The effect of the antiprogestins RU 486 and ZK 98734 on the synthesis and metabolism of prostaglandins F2 alpha and E2 in separated cells from early human decidua

Enriched preparations of glandular and stromal cells were obtained from early human decidua and incubated for 24 h in the presence of two progesterone antagonists, RU 486 (17 beta-hydroxy-11 beta-[4-dimethylaminophenyl]17 alpha-[1-propynyl]-estra-4,9-dien-3-one) and ZK 98734 (17 beta-hydroxy-11 beta-4[4-dimethylaminophenyl]17 alpha-[3-hydroxy-1-propynyl]estra-4,9-dien-3-one) to determine the effect of the antiprogestins on the release of prostaglandin F2 alpha (PGF2 alpha) and PGE2 and their subsequent conversion to 15-keto-13,14-dihydro-PGF2 alpha and 15-keto-13,14-dihydro-PGE2. In the presence of exogenous arachidonic acid (AA, 30 microM), both steroids stimulated PGF2 alpha release by glandular, but not stromal, cells (P less than 0.001) and inhibited the metabolism of PGF2 alpha by the glandular fraction (P less than 0.005 and P less than 0.001 respectively). In the absence of exogenous AA, RU 486 and ZK 98734 stimulated the release of PGF2 alpha from glandular, but not stromal, cells (P less than 0.001 and P less than 0.005, respectively). Neither steroid altered the release or metabolism of PGE2 when the cells were incubated with AA, but both RU 486 and ZK 98734 increased the release of PGE2 by glandular, but not stromal, cells when incubated without AA (P less than 0.005 and P less than 0.001, respectively). Both steroids inhibited the metabolism of PGE2 under these conditions (P less than 0.05). These results suggest that 1) antiprogestins stimulate the synthesis of PGs by glandular cells in early human decidua, but do not alter the synthesis of PGs by stromal cells; 2) this stimulation of PG synthesis involves an effect on cyclooxygenase activity and is not a consequence of increased availability of endogenous AA; 3) the metabolism of PGs by glandular cells is altered by RU 486 and ZK 98734; 4) as RU 486 has greater antiglucocorticoid activity than ZK 98734, these results suggest that both steroids act on decidua by antagonizing endogenous progesterone rather than glucocorticoid activity.     

RU 486 inhibits peripheral effects of glucocorticoids in humans

RU 486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one] is a synthetic steroid receptor antagonist. To evaluate the peripheral antiglucocorticoid action of this compound, we investigated its ability to antagonize cutaneous steroid-induced vasoconstriction. This phenomenon, produced by three different topical steroids in six normal men, was consistently and significantly attenuated or abolished by oral administration of 6 mg/kg RU 486. This demonstration of a peripheral action of RU 486 is important in relation to the potential therapeutic use of this well tolerated drug in states of hypercortisolism. It also indicates that the cutaneous vasoconstrictor effects of topical steroids are mediated by occupancy of glucocorticoid receptors.     

Inhibition of growth by the antihormone RU486 in different hepatoma cell lines.

The synthetic steroid RU486 (17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)-17 alpha-(1-propynyl)-estra-4,9-dien-3-one), which has been shown to display antiprogestin and antiglucocorticoid properties in different systems, exerts antiglucocorticoid effects and inhibits the cell growth in a concentration-dependent manner on Reuber rat hepatoma cell variants. This effect can be observed on glucocorticoid-sensitive cells, containing glucocorticoid receptors, and on glucocorticoid-resistant cells displaying a very low level of dexamethasone binding. Metabolization of RU486 occurs in different glucocorticoid-resistant hepatoma variants; these cells are less sensitive to the growth inhibitory effect of the antihormone than the steroid-sensitive cells which do not metabolize RU486. Thus, metabolization of RU486 must also be taken into account for the efficacy of this antagonist on cell growth.     

The antiprogestin RU38 486: receptor-mediated progestin versus antiprogestin actions screened in estrogen-insensitive T47Dco human breast cancer cells

Despite the theoretical promise of synthetic antiprogestational agents as anticancer agents, experimental tools, midcycle contraceptives, and implantation inhibitors, none has been available for either basic or clinical studies. However, a candidate antiprogestin, RU38 486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(1-propynl)estra-4,9 -dien-3-one], has recently been described that has antiprogestational and antiglucocorticoid activities in early clinical trials. Its mechanisms of action are unclear. Furthermore, development of this drug underscores an old bioassay problem: that biological screening of progestins and antiprogestins is complex because of the physiological requirement that progestational effects must be superimposed upon an estrogenized system. This has made it difficult to distinguish among progestational, antiprogestational, and antiestrogenic properties of unknown agents. Here we describe the use of T47Dco human breast cancer cells to circumvent these problems. T47Dco cells are rich in progesterone receptors (PR), but are resistant to estrogens and antiestrogens. Their PR are estrogen-independent, and this permits progestins to be studied in an estrogen-free system. We have used these cells to assess the receptor-binding properties and the biological actions of RU38 486. Since RU38 486 absorbs UV at approximately 300 nm, this wavelength was used to covalently photolink the drug to PR in situ. Like the synthetic progestin R5020, low concentrations (10 nM) of [3H]RU38 486 bind two PR subunits in nuclei of T47Dco; glucocorticoid receptors are not bound. RU38 486 has a high affinity for PR in vitro (Kd approximately 2 nM at 0-4 C), and in intact cells, low concentrations (6-8 nM) transform more than 95% of PR to a high affinity nuclear binding state. In contrast to progesterone, the compound is not metabolized, so that it chronically (3-6 days) suppresses PR replenishment. These biochemical properties of RU38 486 are typical of synthetic progestins, but distinguish it from pure glucocorticoids. To bioassay RU38 486, we have measured growth and insulin receptors, since in T47Dco, physiological concentrations of progestins inhibit proliferation and increase the number of cell surface insulin-binding sites. Like progestins, RU38 486 is growth inhibitory; unlike progestins, it fails to stimulate insulin receptors and partially blocks their stimulation by R5020. Thus, RU38 486 has dual progestin agonist/antagonist actions depending on the biological response measured.     

Pituitary-adrenal response to the antiglucocorticoid action of RU 486 in Cushing's syndrome

RU 486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one] is a steroid analog which antagonizes glucocorticoid action at the receptor level. The pituitary-adrenal response to RU 486 was evaluated in patients with Cushing's syndrome. The acute administration of 400 mg RU 486 at 0800 h in five patients with Cushing's disease induced no significant change in plasma cortisol during the next 10 h compared with the administration of placebo. However, prolonged administration (400 mg daily for 3 days) caused activation of the pituitary-adrenal axis; urinary cortisol increased the most from 727 to 5720, 830 to 8200, 610 to 1020, 110 to 570, and 300 to 990 micrograms/day. Plasma cortisol and lipotropins increased to a lesser extent. Hormone changes appeared on the second day of drug administration and lasted up to 3-4 days after the drug was discontinued. In two patients with nonpituitary-dependent Cushing's syndrome, RU 486 induced no significant change in steroid secretion. We conclude that RU 486 induced a delayed and prolonged pituitary-adrenal response in Cushing's disease; whether the resulting cortisol overproduction will overcome the peripheral effect of RU 486 remains to be determined.     

Effects of an antiprogesterone (RU486) on the hypothalamic-hypophyseal-ovarian-endometrial axis during the luteal phase of the menstrual cycle

The impact of the antiprogesterone RU486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl) 17 alpha-(1-propynyl)estra- 4,9-dien-3-one] on the hypothalamic-pituitary-ovarian-endometrial axis was examined in normal cycling women during the mid (MLP)- and late (LLP) luteal phases. During the MLP, 10 women received 3 mg/kg RU486 for 3 days. During the LLP, a single dose of 600 mg RU486 was administered to 4 women, and in another 4 women a single dose of 3 mg/kg was given during corpus luteum rescue by hCG. Longitudinal studies with daily and frequent blood samples (every 10 min for 10 h) were conducted during 3 consecutive cycles (control-treatment-recovery). During the MLP, RU486-induced uterine bleeding occurred in all 10 women 36-72 h after the first dose. No histological evidence of endometrial breakdown was found in endometrial biopsies taken 12-24 h before the onset of bleeding. Significant decreases in LH secretion (P less than 0.001) and LH pulse amplitude (P less than 0.006) and blunted pituitary responses to GnRH (P less than 0.01) were evident by the last treatment day, but LH pulse frequency did not change. Complete luteolysis occurred in 2 of the 10 women. Incomplete luteolysis occurred in 8 women and was associated with an initial decline of serum estradiol (P less than 0.001), but not progesterone levels, followed by rebound increases (P less than 0.001) in LH, estradiol, and progesterone levels 3 days later, which may have reversed the luteolytic processes and prolonged corpus luteum function. Spontaneous luteolysis ensued 3-5 days later with the onset of second episodes of uterine bleeding. For serum FSH, an early rise occurred during the luteal phase in advance of the onset of the second episodes of uterine bleeding. This rise may have resulted in early follicle recruitment and accounted for the shorter duration of the follicular phase during recovery cycles. During the LLP, the single RU486 dose resulted in significant decreases in LH pulse amplitude (P less than 0.03), frequency (P less than 0.05), and secretion (not significant) within 12 h. The recovery cycle was entirely normal. Corpus luteum rescue with incremental doses of hCG did not prevent uterine bleeding after RU486 treatment. These findings indicate that RU486 operates at multiple sites and implies that progesterone is important in the control of luteal function. Further, our data provide a basis for exploring the potential use of RU486 as a once a month birth control agent.     

Effects of the antiprogesterone steroid RU 486 during midluteal phase in normal women

The antiprogesterone steroid RU 486 (17 beta-hydroxy-11 beta-4-dimethyl-aminophenyl)17 alpha(1-propynyl)estra-4,9-dien-3-one) was given orally to 32 normally cycling women for 4 days, starting on the fourth day of the luteal phase. Uterine bleeding occurred on the third day of RU 486 administration in all 14 women treated with 100 mg/day, in 7 of the 8 women treated with 50 mg, and in 8 of 10 women receiving 25 mg/day. Premature luteal regression induced by RU 486 occurred in 8 women treated with 100 mg/day, in 3 treated with 50 mg, and in 2 receiving 25 mg/day. Plasma LH was measured every 15 min from 0800-1200 h for 5 days in 17 women. Mean LH levels decreased and pulsatile release disappeared in 7 of the 8 women treated with 100 mg, in 2 of 4 receiving 50 mg, and in 1 of 5 treated with 25 mg. RU 486 had no effect when given to 5 women with anovulatory cycles for 4 days starting on day 18 of the cycle. In conclusion: 1) RU 486, given to normally cycling women at midluteal phase, provokes uterine bleeding. 2) This effect occurs whether or not luteal regression is induced by the compound, indicating that RU 486 acts directly upon the endometrial tissue, very likely at the progesterone receptor level. 3) The drug may impair simultaneously or separately luteal function and gonadotropin secretion in a dose-dependent manner. 4) The lack of antiglucocorticosteroid activity, at the dosage of 100 mg/day, suggests that RU 486 may be useful for fertility control.     

Glucocorticoid receptor-mediated induction of glutamine synthetase in skeletal muscle cells in vitro

We studied the regulation by glucocorticoids of glutamine synthetase in L6 muscle cells in culture. Glutamine synthetase activity was strikingly enhanced by dexamethasone. The dexamethasone-mediated induction of glutamine synthetase activity was blocked by RU38486 [11 beta-(4-dimethylaminophenyl)17 beta-hydroxy-17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one], a glucocorticoid antagonist, indicating the involvement of intracellular glucocorticoid receptors in the induction process. RU38486 alone was without effect. Northern blot analysis revealed that dexamethasone-mediated enhancement of glutamine synthetase activity involves increased levels of glutamine synthetase mRNA. Increased enzyme activity was specific for glucocorticoids; other steroid hormones were essentially without effect. The induction of glutamine synthetase was selective, in that glutaminase activity was not induced by dexamethasone treatment of L6 cells. Thus, glucocorticoids regulate the expression of glutamine synthetase mRNA in cultured muscle cells via interaction with intracellular receptors. Such regulation may be relevant to control of glutamine production by muscle.     

Blockade of glucocorticoid receptor binding and inhibition of dexamethasone-induced muscle atrophy in the rat by RU38486, a potent glucocorticoid antagonist

Glucocorticoid hormones cause marked muscular atrophy, the mechanism of which is unknown. We employed a potent glucocorticoid antagonist, RU38486 [11 beta-(4-dimethylaminophenyl)17 beta-hydroxy-17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one], to determine whether intracellular glucocorticoid receptors are involved. RU38486 was shown to be an effective blocker of glucocorticoid receptor binding in vivo and in vitro. Furthermore, this compound significantly blocked the loss of body and muscle weight caused by injection of dexamethasone. These data indicate that intracellular glucocorticoid receptors are important in the etiology of steroid myopathy. Studies with glucocorticoid antagonists may lead to the design of specific therapeutic modalities for the treatment of both endogenously and exogenously produced steroid myopathies.     

The effects of RU 486 on immune function and steroid-induced immunosuppression in vitro

The effect of RU 486 [17 beta-hydroxy-11 beta-(4-dimethylamino-phenol)17 alpha-(prop-1-ynyl)estra- 4,9diene-3-one] on [3H]thymidine incorporation into Concanavalin-A-stimulated human peripheral blood mononuclear cells and its influence on the suppressive effects of cortisol and progesterone were investigated. Cortisol suppressed lymphocyte thymidine incorporation at 10(-5), 10(-6), and 10(-7) M (17.6%, 20%, and 38% of control, respectively; P less than 0.01). Cortisol-induced suppression was reversed when low concentrations of RU 486 (10(-7) and 10(-6) M) were added. RU 486 at 10(-5) M further suppressed lymphocyte thymidine incorporation when added to cultures with cortisol. Progesterone significantly inhibited lymphocyte thymidine incorporation at 10(-5) M (8.2% of control; P less than 0.01). No reversal of progesterone-induced suppression of thymidine incorporation was seen when RU 486 was added to cultures; rather, further suppression of thymidine incorporation was seen. RU 486 alone in culture at concentrations achieved therapeutically (10(-5) M) significantly inhibited thymidine incorporation (7.2% of control; P less than 0.01). These findings suggest that RU 486 may have dose-dependent mixed agonist/antagonist effects on cortisol-induced immunosuppression. The lack of an antagonist effect of RU 486 on progesterone suggests that progesterone's immunosuppressive effects may not be receptor mediated. Finally, our findings would suggest that some immunosuppression may be seen at currently used doses of RU 486.     

Late luteal phase administration of RU486 for three successive cycles does not disrupt bleeding patterns or ovulation

RU486, a 19-nor steroid, binds with high affinity to the receptors for progesterone and glucocorticoids, blocking the actions of these hormones on their target tissues. We conducted studies to determine whether RU486 administered at the end of the luteal phase would disturb the menstrual rhythm, ovulation, or hormonal parameters in the treatment and post-treatment cycles. The first study was done in six surgically sterilized women during two consecutive cycles. RU486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(1-propynyl)estra-4,9-dien-3-one; 100 mg/day] was given for 4 consecutive days, commencing on days 23-27 of the first cycle. Menstrual bleeding occurred by the second day of RU486 administration in all women and was indistinguishable from their usual bleeding pattern. The onset of this bleeding was advanced by RU486 administration, since it entailed shortening of the luteal phase with prolongation of the following follicular phase. Serum LH, FSH, estradiol, and progesterone levels were normal in five of the six women in both the treatment and posttreatment cycles. The second study was conducted in 10 women who were not exposed to the risk of pregnancy. RU486 (100 mg/day) was given for 4 consecutive days, commencing 4 days before their expected menses for 3 successive cycles, preceded and followed by 2 placebo-treated cycles. Bleeding patterns were indistinguishable during the RU486 and placebo cycles. Late luteal phase administration of RU486 consistently produced menstrual bleeding within 1-3 days of drug administration. Daily early morning urinary LH excretion in 6 women and estrone glucuronide and pregnanediol glucuronide excretion in 5 women during both placebo and RU486 cycles were consistent with luteinization, suggesting ovulation and appropriate corpus luteum function. We conclude that RU486 has no major effect on menstrual cycle events if given at the time of the natural progesterone withdrawal that occurs before menses in nonpregnant women.     

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.     

Blockade of the spontaneous midcycle gonadotropin surge in monkeys by RU 486: a progesterone antagonist or agonist?

Preovulatory ovarian secretion of progesterone (P4), several hours before the onset of the typical midcycle gonadotropin surge, occurs in humans and monkeys. We investigated the potentially obligatory role of preovulatory P4 secretion in stimulating the midcycle LH surge by administering a potent P4 antagonist, RU 486(17 beta-hydroxy-11 beta-[4-dimethylaminophenyl-1]17 alpha-[prop-1-ynyl]estra-4,9-dien-3-one), to sexually mature, normally ovulatory cynomolgus monkeys on days 10-12 of the menstrual cycle (n = 18). Monkeys were randomized to receive RU 486 alone (5 mg/day, im; group I); RU 486 plus dexamethasone (1 mg/day, im; group II); dexamethasone alone (group III); or vehicle (ethanol; 0.5 ml; group IV). Before drug treatment, the follicular phases were quite similar among groups. The administration of RU 486 blocked (delayed) the expected gonadotropin surge, despite rising estrogen concentrations (greater than 250 pg/ml). The expected LH surge was delayed by RU 486 (n = 5) or RU 486 with dexamethasone (n = 3) until 36 +/- 7 (+/- SEM) and 27 +/- 8 days in groups I and II, respectively. In contrast, groups III (n = 3) and IV (n = 5) had timely midcycle surges after the administration of dexamethasone or vehicle alone (4 +/- 2 and 6 +/- 2 days, respectively). The intermenstrual interval was lengthened by RU 486 administration in both group I and II animals (61 +/- 6 and 54 +/- 6 days) compared to controls (30 +/- 2; P less than 0.0001). In summary, RU 486 effectively blocked imminent midcycle gonadotropin surges, delayed subsequent folliculogenesis, and significantly extended the menstrual cycle length. If RU 486 acted as a pure P4 antagonist, then P4 is necessary for timely midcycle gonadotropin surges to occur. However, recent evidence showing agonistic properties of RU 486 (in the virtual absence of P4) at both endometrial and pituitary levels may favor a P4-like (agonistic) blockade of the estrogen-induced FSH/LH surges by RU 486.     

Antagonism of female sexual behavior with intracerebral implants of antiprogestin RU 38486: correlation with binding to neural progestin receptors

The steroidal antiprogestin 17 beta-hydroxyl-11 beta-(4-dimethylaminophenyl)-17 alpha-(1-propynl)estra-4,9-dien-3-one (RU 38486) was administered systemically or was implanted into the ventromedial hypothalamus and other brain regions (habenula, preoptic area, interpeduncular region, in order to determine whether the compound could antagonize progesterone (P) activation of estrous responsiveness and whether the compound would exert its behavioral effects at the presumed site of P action and/or at other neural sites implicated in the regulation of female sexual behavior. RU 38486 (5 mg) administered sc 1 h before 200 micrograms P inhibited P facilitation of lordosis behavior in estrogen-primed rats. Intracerebral application of RU 38486 to the ventromedial hypothalamus reduced lordosis responses in 14 of the 25 animals tested. Similar implants in the habenula also inhibited lordosis in 5 of the 14 animals tested. Antiprogestin implants in the interpeduncular region and preoptic area were virtually without effect (1 of 7 inhibited in each group). Interactions of RU 38486 with steroid binding sites in the hypothalamus-preoptic area (HPOA) were also assessed. RU 38486 appeared to be a competitive inhibitor of progestin ([3H] R5020) binding in HPOA cytosols. Scatchard analysis of [3H]RU 38486 binding showed that when unlabeled P was used as the competitor to assess nonspecific binding, the antiprogestin bound with high affinity [dissociation constant Kd = 8.4 nm] to brain cytosols. In addition, the number of [3H]RU 38486 binding sites in HPOA cytosol increased by approximately 50% in estrogen-primed female rats. Competition studies indicated that unlabeled RU 38486 was the most effective competitor for [3H]RU 38486 binding but that P and R5020 were nearly as effective. Corticosterone, hydrocortisone, deoxycorticosterone, and triamcinolone also competed for [3H]RU 38486 binding but were somewhat less effective than the progestins. Testosterone and estradiol did not displace [3H]RU 38486 except at very high molar excesses. Thus RU 38486 appears to bind with highest affinity to HPOA progestin receptors, but it also binds to glucocorticoid receptors. These data are consistent with the interpretation that inhibition of estrous responsiveness by RU 38486 is associated with the antagonist's interference with brain progestin binding.     

Successful treatment of Cushing's syndrome with the glucocorticoid antagonist RU 486

A patient with Cushing's syndrome due to ectopic ACTH secretion was treated successfully with the new glucocorticoid antagonist RU 486 [17 beta-hydroxy-11 beta-(4-dimethylamino phenyl) 17 alpha-(1-propynyl)estra-4,9-dien-3-one]. This compound is a 19-nor steroid with substitutions at positions C11 and C17 which antagonizes cortisol action competitively at the receptor level. Oral RU 486 was given in increasing doses of 5, 10, 15, and 20 mg/kg . day for a 9-week period. Treatment efficacy was monitored by assessment of clinical status and by measuring several glucocorticoid-sensitive variables, including fasting blood sugar, blood sugar 120 min after oral glucose administration, and plasma concentrations of TSH, corticosteroid-binding globulin, LH, testosterone-estradiol-binding globulin, and total and free testosterone. With therapy, the somatic features of Cushing's syndrome (buffalo hump, central obesity, and moon facies) ameliorated, mean arterial blood pressure normalized, suicidal depression resolved, and libido returned. All biochemical glucocorticoid-sensitive parameters normalized. No side-effects of drug toxicity were observed. We conclude that RU 486 may provide a safe, well tolerated, and effective medical treatment for hypercortisolism.     

Attenuation of preovulatory gonadotrophin surges by epostane: a new inhibitor of 3 beta-hydroxysteroid dehydrogenase

Epostane, an inhibitor of 3 beta-hydroxysteroid dehydrogenase, was administered orally to pro-oestrous rats to evaluate further a possible role for preovulatory progesterone secretion in eliciting surges of LH and FSH. Whereas a dose of 10 mg epostane/kg had essentially no effects on preovulatory gonadotrophin surges and ovulation, 200 mg epostane/kg markedly attenuated LH and FSH surges and blocked ovulation. A dose of 50 mg epostane/kg exerted effects on LH and FSH surges and ovulation intermediate between those of doses of 10 and 200 mg/kg. Plasma concentrations of progesterone were significantly lower in all anovulatory epostane-treated rats at 18.00 and 22.00 h on proestrus than those measured in vehicle-treated rats. Concurrent injection of 2 mg progesterone in rats given 200 mg epostane/kg restored gonadotrophin surges to normal, but consistently failed to reverse the inhibitory effects of epostane on ovulation. Peak plasma progesterone levels produced by the progesterone injections were eight- to tenfold higher than the highest levels measured in vehicle-treated rats during the afternoon of pro-oestrus. Insertion of progesterone capsules was less effective than injections of progesterone in restoring gonadotrophin surges to normal, even though peak plasma progesterone concentrations achieved after insertion of two 20 mm long progesterone capsules were double the peak progesterone concentrations measured in control rats. Nevertheless, taken together with recent reports showing attenuation of preovulatory gonadotrophin surges by the progesterone antagonist RU 486 (17 beta-hydroxy-11 beta-[4-dimethyl-aminophenyl]-17 alpha-[prop-1-ynl] estra-4,9-diene-3-one), the present results provide support for a role of preovulatory progesterone secretion in enhancing oestrogen-dependent LH/FSH surges on pro-oestrus.     

Progesterone action in normal mouse mammary gland

Previously it has been shown that progesterone, as well as estrogen, plays an important role in the growth of the mammary gland. Eighty percent of mammary progesterone receptors (PgR) are estrogen-inducible and are localized in the epithelium; the remaining 20% of PgR are estrogen-independent and appear to be localized in the mammary stroma. The purpose of the present study was to investigate how progestins promote mammary growth in relation to their interactions with epithelial and stromal components of the gland and to assess the role of estrogen in these interactions. Progestins [progesterone, [17 beta-methyl-3H]promogestone (R5020), and medroxy progesterone acetate] alone or in combination with estrogen were combined with Elvax 40P and implanted directly into mammary glands. The effect of hormones on cell proliferation was determined by observing changes in mammary gland morphology and by quantitating DNA synthesis in both epithelial and stromal cells by DNA histoautoradiography. The results demonstrate that in mammary epithelial cells the effects of progestins on mammary gland morphology and DNA synthesis are locally mediated such that proliferative changes in the hormone-implanted glands were greater than in contralateral control glands. Dose-response studies with estrogen and R5020 revealed that the extent of progestin activity was only partially dependent upon the R5020 dose with the major determining factor being the dose of estrogen. Analysis of the effect of estrogen on mammary PgR concentration indicates that the degree and pattern of the morphological response of ductal sidebranching and increases in DNA synthesis are largely due to the increase in estrogen-dependent PgR. The antiprogestin, 11 beta-(4-dimethylamino-phenyl)1-17 beta-hydroxy-17 alpha-(prop-1ynyl)-estra-4,9-diene-3-one (RU486), blocks the proliferation in the epithelium that is mediated through estrogen-dependent PgR. In contrast, in stromal cells progestin activity is not estrogen-dependent, and stimulation of DNA synthesis was not confined to the hormone-implanted glands. Furthermore, RU486 stimulates stromal cell DNA synthesis, and this response is augmented by estrogen. While progestin effects in epithelial cells appear to be mediated by estrogen-dependent PgR, the mechanism operative in stromal cells appears to be different and remains to be elucidated.     

The new steroid analog RU 486 inhibits glucocorticoid action in man

RU 486 [17 beta-hydroxy-11 beta-(4- dimethylaminophenyl )-17 alpha-(prop-1- ynyl )-estra-4,9-dien-3-one] is a new steroid analog which antagonizes glucocorticoid action at the receptor level in animals. To assess its potential antiglucocorticoid activity in man we studied the pituitary-adrenal response to RU 486 in normal men. The compound was administered at 0200 h and plasma cortisol and lipotropins (LPH) were measured hourly for 10 h. After 400 mg RU 486 significant and sustained elevation of both hormones occurred during the 0700-1200 h period: mean (+/- SE) plasma levels after placebo or RU 486 during this interval were, respectively, for cortisol (ng/ml), 63.4 +/- 8.2 and 112.7 +/- 2.9 (P less than 0.02); and for LPH (pg/ml), 34.8 +/- 11.3 and 71.6 +/- 15.4 (P less than 0.01). The 200- and 100-mg doses induced only transient cortisol and LPH increases. Administration of RU 486 (400 mg) at 1400 h induced no increase in plasma cortisol compared to placebo in the corresponding 2000 to 2400 h period. When RU 486 was administered concomitantly with dexamethasone (1 mg) at 2400 h, dose-dependent blockade of the dexamethasone-induced cortisol suppression at 0900 h was found (r = 0.62, P less than 0.01); this blockade was partial after the 100-mg dose, but complete after the 400-mg dose. Plasma LPH and ACTH showed parallel variations. We conclude that RU 486 antagonizes the negative pituitary feedback of both the nocturnal endogenous cortisol rise and exogenously administered dexamethasone. These actions are consistent with an antiglucocorticoid activity of this compound in man.     

Induction of LH hypersecretion in cyclic rats during the afternoon of oestrus by oestrogen in conjunction with progesterone antagonism or opioidergic blockade

The pro-oestrous secretion of progesterone that follows the LH surge in the rat limits the expression of the daily signal for LH surge initiation until the following oestrous cycle. This study explored the role of endogenous opioid peptides in the extinction by progesterone of the signal for the LH surge induced by oestrogen. Intact cyclic rats underwent external jugular venous cannulation on dioestrus, and were allowed to elicit a spontaneous pro-oestrous LH surge. On the afternoon of pro-oestrus, rats received an s.c. injection of oestradiol and an s.c. injection of either oil, 17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(prop-1-ynyl)oestra-4,9,dien-3-one (RU 486; a synthetic anti-progestin), or N-cyclopropylmethyl-6-desoxy-6-methylene-noroxy-morphone (nalmefene; a long-acting opiate antagonist). Repeat doses of each were administered on the morning of oestrus to maintain increased oestrogen levels, and either progesterone or opioidergic blockade. Plasma was obtained from 13.00 to 19.00 h on oestrus for determination of the concentration of rat LH. Rats treated with oestradiol alone demonstrated consistently low concentrations of LH throughout the afternoon of oestrus. Rats treated with both oestradiol and either RU 486 or nalmefene demonstrated spontaneous augmentations of rat LH concentration during the afternoon of oestrus, which, although of diminished amplitude as compared with that seen in pro-oestrus, were consistent with a reactivation of the LH surge-generating mechanism. Rats treated with nalmefene in the absence of oestradiol were unable to augment LH secretion spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)