interaction may exist between indomethacin and a factor contained in H. pylori culture filtrate. Such interaction is damaging to the human gastric antral mucosa, and its understanding might have therapeutic implications.

Effect on gastric and duodenal mucosal prostaglandins of repeated intake of therapeutic doses of naproxen and etodolac in rheumatoid arthritis

The synthesis of gastric and duodenal mucosal prostaglandin E2, prostaglandin I2, and thromboxane B2 during a 60 minute incubation of biopsy specimens, the degree of endoscopic and histological damage, and the anti-inflammatory response were all studied after a four week, double blind study of therapeutic doses of two non-steroidal anti-inflammatory drugs, naproxen and etodolac, received by 27 patients with active rheumatoid arthritis (13 receiving naproxen, 14 etodolac). Prostaglandin values after treatment did not differ from the baseline levels when all the patients were analysed as one group. Subgroup analysis showed that naproxen suppressed gastric prostaglandin E2 from a median of 29 to 9 ng/mg protein, duodenal prostaglandin E2 from 34 to 11 ng/mg, and duodenal prostaglandin I2 from 62 to 15 ng/mg protein. No overall suppression occurred with etodolac. Also, on the second assessment patients receiving naproxen had lower gastric and duodenal prostaglandin E2 and prostaglandin I2, but higher values of duodenal thromboxane B2, than patients receiving etodolac. Both drugs had comparable anti-arthritic activity and caused microscopic gastritis in similar proportions of patients. No correlation was detected between prostaglandin values and the mucosal damage which developed in seven patients receiving naproxen (54%) and three receiving etodolac (21%). These findings indicate that, unlike naproxen, etodolac does not seem to affect gastric or duodenal prostaglandin synthesis; other mechanisms of injury need to be considered.

Antiprogesterone RU 486--a drug for non-surgical abortion

RU 486 is the first steroidal antiprogesterone in clinical use. It acts by binding to progesterone receptor, thus blocking the effects of progesterone at the uterine level, and provoking endometrial necrosis and shedding. RU 486 can, therefore, be used to interrupt early human pregnancy. In pregnancies of up to 7-8 weeks duration, the rate of complete abortions with RU 486 has ranged from 50% to 90%. The success rate can, however, be augmented up to 95%-100% by combining RU 486 with a low dose prostaglandin. RU 486 induced abortion has been well tolerated by women and highly acceptable to them. The bleeding starts 2-3 days after RU 486 administration lasting for 12-14 days. Possible clinical uses of RU 486 include induction of menstruation, late post-coital contraception, induction of labour after intrauterine fetal death, preoperative cervical ripening and treatment of progesterone receptor positive mammary tumours. When administered in the follicular phase of the cycle, RU 486 inhibits follicular development. In addition, the antiglucocorticoid properties of RU 486 have been used in symptomatic treatment of hypercortisolemia of Cushings disease. The pharmacokinetics of RU 486 are characterised by high micromolar serum concentrations, long half-life of 26-48 hours and substantial metabolism after oral administration. Although effective and well tolerated, RU 486 has aroused great moral controversy, which is currently hampering further testing and distribution of the drug. So far RU 486 has been accepted for termination of pregnancy in France and in the Peoples Republic of China, to be used with prostaglandins and under strict medical surveillance.

Induced cervical ripening with mifepristone (RU 486) and bioconversion of arachidonic acid in human pregnant uterine cervix in the first trimester. A double-blind, randomized, biomechanical and biochemical study

The effect of mifepristone on the uterine cervix was studied in 55 nulliparae at 7 to 10 weeks gestation, wishing to undergo a vacuum aspiration. The patients were randomly assigned to three groups which received preoperative drug or placebo treatment starting 36 or 48 hours before surgery. Cervical biopsies from 12 of the subjects were used in a double-blind test to study the bioconversion of 14C-labeled arachidonic acid. By using an objective method to study the cervical resistance to dilatation, it was shown that the cervix was significantly less (p less than 0.05) resistant to dilatation after pretreatment with mifepristone compared to placebo. The longer treatment was significantly (p less than 0.05) more effective than the shorter. No significant difference of the 14C-arachidonic acid bioconversion was demonstrated.

The antiprogesterone steroid, RU 486 (mifepristone)

RU 486 (Mifepristone) represents a major development in the field of hormone antagonists as the first effective antiprogestogen. A number of therapeutic roles for the drug are envisaged. It is already being used extensively around the world for the procurement of first trimester abortion--particularly in combination with prostaglandins. It also has been shown to be effective as a cervical ripening agent and for the induction of labour. Initial human studies have involved nonviable pregnancies and more work is needed in animal models before the drug can be deemed safe for use in viable human pregnancies in the third trimester.

Interaction of RU 486, a glucocorticoid and progestin antagonist with human circulating mononuclear leukocytes

The glucocorticoid and progestin antagonist, RU 486 (17 beta-hydroxy-11 beta-[4-dimethylaminophenyl]-17 alpha-[1-propynyl]-estra-4, 9-dien-3-one), antagonizes the suppressive effect of dexamethasone on [14C]2-deoxyglucose uptake by intact human mononuclear leukocytes in a concentration-dependent fashion. The authors found at least two types of specific-binding sites for this compound in the mononuclear leukocytes. The first type of sites (receptor content [Ro], 10.8 +/- 1.6 fmoles/10(6) cells [mean +/- SD of 4 experiments]; equilibrium dissociation constant (Kd), 0.3 +/- 0.1 nM) have a capacity similar to that of the dexamethasone binding site (Ro, 11.2 fmoles/10(6) cells; Kd, 1.2 nM). The second type of sites (Ro, 56 +/- 27 fmoles/10(6) cells: Kd, 19 +/- 5 nM) have a higher capacity and lower affinity for RU 486 than the first type of sites and do not interact with dexamethasone. The authors were unable to demonstrate the presence of the second type of binding sites in subcellular fractions. This finding suggests that this site is unstable and lost in the fractionation process. The role of the second type of low-affinity, high-capacity RU 486 specific-binding site in intact human mononuclear leukocytes, as well as its possible occurrence in other tissue, requires further investigation.

The effects of progesterone receptor blockade in the luteal phase of normal fertile women

The effects of a single, variable dose (5 to 200 mg) of RU38486 (RU486) (Roussel-Uclaf, Paris, France) in the first half of the luteal phase of the menstrual cycle were studied in 30 normal fertile volunteers. Quantitative histologic techniques were employed, and the results were compared with normal ranges derived from a separate, normal, fertile population. It was found that RU486 inhibited glandular secretory activity, accelerated degenerative changes, induced various vascular changes, increased stromal but not glandular mitotic activity, and did not affect the predecidual reaction. The superiority of morphometric analysis over traditional dating criteria was demonstrated in this study of endometrial responses to an exogenously administered agent. In addition, it was found that temperature drop occurred in 56%, menstrual induction in 43%, luteolysis in 24%, mood change in 23%, and thirst sensation in 3% of women studied. Both menstrual induction and changes in hypothalamic function after the administration of RU486 occurred independently of luteolysis and so were likely to be the direct result of progesterone receptor blockade in these organs. Menstrual induction was significantly related to the dose given and the day on which RU486 was administered. Mood change was significantly related to the day on which RU486 was given. Most of the effects of RU486 occurred around 48 hours after its administration.

Anti-progesterones: background and clinical physiology

The development of anti-progesterones has provided a probe to examine the role of progesterone both in the normal cycle and in pregnancy. The most widely used of these agents, mifepristone, appears to act both directly at the endometrial progesterone receptor, and centrally by reducing circulating gonadotrophin concentrations. In addition, ovarian steroidogenesis may be modified. The clinical application of these agents for the interruption of pregnancy will be considered in the following chapters.