NRF2 is overexpressed in ovarian epithelial carcinoma and is regulated by gonadotrophin and sex-steroid hormones.

Aberrant nuclear factor-erythroid 2 (NRF2) expression correlates with tumor development. We investigated NRF2 expression in ovarian epithelial carcinoma (OEC), aiming to identify associations with clinicopathological factors, hormones and induced reactive oxygen species (ROS). Immunohistochemical staining for NRF2 expression was performed on 10 benign cystadenomas, 4 boderline tumors and 64 OECs. Western blotting was used to determine the effects of hormones on NRF2 expression in OEC. NRF2 protein was found to be overexpressed in OEC. Gonadotrophins and estrogen induced ROS production in OEC; these hormones also enhanced NRF2 expression. Therefore, aberrant expression may be induced by hormones through ROS signaling. Increased NRF2 expression may be a molecular event in OEC carcinogenesis.

The regulation of ciliary beat frequency by ovarian steroids in the guinea pig Fallopian tube: interactions between oestradiol and progesterone.

Ciliary beat frequency (CBF) was measured in slice preparations of the Fallopian tube fimbria, using videomicroscopy with a high-speed (500 Hz) camera in guinea pigs that were treated with ß-oestradiol benzoate (ßE2B) and medroxy progesterone (mPRG). In non-ovulating guinea pigs at 4 weeks of age, the CBF of the fimbria was high (17.8 Hz). In sexually mature guinea pigs (12-16 weeks of age) with constant ovulation, the CBF varied from 12 Hz to 16 Hz. The in vivo administration of both ICI-182,780 (a blocker of ßE2 receptors) and mifepristone (a blocker of PRG receptors) induced high CBF (17.4 Hz). The administration of ßE2B at a low (3.2 mg/kg/day) or high (32 mg/kg/day) dose decreased the CBF to 14.5 Hz or 11 Hz, respectively. ICI-182,780 abolished the ßE2B-induced changes in CBF and decreased CBF to 12 Hz. The administration of mPRG (6.4 mg/kg/day) decreased CBF to 12.5 Hz. Mifepristone abolished this mPRG-induced decrease in CBF and maintained the CBF at 15 Hz. However, administering both ßE2B and mPRG increased CBF to 17.5 Hz, suggesting that ßE2B inhibits mPRG actions and vice versa. To confirm the interactions between ßE2B and mPRG, we administered both ßE2B and mPRG to guinea pigs that were pretreated for 1.5 days with either mPRG (6.4 mg/kg/day) or ßE2B (3.2 mg/kg/day). Prior treatment with ßE2B or mPRG prevented the increase in CBF that was otherwise by ßE2B plus mPRG, and maintained the CBF at 14.5 Hz or 13 Hz, respectively. The administration of ßE2B plus mPRG still induced the expression of PRG receptors, indicating that the highest CBF is not the result of no expression of the receptors. In the beating cilia of the fimbria, the signals that are activated by the ßE2 and PRG receptors are proposed to antagonize each other in regulating the frequency.

Overexpressed epidermal growth factor receptor (EGFR)-induced progestin insensitivity in human endometrial carcinoma cells by the EGFR/mitogen-activated protein kinase signaling pathway.

BACKGROUND: Fertility-sparing management is an important treatment for young women who have endometrial carcinoma (EC). Many patients with EC exhibit insensitivity or resistance to progestin therapy, and the molecular mechanisms of that insensitivity and resistance have been elusive. Epidermal growth factor receptor (EGFR) overexpression has been observed in EC, but the roles of EGFR in progestin resistance have not been investigated. METHODS: EGFR and progesterone receptor isotype B (PR-B) messenger RNA and protein levels were determined in EC tissue samples and cell lines by immunohistochemical, real-time reverse transcriptase-polymerase chain reaction and Western blot analyses. The biologic function of EGFR in the regulation of PR-B expression and induced progestin resistance was investigated by transfecting recombinant plasmids that expressed EGFR into Ishikawa EC cells. In addition, the role of the mitogen-activated protein kinase (MAPK) signal pathway was investigated by Western blot analysis. RESULTS: EGFR was detected in 60% of PR-B-positive samples and in 90.5% of PR-B-negative samples (P=.015). EGFR expression was higher in progestin-resistant KLE EC cells than in progestin-sensitive Ishikawa EC cells. In contrast, PR-B expression was higher in Ishikawa cells than KLE cells. Higher EGFR expression reduced sensitivity to progestin and decreased PR-B expression in Ishikawa cells; it also abnormally activated the MAPK signaling pathway and inhibited cell apoptosis. The EGFR tyrosine kinase-specific inhibitor AG1478 effectively inhibited the proliferation of EC cells that overexpressed EGFR. CONCLUSIONS: The current results indicated that EGFR overexpression may play an important role in reducing sensitivity to progestin treatment in EC. An EGFR tyrosine kinase-specific inhibitor may be useful in the treatment of EC.

[Biodehydrogenation of 11beta-hydroxyl melroxyprogesterone by Arthrobacter simplex UR016 in microemulsion system].

To improve mass transfer and enhance the yield for C(1,2) biodehydrogenation of steroid 11beta-hydroxyl medroxyprogesterone, we carried out the dehydrogenation reaction of 11beta-hydroxyl medroxyprogesterone in an oil-in-water (O/W) microemulsion by Arthrobacter simplex UR016. We studied the effects of system composition, dehydrogenation temperature and substrate concentration on microbial transformation. We formulated a suitable O/W microemulsion system with Arthrobacter simplex UR016 culture broth as aqueous phase, 10 g/L of edible oil as oil phase, 4 g/L of Tween-O80 and 7% (V/V) alcohol as surfactant and cosurfactant. The optimal dehydrogenation temperature was 33 degrees C. The results showed that in Tween-80/alcohol/edible oil/water microemulsion system, the hydrophobic steroid was solubilised and diffused effectively, with the maximum conversion rate of 88.6% at 46 h under 4 g/L substrate concentration, an increase of 66.2% compared to that in aqueous system. The C(1,2) biodehydrogenation of 11beta-hydroxyl medroxyprogesterone is more efficient in water-edible oil microemulsion system than in aqueous system.

Hormone-regulated expression and distribution of versican in mouse uterine tissues.

BACKGROUND: Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination. METHODS: Uteri from mice in all phases of the estrous cycle, and animals subjected to ovariectomy and hormone replacement were collected for immunoperoxidase staining for versican, as well as PCR and quantitative Real Time PCR. RESULTS: In diestrus and proestrus, VER was exclusively expressed in the endometrial stroma. In estrus and metaestrus, VER was present in both endometrial stroma and myometrium. In OVX mice, VER immunoreaction was abolished in all uterine tissues. VER expression was restored by E2, MPA and E2+MPA treatments. Real Time PCR analysis showed that VER expression increases considerably in the MPA-treated group. Analysis of mRNA identified isoforms V0, V1 and V3 in the mouse uterus. CONCLUSION: These results show that the expression of versican in uterine tissues is modulated by ovarian steroid hormones, in a tissue-specific manner. VER is induced in the myometrium exclusively by E2, whereas MPA induces VER deposition only in the endometrial stroma.

[In vitro metabolic interaction between diphenytriazol and steroid hormone drugs].

AIM: To observe the metabolic interaction between diphenytriazol and steroid hormone drugs, and provide some useful information for clinical medication. METHODS: The steroid hormone drugs which may be co-administrated with diphenytriazol were selected, such as mifepriston, estradiol, medroxyprogesterone acetate, progesterone, norethisterone and so on. Diphenytriazol was incubated with each drug in rat liver microsome. The residual concentration of diphenytriazol or steroid hormone drugs in the microsomal incubates was determined by reversed-phase high-performance liquid chromatography, separately. The inhibition constants (K(i)) for each of them were calculated. RESULTS: The inhibition constant K(is) of diphenytriazol for the metabolism of mifepristone, estradiol, medroxyprogesterone acetate, progesterone and norethisterone were (201.3 +/- 1.0), (94 +/- 4), (128.7 +/- 2.2), (64 +/- 5) and (80 +/- 4) micromol x L(-1), respectively. The inhibition constants K(i) of steroid hormone drugs for the metabolism of diphenytriazol was (66.9 +/- 2.2) micromol x L(-1) for estradiol, (60.0 +/- 2.3) micromol x L(-1) for medroxyprogesterone acetate, (163 +/- 10) micromol x L(-1) for progesterone and (88 +/- 5) micromol x L(-1) for norethisterone, respectively. CONCLUSION: Diphenytriazol shows metabolism interaction with steroid hormone drugs such as estradiol, medroxyprogesterone acetate, progesterone and norethisterone.

Membrane-initiated steroid signaling (MISS): genomic steroid action starts at the plasma membrane.

UNLABELLED: Plasma membrane (PM) steroid recognition sites are thought to be responsible only for rapid, non-genomic responses without any link to the nuclear receptor-mediated genomic effects of steroids. We focused on a PM "glucocorticoid-importer" (GC-importer) that imports GC into rat liver cells. This site interacts also with particular gestagens (progesterone, P; medroxyprogesterone, MP; ethynodiol, Ethy) and estrogens (ethinylestradiol, EE(2); mestranol), which do not bind to the nuclear GC receptor (GR). To elucidate the role of the GC-importer, we transfected a rat wild-type hepatocyte (CC-1) and a hepatoma cell line, unable to import GC (MH 3924), with a GC<-->GR-responsive luciferase (luc)-reporter gene. Selected steroids were tested for their ability to induce or inhibit luc expression. Corticosterone (B) and dexamethasone (Dex), but also the GC-antagonists cortexolone (Cortex), P and MP, induced luc. Even the PM-impermeable BSA-derivatives of B, Dex and Cortex did so to almost the same extent as the free steroids. MH 3924 cells respond stronger than CC-1 to luc inducing steroids. Luc expression was inhibited by RU 38 486, but also by EE(2) and Ethy. The thiol reactive mesylate-derivatives of B, Dex and Cortex induced to a considerably lesser extent than the free or BSA-steroids. The thiol reagent mersalyl blocks cellular entry of GC and inhibits luc induction in CC-1 cells. Incubation with EE(2) and B of PM-vesicles, isolated from liver cells, resulted in a decrease of the density of two 75 and 52kDa G-proteins reflecting a diminished exchange of GDP by GTP. CONCLUSION: the PM-residing GC-importer, now renamed "Steroid Hormone Recognition and Effector Complex" (SHREC) is an interdependent part of the complete GC signal propagation in which G-proteins are involved. Free SH-groups of SHREC are a prerequisite for genomic GC activity. Specific interactions between SHREC and GC-agonist/-antagonist trigger steroid-dependent signaling. However, import of the ligand into the cell terminates it. Thus, the PM-related non-genomic steroid responses are clearly linked to the GR-related genomic effects.

Human endometrial decidual cell-associated 11 beta-hydroxysteroid dehydrogenase expression: its potential role in implantation.

During pregnancy excess corticosteroid exposure can disturb the normal pattern of growth and differentiation of the primate fetus. This is normally prevented by the action of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which converts cortisol to its biologically inactive 11-oxo form, thereby ensuring that little or no cortisol is transferred to the fetus. During implantation, extravillous trophoblasts breech uterine vessels that are embedded in a decidual cell matrix. Through this invasive process the embryo gains requisite access to the maternal blood supply, while risking exposure to high circulating glucocorticoid levels. Thus, the expression of 11 beta-HSD by the decidual cell layer may be essential in regulating cortisol exposure of the developing embryo prior to placentation. In order to investigate the potential contribution of decidual cells to glucocorticoid metabolism, we evaluated the expression of both known 11 beta-HSD isoforms, 11 beta-HSD1, whose catalytic activity is NADP(+)-dependent, and NAD(+)-dependent 11 beta-HSD2, during decidualization of monolayers of human endometrial stromal cells. The differential actions of ovarian steroids on human endometrium are simulated in this in vitro model. Thus, progestins induce the expression of several decidualization markers in the cultured stromal cells, and consistent with its priming action in vivo, estradiol augments this expression. The results of our studies established a link between in vitro decidualization and enhanced glucocorticoid metabolizing capacity. Accordingly, the catalytic activities of both 11 beta-HSD isoforms were enhanced by incubation of the precursor stromal cells with medroxyprogesterone acetate, and further enhanced by estradiol, despite a lack of response to estradiol alone. This differential response to estradiol and progestin was reflected in parallel changes in steady state levels of 11 beta-HSD1 messenger RNA. The role of glucocorticoid metabolizing activity of the decidual cell is discussed in terms of its implications in determining the exposure of the implanting embryo to biologically active glucocorticoids.

Mass spectrometric and high-performance liquid chromatographic studies of medroxyprogesterone acetate metabolites in human plasma.

Medroxyprogesterone acetate (MPA) treatment has been shown to exert several beneficial effects in cancer patients. It has been suggested that such effects are due in part to the metabolites derived from MPA in vivo. The first results are reported on the identification of 2 alpha-hydroxy- and 21-hydroxy-MPA, 20-dihydro-MPA, 17 alpha-acetoxy-2 alpha,3 beta-dihydroxy-6 alpha-methylpregn-1,4-dien-20-one and two X,21-dihydroxy-MPAs, one of them presumably being 6 alpha-hydroxymethyl-21-hydroxy-MPA, in patient's plasma by high-performance liquid chromatographic (HPLC), gas chromatographic-mass spectrometric and NMR methods. Additionally, the presence of other metabolites such as di- and tetrahydro-MPAs and 6,21-dihydroxy-MPA, found in urine and other samples, was demonstrated in plasma. For routine clinical examinations an HPLC method is described for determination of, e.g., the unreduced MPA metabolite group in Sep-Pak-ODS column extracts of patients' plasma.

Medroxyprogesterone acetate and the nuclear uptake of testosterone and its metabolites by brain, pituitary gland and genital tract in male cynomolgus monkeys.

The synthetic progestin, medroxyprogesterone acetate (MPA), is used to treat male sex offenders, and it is also suppresses sexual activity in male monkeys. To examine the possibility that MPA may act as an anti-androgen in the primate brain, 4 intact male cynomolgus monkeys were given MPA (40 mg i.m.) once a week for 16 weeks, while 4 control males received i.m. injections of vehicle. All males were then castrated and 3 days later were given 3 mCi [3H]testosterone ([3H]T) i.v.; 1 h after injection males were killed, and radioactivity in nuclear pellets obtained from the hypothalamus (HYP), preoptic area (POA), amygdala (AMG), septum, pituitary gland and genital tract was analyzed by HPLC. Concentrations of [3H]T and [3H]dihydrotestosterone in nuclear pellets were 65-96% lower in MPA-treated males than in controls (P less than 0.001), but the aromatized metabolite, [3H]estradiol, which was the major form of radioactivity present in nuclear pellets from HYP, POA and AMG, was unchanged. There were no differences in concentrations of [3H]T in supernatants from the tissues of MPA-treated and control males. Because the reduced nuclear uptake of androgen in brain occurred in males whose androgen-dependent behavior had been suppressed by MPA treatments, it is proposed that MPA may have anti-androgenic effects at the level of the cell nucleus in brain regions that control behavior.

Uptake of medroxyprogesterone acetate by progestin and androgen target neurons in the brain and pituitary gland of male cynomolgus monkeys.

Medroxyprogesterone acetate (MPA), a synthetic progestin that reduces plasma testosterone levels, has been used in the treatment of male sex offenders. It also reduces the sexual activity of male macaques. To investigate its sites and mechanisms of action, 11 adult male cynomolgus monkeys were castrated and 7 and 21 h later were pretreated with 20 mg progesterone s.c. (Prog, n = 3), or 5 mg dihydrotestosterone propionate s.c. (DHTP, n = 3) or oil vehicle (controls, n = 5). Twenty-four hours after castration, all males were injected i.v. with 5 mCi [3H]-MPA, and killed after 60 min. Left halves of the brains were processed for thaw-mount autoradiography to identify the neurons accumulating radioactivity, and right halves were analyzed by high performance liquid chromatography (HPLC) to measure the uptake of [3H]-MPA in nuclear fractions. In males pretreated with oil, there were labeled neurons in the ventromedial nucleus (n.), arcuate n., medial preoptic n. and anterior hypothalamic area. In progesterone-pretreated males, labeling was reduced by 84-100% compared with controls (p less than 0.001), but in DHTP-pretreated males there was no effect, and labeling was not significantly different from control levels. Nuclear concentrations of [3H]-MPA measured by HPLC in controls were highest in the hypothalamus, amygdala, preoptic area and pituitary gland. Pretreatments with progesterone reduced the nuclear concentrations of [3H]-MPA in hypothalamus, preoptic area and pituitary gland by 82-95% compared with controls (p less than 0.05), but DHTP pretreatments had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Medroxyprogesterone acetate binding sites in human endometrium and endometrial cancer.

Medroxyprogesterone acetate (MPA) binding sites in both human normal endometrium and endometrial carcinoma were identified and characterized by sucrose gradient centrifugation. These binding components were divided into two classes by saturation analysis, one with high affinity and low capacity and the other with low affinity and high capacity. The concentrations of low-affinity binding sites for MPA in endometrial carcinoma were higher than those in normal endometrium (p less than 0.01). By sucrose gradient centrifugation, 4S and 8S components were observed in both high- and low-affinity binding sites of normal endometrium. These components were moved to 4S by the addition of salt. However, in endometrial carcinoma, low-affinity binding sites were displayed at about 4S under either low- or high-salt conditions. High-affinity binding sites in endometrial carcinoma had the same sedimentation patterns as in normal endometrium. An obvious difference between normal endometrium and endometrial cancer was observed in low-affinity binding sites. Our results on the binding sites for MPA suggest that low-affinity binding sites may be related to the response of endometrial cancer to high-dose MPA treatment.

Comparison of in vivo bioavailability of progestational agents into the rat uterus and liver and the effect of plasma protein binding.

The in vivo bioavailabilities of three clinically available progestational agents were evaluated with a previously described rat model. With this model a single-injection, double-isotope technique was performed to calculate and compare the unidirectional extractions of progesterone, 19-nortestosterone, and medroxyprogesterone acetate into the rat uterus and liver. To assess the role of plasma protein binding in the extraction of these agents, steroids were presented in four different vehicles: (1) Ringer's solution, 0.1% bovine serum albumin; (2) Ringer's solution, 4% bovine serum albumin; (3) Ringer's solution, 0.8 mg/ml, alpha 1-acid glycoprotein; (4) human pregnancy serum. The results revealed that liver extraction always exceeded uterine extraction for each progestin, regardless of the vehicle, and that liver extraction was approximately 100% for all steroids. With regard to the uterus, when binding proteins were not present in the injectate, the extraction of the three steroids was similar; the uterine vasculature was relatively permeable to these progestins, and bovine serum albumin and alpha 1-acid glycoprotein had no major effect on the uptake into the uterus. However, when human pregnancy serum was in the injectate, the extractions of progesterone and 19-nortestosterone into the rat uterus were significantly diminished. In contrast, pregnancy serum had no effect on the uptake of medroxyprogesterone acetate into the uterus, with the extraction equal to that of Ringer's solution alone. This suggests that, regardless of potential binding proteins, medroxyprogesterone acetate displays greater bioavailability than that of the other progestogens studied.

In vitro binding of progesterone, cronolone and medroxyprogesterone acetate to uterine progesterone receptors of sheep, rabbit and mouse.

Various aspects of the binding of the synthetic progesteongens, cronolone (9 alpha-fluoro-11 beta-hydroxy-17 alpha-acetoxypregn-4-ene-3,20-dione) and medroxyprogesterone acetate (6 alpha-methyl-17 alpha-acetoxypregn-4-ene-3,20-dione, MAP) to uterine cytosol progesterone receptors of the sheep, rabbit and mouse were studied, in an attempt to explain interesting species differences in the biological activity of these steroids. For the sheep, data for binding-site concentration, relative binding affinity (RBA), dissociation constant (Kd) and rates of association and dissociation indicate specific binding of cronolone to the progesterone receptor and these would seem to explain in part the high progestational activity of cronolone in this species. By contrast, with the mouse, there was only a low level of specific binding of cronolone and this appears to explain its inability to maintain pregnancy in this species. Results for the binding activity of cronolone in rabbit uterus were similar to those for the sheep and thus inability of cronolone to maintain pregnancy in the rabbit is not explained by a failure to bind the progesterone receptor. Species differences in binding to the progesterone receptor were also seen with MAP where the RBA, with respect to progesterone, was high in the sheep and rabbit and lower in the mouse. The results, however, do not relate directly to the progestational activity of MAP in these species. Overall, the data indicate that species differences in the binding activity of steroid receptors constitute one factor that causes species-dependent variation in biological responses to progestogens.

Pharmacokinetics and metabolism of medroxyprogesterone acetate in patients with advanced breast cancer.

The pharmacokinetics and metabolism of medroxyprogesterone acetate (MPA) were studied in patients with advanced breast cancer after i.v. injection and oral administration of [3H]MPA. MPA was distributed very rapidly into three compartments after i.v. injections, revealing half-lives of 4-7 h. Using a nonlinear model fitting metabolic clearance rates (MCR) were found to be 652 1/day before and 601 1/day during MPA treatment, and distribution volumes (V0) 5.9 and 3.41 respectively. The major metabolite of MPA following i.v. injection was a glucuronide of MPA, presumably of the 3-enol form. After oral administration the radioactivity in serum increased rapidly and reached a plateau of about 1% of the dose per litre serum after approx 2 h. About 80-90% of the radioactivity was found in the water phase after hexane extraction, persumably as glucuronides of metabolites more polar than MPA. Radioimmunoassay (RIA) of MPA in untreated serum samples showed 3-8-fold greater MPA values as compared to measurements in hexane extracts of serum. Ethanol extraction did not remove these interfering substances. Extraction of serum with a low polar solvent before RIA of MPA is essential in order to prevent great overestimation, as the glucuronidated polar metabolites most likely will crossreact in an assay with an antiserum raised against a MPA-3-O-carboximethyloxime coupled to bovine serum albumin.

Amniotic fluid and decidual prolactin during pregnancy in rhesus macaques.

In rhesus macaques, the concentration of immunoreactive prolactin in the amniotic fluid remains low during most of the first trimester of pregnancy and then increases abruptly at 60-80 days of gestation. During the second half of pregnancy, large amounts of prolactin accumulate in the amniotic fluid. Much of this amniotic fluid prolactin may originate from the superficial endometrium (decidua). This hypothesis is supported by the increasing amounts of decidual prolactin (dPRL) measured in endometrium obtained at early (50 days), mid-(80 days), and late (greater than or equal to 150 days) gestation. In culture, late pregnancy endometrium released more dPRL than did early pregnancy endometrium. When tissues were cultured in medium without progesterone, the amounts of dPRL measured in the medium declined steadily over 6 days, regardless of the gestational age of the endometrium. dPRL was consistently measured in medium harvested from cultures that received either progesterone or medroxyprogesterone; however, progesterone did not induce an increase in the amounts of dPRL released by cultures prepared from early pregnancy endometrium. This suggests that factors in addition to progesterone may stimulate the increase in dPRL that occurs at midgestation in rhesus macaques.

[Growth inhibition by progestins in human endometrial cancer cells with progesterone receptors].

The presence of estrogen-independent progesterone receptors (PR) was demonstrated in a subline of a human endometrial cancer cell line, Ishikawa cells. Scatchard plot analysis of cytoplasmic binding data in a subline (IK-90) revealed a high affinity binding site for promegestone (Kd, 1.0 nM) with maximum binding sites of 158 fmol/mg protein. Competition experiments showed a binding specificity similar to that of typical PR. By low-salt sucrose gradient centrifugation, radioactive 8S and 4S peaks were found. The addition of 1 microM progesterone in culture medium resulted in a rapid nuclear translocation of cytoplasmic PR. Accumulation of glycogen in cytoplasm of the cells in response to 0.1 microM promegestone was observed by periodic acid-Schiff staining. Addition of various concentrations (1 nM-1 microM) of promegestone reduced the cell growth in a dose-dependent manner. The growth inhibition by promegestone was totally prevented by the concomitant addition of equimolar RU 486, a progestin antagonist. The other steroids including tamoxifen, cortisol, and testosterone had no significant effects on the growth of the cells. The growth-inhibitory effect of progestin on cultured cancer cells from human endometrial adenocarcinomas obtained by hysterectomy was also investigated. Addition of medroxyprogesterone acetate (1 nM-1 microM) caused a marked decrease in [3H]thymidine incorporation in cultured cancer cells from tumors with PR. From the viewpoint obtained in the present studies using both IK-90 cells and endometrial cancer cells in primary culture, it can be concluded that progestins produce regression of endometrial cancer directly via the PR system.

Medroxyprogesterone acetate: variation in serum concentrations achieved with three commercially available preparations.

Twenty-nine females with metastatic or locally recurrent carcinoma of the breast were treated orally with 1 g of medroxyprogesterone acetate (MPA) daily. This was used as a second- or third-line treatment. Serum concentration of MPA was measured over a 28-day period. We have demonstrated a significantly greater area-under-the-concentration-time curve, peak, and steady-state MPA concentration for Provera at 100- and 200-mg tablets (Upjohn) than for Farlutal at 500-mg tablets (Farmitalia). Relative bioavailability of preparations should be considered when prescribing or assessing treatment results when MPA is used.

Medroxyprogesterone acetate: receptor binding and correlated effects on steroidogenesis in rat granulosa cells.

Medroxyprogesterone acetate (MPA), a widely used synthetic steroid, was studied to determine both its effects on steroid receptors and steroidogenesis in the well-characterized rat ovarian granulosa cell model. Initial receptor binding studies showed MPA was as potent as progesterone and 10-fold less potent than R-5020 (an active synthetic progestin) in binding to progesterone cytosolic receptors in rat ovarian granulosa cells. MPA was 20-fold less potent than testosterone, and 10-fold less potent than dexamethasone in binding to the androgen and glucocorticoid cytosolic receptors, respectively. The binding of MPA to progestrone, androgen and glucocorticoid receptors predicted direct effects of MPA on FSH-stimulated estrogen (E), progesterone (P), and 20 alpha-dihydroprogesterone (DHP) production by cultured rat ovarian granulosa cells. MPA at 10(-7) to 10(-6) M significantly augmented FSH-stimulated P and DHP production (a previously documented progestin, androgen and glucocorticoid effect). This augmentation was blocked by the concurrent addition to cell culture of 10-fold excess RU-486 (a potent anti-progestin and anti-glucocorticoid). At concentrations greater than 10(-6) M, MPA inhibited the production of P and DHP (a progestin effect), and the production of E (a progestin and glucocorticoid effect). MPA, structurally a progestin, has complex steroid hormone effects predicted by its interaction with progesterone, androgen and glucocorticoid receptors.