Steroid hormone receptors

Cochlear Glucocorticoid Receptor and Serum Corticosterone Expression in a Rodent Model of Noise-induced Hearing Loss: Comparison of Timing of Dexamethasone Administration

Glucocorticoid (GC) is a steroid hormone secreted from the adrenal cortex in response to stress, which acts by binding to cytoplasmic glucocorticoid receptors (GRs). Dexamethasone (DEX) is a synthetic GC exhibiting immunosuppressive effects in both human and rodent models of hearing loss. While clinical evidence has shown the effectiveness of DEX for treatment of various inner ear diseases, its mechanisms of action and the optimal timing of treatment are not well understood. In the present study, intergroup comparisons were conducted based on the time point of treatment with DEX: (1) pretreatment; (2) posttreatment; and (3) pre&post-noise. The pre&post DEX treatment group showed a significant improvement in threshold shift at 1 day post-noise exposure as compared to the TTS (transient threshold shift)-only group at 8 and 16 kHz. Both TTS and PTS (permanent threshold shift) significantly reduced cochlear GR mRNA expression and increased serum corticosterone and cochlear inflammatory cytokines. The pre&post DEX treatment group showed a significant decrease in serum corticosterone level as compared to other DEX treatment groups and TTS-treated group at 3 days after acoustic trauma. Our results suggest that the timing of DEX administration differentially modulates systemic steroid levels, GR expression and cochlear cytokine expression.

Estrogen and Progesterone Binding Proteins in Human Colorectal Cancer. A Preliminary Characterization of Estradiol Receptor

Estradiol receptor (ER) and progesterone receptor (PgR) were assayed in tumors from 20 patients with primary colorectal cancer. Ten of 20 tumors contained high affinity sites for 17β-estradiol and progesterone. The highest concentration of ER was 56 fmol/mg of protein. The ER dissociation constant ranged from 1.6 × 10−10 M to 8 × 10−10 M (mean 4.6 ± 2.6). The highest concentration of PgR was 42 fmol/mg of protein. The PgR dissociation constant ranged from 3 × 10−9 to 9 × 10−9 M (mean 5.65 ± 2.1). Four out of 20 specimens analyzed were from male patients and all resulted negative for both receptors. Sixty per cent of ER positive tumors were also PgR positive, whereas only 20 % of ER negative were PgR positive. Sucrose gradient centrifugation showed that cytoplasmic ER of colorectal cancer sedimented at 3 S in the absence of protease inhibitors and at 4.5 S in the presence of 1 mM phenylmethylsulphonyl fluoride (PMSF) both in low and in high ionic strength. When chromatographed on Sephadex G-200 almost all ER was quantitatively recovered in the included fractions. Molecular weights of ER eluted from Sephadex G-200 ranged from 90,000 to 50,000 daltons. Elution profile and molecular weight heterogeneity suggest that, in spite of the presence of PMSF, there is a limited proteolysis of ER. Partially purified colorectal cancer ER did not bind to sepharose-heparin. The isoelectric point of ER was 6.4–6.5.

Estrogen Receptors and Post-Receptor Markers in Human Breast Cancer: A Reappraisal

Several major defects in the estrogen receptor pathway have been evidenced in most human breast cancers by an immunofluorescence tracing of estradiol receptor complexes at the single cell level. Endogenous peroxidase seems a reliable postreceptor marker for estrogen-sensitive breast cancer cells. Since almost all human breast cancers appear to include both hormone-sensitive and autonomous cell populations, a combined use of endocrine and cytotoxic regimens is urged. The hormonal regulation of tumor growth parameters could be exploited in order to achieve a maximum recruitment of synchronized tumor cells at risk to chemotherapy.

Mammary gland: From embryogenesis to adult life

The aim of this review is to focus on the molecular factors that ensure the optimal development and maintenance of the mammary gland thanks to their integration and coordination. The development of the mammary gland is supported, not only by endocrine signals, but also by regulatory molecules, which are able to integrate signals from the surrounding microenvironment. A major role is certainly played by homeotic genes, but their incorrect expression during the spatiotemporal regulation of proliferative, functional and differentiation cycles of the mammary gland, may result in the onset of neoplastic processes. Attention is directed also to the endocrine aspects and sexual dimorphism of mammary gland development, as well as the role played by ovarian steroids and their receptors in adult life.

Understanding nuclear receptors using computational methods

Nuclear receptors (NRs) are important targets for therapeutic drugs. NRs regulate transcriptional activities through binding to ligands and interacting with several regulating proteins. Computational methods can provide insights into essential ligand-receptor and protein-protein interactions. These in turn have facilitated the discovery of novel agonists and antagonists with high affinity and specificity as well as have aided in the prediction of toxic side effects of drugs by identifying possible off-target interactions. Here, we review the application of computational methods toward several clinically important NRs (with special emphasis on PXR) and discuss their use for screening and predicting the toxic side effects of xenobiotics.

Steroid and peptide control mechanisms in membrane of Xenopus laevis oocytes resuming meiotic division

Stage 5-6 Xenopus laevis oocytes are arrested in prophase of the first meiotic division, and can be studied in vitro after removal from their follicle cell environment. While they do not mature spontaneously, they demonstrate germinal vesicle (nucleus) breakdown (GVBD) if exposed to approximately 1 microM-progesterone (the hormone released in vivo at the time of ovulation and maturation). The oocytes' then become eggs ready to be fertilized. The progesterone-oocyte interaction, contrary to what is observed in all endocrine steroid target organs so far studied, takes place at the surface membrane level and is not narrowly progesterone-specific, since other hormones such as cortisol or testosterone can also cause resumption of meiosis in vitro. This is the first description of such a paracrine steroid system, which depends however on a receptor mechanism, as indicated by physicochemical experiments, studies with antagonistic (competitive) steroids, and cell-free specific inhibitory effects on membrane-bound adenylate cyclase. It was found that insulin and related growth factors (mitosis-stimulating activity, MSA; insulin-like growth factor, IGF) are also reinitiators of meiosis. Insulin also potentiates the effects of low progesterone concentration (approximately 1 nM) in completely denuded oocytes (free of the vitelline membrane). From these observations it is suggested that there may be a physiological, cooperative involvement of a steroid (progesterone) and an insulin-like peptide factor within the ovaries which promotes oocyte maturation in vivo. The molecular mechanisms of the hormone-dependent changes in cyclic AMP and Ca2+ remain to be elucidated in detail, as well as the respective roles of these two sets of metabolic events.

Fatos e mitos sobre imunomoduladores

O objetivo deste artigo é discutir alguns fatos dos imunomoduladores modernos que podem ser úteis para o dermatologista clínico. Outro objetivo importante é o de dissipar mitos que possam ter impacto negativo no uso dessas drogas pelo clínico. O foco inicial está em imunomoduladores estimuladores que podem conduzir à acentuação da resposta normal das células imunocompetentes. Para tanto, diversos aspectos associados à regulação do sistema imune e às vias regulatórias das células do sistema imune são mencionados. Discutem-se a regulação aberrante e seu impacto no sistema imune e examina-se a classe de drogas imunossupressoras que têm sua função bem estabelecida. Diversas drogas não foram mencionadas. A razão para isso é o foco do artigo que pretende cobrir os fatos bem estabelecidos ou os mitos que as novas evidências científicas modificaram. Com esse padrão em mente, é provável que exista uma quantidade considerável de similaridade nos conceitos, uma vez que descrevem drogas imunomoduladoras. Nesse contexto, a intenção de fornecer novas perspectivas de como o sistema imune pode ser modulado por essas drogas supera esse problema.

Sex steroid effects at target tissues: mechanisms of action

Our understanding of the mechanisms of sex hormone action has changed dramatically over the last 10 years. Estrogens, progestins, and androgens are the steroid hormones that modulate reproductive function. Recent data have shown that many other tissues are targets of sex hormones in addition to classical reproductive organs. This review outlines new advances in our understanding of the spectrum of steroid hormone ligands, newly recognized target tissues, structure-function relationships of steroid receptors, and, finally, their genomic and nongenomic actions. Sex-based specific effects are often related to the different steroid hormone mileu in men compared with women. Understanding the mechanisms of sex steroid action gives insight into the differences in normal physiology and disease states.

Regulation of the content of progesterone and estrogen receptors, and their cofactors SRC-1 and SMRT by the 26S proteasome in the rat brain during the estrous cycle

In this work we have determined the role of the 26S proteasome in the regulation of the content of progesterone receptors (PR-A and PR-B), estrogen receptors (ER-alpha and ER-beta), the coactivator SRC-1 and the corepressor SMRT in the rat brain during the estrous cycle. The 26S proteasome inhibitor MG132 was injected once into the lateral ventricle on proestrous day; and 24h later, on estrous day we evaluated the content of PR and ER isoforms, SRC-1 and SMRT in the hypothalamus, the preoptic area and the hippocampus by Western blot. A significant increase in the content of both PR isoforms, ER-beta and SRC-1 was observed after the administration of MG132 in the three studied cerebral regions. SMRT content was increased in the hypothalamus and the preoptic area and a significant increase in ER-alpha content was only observed in the preoptic area. These results suggest that essential proteins that participate in progesterone and estrogen actions in the brain should be regulated by the 26S proteasome in a tissue-specific manner in physiological conditions.

Natural sex steroids and their xenobiotic analogs in animal production: growth, carcass quality, pharmacokinetics, metabolism, mode of action, residues, methods, and epidemiology

Natural and xenobiotic compounds having sex-related actions have long been used for growth promotion and various changes in carcass quality in meat animals. The first compounds used were synthetic estrogens; however, later on a whole battery of compounds having androgenic, and progestogenic actions have also been involved. In surveying the effects of these compounds in meat-producing animals, it became clear that these drugs increase the growth rate of the treated animals and bring about changes in the carcass that are generally characterized by lower fat content and more lean mass. Extensive studies undertaken in various countries, including the European Economic Community (EEC), have shown that if used according to good husbandry practices, the meat from treated animals does not have excessive amounts of residues compared with the endogenous amount of steroid production in the animals in question and also in human beings. The banning of these compounds in the European community brought a new phenomenon of illegal or black market cocktails. These mixtures of anabolic steroids are injected into the body of the animals rather than implanted in the ears, which is the normal practice in countries where they have not yet been banned. Several screening and confirmatory methods are now available for monitoring programs. However, these programs need excessive resources in terms of manpower, funds, and proper legislation, which in underdeveloped countries is questionable, particularly in the absence of strong scientific evidence for the exercise.

Effects of progesterone administered by nasal spray on the human postmenopausal endometrium

The aim of the study was to assess the effectiveness of progesterone (P) administered by nasal spray (NS) in inducing secretory changes within estrogen and non-estrogen primed postmenopausal endometrium. Ten healthy post-menopausal women before vaginal hysterectomy for prolapse were randomly treated by either oral estrogens for 3-4 weeks combined for the last 5-7 days with nasally administered P at the daily dose of 34 mg, or by only P for 6 days. Endometrial samples were taken before P administration and 8 h after the last dose. In the group not treated with estrogens, P did not induce significant secretory changes in any case except one which showed a proliferative endometrial pattern at the first evaluation. In the group treated with estrogens, in all the cases after P administration clear secretory changes (abundant vacuoles, endoluminal secretion) occurred. It is possible to conclude that P administered by NS exerts an end-organ effect within the endometrium of postmenopausal women pretreated with estrogens.

Relationship between steroid levels in peripheral serum and uterine tissue during pseudopregnancy in rabbit

Determination of the main C21, C19 and C18 steroids in peripheral serum and uterine tissue was made to study the relationships of the steroids during pseudopregnancy in the rabbit. Tissue and serum progesterone levels rose significantly (P < 0.01) from estrus to Day 9 and then decreased by 81% (tissue) and 57% (serum) at Day 15, while pregnenolone levels in uterine tissue and serum remained unaffected. Estradiol serum levels remained fairly stable, whereas its concentration in uterine tissue decreased after estrus by 85%, followed by a significant (P < 0.05) increase from Day 9. Most of the C19 steroid values in the uterine tissue and in the serum were generally at levels below or near the limit of detection and did not vary significantly. Since progesterone and estradiol levels were high and/or varied significantly in tissue throughout pseudopregnancy, and since androgens were produced in small amounts, it is suggested that androgens might not play a significant role in uterine tissue during pseudopregnancy.

Testosterone-induced responsiveness to androgen in Shionogi mouse carcinoma cells

Primary cell cultures from an androgen-dependent mouse mammary carcinoma, the Shionogi-SC 115 tumor, were cultured in the presence or absence of testosterone (50 nM). Characteristic changes in cellular morphology and cell growth were observed according to the presence or absence of the androgen. In testosterone-containing medium, cells formed individual clones, piling up one over another and showed no contact inhibition, whereas in the absence of the androgen, cells had a flattened morphology, they grew in a monolayer and cell multiplication was reduced. The testosterone-dependent changes were observed in culture as long as cells were maintained in androgen-containing medium. Only a few (3-5) days of culture in the absence of testosterone rendered cells irreversibly unresponsive to the androgen, and they could no longer produce tumours after inoculation in the host animal. Cellular proteins were analysed after culture in the presence or absence of testosterone. After [35S]methionine labelling of cells and SDS-PAGE of the cytosol, several proteins were specifically synthesized in the presence of testosterone, predominantly a 45 kD protein, which was not seen in the absence of the androgen. Conversely, a protein of 35 kD present in absence of the hormone disappeared in the presence of testosterone. The anti-androgen cyproterone acetate inhibited the characteristic cellular morphology, cell proliferation and protein synthesis observed in the presence of the the androgen. The antiprogestin and anti-glucocorticosteroid RU 486 also showed limited anti-androgen activity. The concentration of specific androgen receptor-binding sites did not change significantly after 3 months of culture with or without testosterone, i.e., in responsive and unresponsive cells.

Enhanced inhibition of estrogen receptor nuclear binding in the uterus of aged mice

We have studied why uteri from aging mice show a decrease nuclear concentration of estrogen receptors (UER). While 50-60% of available cytosolic UER from ovariectomized (OVX) mice aged 4-8 months, upon physiochemical activation, are able to bind either to DNA-cellulose or nuclear suspensions from young animals, only 20-30% of comparable concentrations of cytosolic UER from mice aged 15-18 months did so under identical experimental conditions. Nuclear dilutions with uterine cytosolic fractions from estrogen treated OVX mice prior to determination of [3H] UER binding sites in nuclear suspensions decreased the number of nuclear ER sites in both age groups. However, we observed that cytosols from aged animals showed a greater ability to prevent [3H]E2 binding to nuclear sites when compared to young ones (inhibition index: 0.286 +/- 0.013 (SE) vs. 0.137 +/- 0.025, P less than 0.05). These changes occur independently of protein concentration and result from dilution of a specific endogenous inhibitor of [3H]E2 binding to nuclear sites. The significance of these observed differences is discussed.

Transformation of the chick oviduct progesterone receptor in the absence of hormone

Chicken oviduct progesterone receptor in cytosol was found to be transformed from the 8S to 4S form by incubation at 25 degrees C as well as by 0.3 M KCl in the absence of hormone. Heat transformation of ligand-free receptor took place at a much slower rate than that of ligand-bound receptor. The eventual percentage of transformation, however, was almost the same. The 4S form of the receptor transformed by KCl in the absence of hormone could bind to DNA-cellulose, but not to nuclei. However, upon exposure it acquired the ability to bind to nuclei. It was shown that the transformed ligand-free receptor could bind to progesterone to form the normal activated steroid-receptor complex. Conversely, when activated 4S progesterone-receptor complex was treated with DCC to peel off the hormone, a resulting ligand-free receptor was formed which behaved just like the KCl-transformed receptor in the absence of hormone.

Cortisol effect on (Na+ + K+)-stimulated ATPase activity and on bilayer fluidity of dog brain synaptosomal plasma membranes

The binding of [14C]cortisol into dog brain synaptosomal plasma membranes (SPM) follows an exponential path described by the general formula y = a.ebx. The specific activity of the SPM-bound (Na+ + K+)-stimulated ATPase was linearly increased at different concentrations of cortisol. Changes in the allosteric properties of (Na+ + K+)-stimulated ATPase by fluoride (F-) (i.e. changes of Hill coefficients) indicate that cortisol increases the membrane fluidity. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene-labeled SPM decreased in cortisol treated SPM compared to untreated (control) SPM, which is consistent with a general increase in membrane fluidity. This increase of fluidity by cortisol may play a role in the physiological effects of this hormone in the brain.

Covalent chromatography by thiol-disulfide interchange of the highly-purified non-transformed rat liver glucocorticoid-receptor

Highly-purified non-transformed rat liver [3H]triamcinolone acetonide-receptor complex was shown to be covalently adsorbed on activated thiol sepharose 4B, a reactive sulfhydryl matrice. Elution by mercaptoethanol in excess and inhibition of binding by previous treatment of the complex with N-ethylmaleimide clearly demonstrated the specificity of the binding by thiol disulfide interchange. The transformed [3H]triamcinolone acetonide-receptor complex, partially purified by DNA-cellulose chromatography, was also retained on activated thiol sepharose 4B. The physicochemical characteristics of both the transformed and non-transformed glucocorticoid receptor complexes eluted from the covalent chromatography column were studied by HP size exclusion chromatography on a TSK G 3000 SW column and were found to be identical to those of the starting complexes. These results provide direct evidence for accessible sulfhydryl groups on the glucocorticoid receptor complex surface, probably distinct from the steroid binding essential sulfhydryl group.

Estradiol and progesterone receptors in normal and pathologic colonic mucosa in humans

The presence of estradiol (E) and progesterone (Pg) receptors (R) has been demonstrated also in normal and neoplastic tissues known to be hormone-independent and in particular in primitive colonic cancer, and, possibly, in healthy colonic mucosa. In this study endoscopic and surgical colonic mucosa specimens from 55 subjects were analyzed and divided as follows: 21 samples from healthy subjects, 12 normal mucosa samples from subjects affected with colonic cancer, 8 adenomatous polyps specimens, 5 samples from ulcerative colitis drawn on areas showing macroscopic lesions and 9 colonic cancer specimens. In the control group we have observed 6 cases positive for ER (28.6%) and 2 positive for PgR (14.3%). Six normal mucosa specimens from subjects affected with colonic cancer were found to be positive for ER (50%) and 2 for PgR (16.7%). Five colonic cancers resulted ER positive (55.5%) and 4 PgR positive (44.4%). Four polyps were ER positive (50%) and 3 PgR positive (37.5%); in this group only one subject showed positive binding in the surrounding normal tissue. These data confirm the presence of ER and PgR in colonic cancer and colonic adenomas (so-called precancerous disease); in these subjects the finding of steroid receptors also in normal mucosa suggests that the presence of steroid binding could be considered as a marker of a precancerous condition.

The "dysharmonic luteal phase" syndrome: endometrial progesterone receptor and estradiol dehydrogenase

The dysharmonic luteal phase (DLP) syndrome is defined by delayed endometrial maturation despite normal plasma progesterone (P) values. In ten patients with DLP the actual date of the endometrial biopsy, dated retrospectively, was 24.7 +/- 2.3 days, whereas the histologic date was 20.0 +/- 2.6 days. The concentration of cytosolic P receptor in DLP endometrium tended to be lower, whereas the concentration of nuclear receptor was significantly higher in DLP than in seven matched patients with normal luteal phases. Endometrial estradiol-dehydrogenase activities were identical in both groups. The DLP syndrome cannot be explained by a decreased sensitivity of the endometrium to P and is probably merely functional in nature.

Ultrastructural evidence of progesterone receptor by immunochemistry

Antiserum against purified chick oviduct non-transformed "8S"-progesterone receptor has been used for detecting progesterone receptor in rat pituitary cells at the ultrastructural level after immunochemical reaction according to Sternberger. In prepubertal (21-day-old) and adult (diestrus) female rats, the gonadotropic, lactotropic and somatotropic cells were positive, but not the corticotropic and thyreotropic cells. In all positive cases, the progesterone receptor-like antigen was found in both the cytoplasm and the nucleus. Two hours after progesterone administration to immature rats, there was an increase of receptor-like antigen in nuclei of gonadotropic cells. These results and the immunological controls related to antibody specificity give the first evidence of progesterone receptor at the ultrastructural level. They remarkably show that its distribution in pituitary cells parallels the distribution of the estradiol receptor.

Chick oviduct progesterone receptor: structure, immunology, function

Analysis of the purified chick oviduct progesterone receptor using biochemical and immunological approaches indicates that while the 'activated' receptor ('4S') is a mixture of two progestin-binding polypeptides, 'A' (Mr approximately 79 kDa) and 'B' (Mr approximately 110 kDa), the non-activated receptor ('8S') is a population of complexes containing a hormone-binding polypeptide (A or B, but probably not both) bound to a non-hormone-binding protein (Mr approximately 90 kDa). Two molecules of the 90 kDa protein appear to be present in each '8S' receptor molecule. The 90 kDa protein is also associated with the non-activated forms of receptors of other steroid hormones in the chick. Molybdate stabilizes the non-activated receptors, probably by forming weak coordination bonds with radicals provided by the subunits of the '8S' structure. Activation implies separation of the subunits, without a change in their primary structure, and does not require intervention of any protein other than those present in the '8S' receptor form. The presence of ligand at the binding site accelerates the activation process but, in vitro, is not necessary for it to occur. Unlike the non-activated form, activated receptors bind to the cell nuclei. However, histological studies with anti-progesterone receptor antibodies indicate that in the non-hormone-exposed tissue the (non-activated) receptors could be localized in the nuclei.

DNA binding properties of glucocorticosteroid receptors bound to the steroid antagonist RU-486

RU-486 is an anti-fertility steroid which also has anti-glucocorticosteroid effects. RU-486 is shown to be a strong antagonist of the glucocorticosteroid-induced cytolytic response of the murine thymoma lines W7TB and T1M1b , and of the induction of mouse mammary tumor virus (MMTV) mRNA in T1M1b cells. The glucocorticosteroid receptor of W7 cells has high affinity for RU-486 (Kd = 3 X 10(-9) M) but the complex formed has low nuclear transfer capacity. Binding of RU-486, as compared with the glucocorticosteroid agonist triamcinolone acetonide, to mouse receptor results in a decreased affinity for DNA in general and a reduced specific recognition of a site in the promoter region of MMTV proviral DNA. The RU-486 complex formed with rat liver receptor exhibits the same behavior; in addition, it is shown that only a fraction of these complexes are activated by temperature and these form highly salt-sensitive interactions with DNA. These results indicate that the binding of RU-486 to glucocorticosteroid receptors mimics pharmacologically the properties of a class of receptor variants (nt-) which are non-functional and have reduced nuclear transfer and altered DNA binding capacity. These results substantiate the importance of DNA binding in receptor function.

Anti-steroid action in cultured L-929 mouse fibroblasts

L-929 mouse fibroblast growth is arrested by the glucocorticosteroid dexamethasone (dex), which also decreases adhesiveness to culture plates. Both dex effects were abolished when RU 486, a new synthetic anti-hormonal steroid, was added to the culture medium. Using [3H]RU 486, binding studies revealed that RU 486 bound approximately 25,000 sites/cell of the glucocorticosteroid receptor (GR) with affinity higher than that of dex and translocated GR to the nucleus. However, the distribution of steroid-receptor complexes between cytosol and nuclei was different for the agonist and the antagonist, with more nuclear accumulation in the case of dex. Estradiol increases L-929 cell growth and adhesiveness to culture plates, but not if the anti-estrogen tamoxifen (tam) was added. These observations initially made in serum containing medium, were confirmed in serum-free, chemically defined culture medium (SF). In SF medium, tam (1 microM) provoked death of most L-929 cells after 10 days of culture, leading to the selection of a variant clone LB of tam-resistant cells. Tam binds to the estrogen receptor (ER), but with less affinity than estradiol. ER concentration, estimated by the binding of 4-hydroxytamoxifen (OH-tam) and of estradiol was lower in LB cells than in original tam-sensitive L-929 cells. The concentration of specific anti-estrogen binding sites in the particulate fraction of the cells, measured by OH-tam binding, non competed by estradiol, was also significantly diminished in tam-resistant LB cells.

RU 38486: potent antiglucocorticoid activity correlated with strong binding to the cytosolic glucocorticoid receptor followed by an impaired activation

In order to explain the potent antiglucocorticoid activity of RU 38486 and the absence of agonist effect in spite of its very strong interaction with the cytoplasmic glucocorticoid receptor (GR), we investigated the compound's ability to promote GR "activation" and nuclear translocation. We have compared the dissociation-rates of the "non-activated" (molybdate stabilized) and of the "activated" (25 degrees C pre-heated) GR complexes formed either with [3H]RU 38486 or with different tritiated glucocorticoid agonists. While agonists dissociated more slowly from the "activated" than from the "non-activated" complex, RU 38486 dissociated much faster from the "activated" than from the "native" receptor. This difference of activation was confirmed in a DNA-cellulose binding assay. The affinity of the "activated" RU 38486-GR complex for DNA was much lower than that of the dexamethasone-GR complex. Finally, the in vitro nuclear uptake of [3H]RU 38486 was compared with that of [3H]dexamethasone after incubation with thymus minces at 25 or 37 degrees C. A very weak or nearly undetectable level of specific uptake of [3H]RU 38486 was observed in purified nuclei, whatever the concentration or the time of incubation used. These observations suggest that while glucocorticoid agonists form with the non-activated receptor a complex able to be activated into a more stable form (lower k-1), RU 38486 interacts strongly with the non-activated receptor (impeding the binding of DM) but the complex is "transformed" by heat to a less stable form (higher k-1), unable to translocate properly into the nucleus in order to trigger a glucocorticoid response.

Localization of estrogen receptor regulatory factor in the uterine nucleus

The objective of this study was to determine whether progesterone-induced estrogen receptor regulatory factor (ReRF) is a component of hamster uterine nuclei or a cytoplasmic contaminant of the nuclear fraction. Crude uterine nuclei were prepared in low salt buffer and were purified by either the hexylene glycol method or an isotonic sucrose-Triton X-100 procedure. ReRF activity was measured as a net percentage increase in estrogen receptor inactivation after incubation of a 0.5 M KCl nuclear extract at 36 degrees C for 30 min. Progesterone treatment (5 mg/kg, s.c. in oil, 2 h) increased net receptor inactivation to the same extent (9-12% net increase) in extract made from each nuclear preparation. Extensive washing of nuclei caused a progressive decline in recovery of ReRF activity, in parallel with the behavior of KCl-extractable nuclear protein and estrogen receptor. These results demonstrate that ReRF is a loosely bound component of the uterine nucleus.

Titratable effects of p-chloromercuriphenyl sulfonate, a thiol-attacking reagent, on glucocorticoid receptor binding

Cytosol prepared from cultured AtT-20 mouse pituitary cells or mouse liver was treated with concentrations of p-chloromercuriphenyl sulfonate (PCMPS) which reduced but did not abolish receptor-binding activity. Scatchard analysis of triamcinolone acetonide binding to the treated cytosol showed that the PCMPS effect was caused by a reduction of binding affinity with little effect on the apparent binding site concentration. The effect on affinity was dose-dependent. Binding specificity appeared unaffected since the relative abilities of triamcinolone acetonide, dexamethasone, cortisol, progesterone, and corticosterone to compete with labeled triamcinolone were similar at various PCMPS concentrations which caused a progressive reduction of detectable cytosol binding. The PCMPS effect was reversible since cytosol treated with up to 200 microM PCMPS followed by dithiothreitol 15 min later showed nearly complete recovery of binding sites (62-100%). The possibility that several sulfhydryl groups were involved in this phenomenon was further explored in experiments using AtT-20 cytosol labeled with [3H]dexamethasone-mesylate, a glucocorticoid affinity label which binds covalently to sulfhydryl groups. Chromatography of dexamethasone-mesylate labeled receptor on a sulfhydryl affinity column resulted in binding, indicating that the receptor had at least two sulfhydryl groups, one bound to the mesylate moiety of the steroid and the other capable of binding to the affinity column.

Similarities and differences of the binding of estradiol and 4-hydroxytamoxifen (an antiestrogen) in the chick oviduct cytosol

The binding characteristics of [3H]estradiol and 4-[3H] hydroxytamoxifen (a powerful estradiol antagonist) in the chick oviduct cytosol was analyzed by sucrose gradient centrifugation and dissociation kinetics experiments at 28 degrees C. Heating the cytoplasmic estradiol-estrogen receptor complexes led to the 'transformation' of the receptor; as with the estrogen receptor in other target tissues and species, the transformed receptor sedimented in the 5 S region of sucrose gradients containing 0.4 M KCl and had a slower rate of dissociation of bound estradiol. Upon heating, the cytoplasmic 4-hydroxytamoxifen complexes also appeared to undergo similar changes in their physical states as analyzed by sedimentation rates and dissociation kinetics, and we conclude that antiestrogen can transform the receptor. Sodium molybdate inhibited the temperature mediated changes with both estrogen and antiestrogen complexes. Slight but consistent differences in the sedimentation coefficient and rate of ligand dissociation were observed between the complexes formed by estradiol and 4-hydroxytamoxifen but the relevance to opposite biological activities remains unknown.

Activation of the chick oviduct progesterone receptor by heparin in the presence or absence of hormone

Activation (transformation) of the chick oviduct progesterone receptor was found to be induced at 0 degrees C by heparin free in solution as well as by chromatography on a column of heparin linked to acrylamide/agarose. The transformed molecule displayed properties of the activated form of [3H]progesterone-receptor complex obtained by heat treatment or by high ionic strength: smaller size (s20,w = 3.9 S, Stokes radius = 5.2 nm), lower rate of dissociation (t 1/2 approx. 50 h at 0 degrees C compared with approx. 20 h for the 'native' form) and increased binding to phosphocellulose. In all cases, molybdate was an effective inhibitor of transformation and stabilized a large 'native' form (s20,w = 7.9 S, Stokes radius = 7.6 nm). Transformation by neither KCl nor heparin depended on the presence of ligand bound to the receptor, and the properties of the receptor molecule produced by treatment of ligand-free receptor with high ionic strength or with heparin were identical with those of the activated progesterone-receptor complex, demonstrating that receptor activation can be obtained experimentally in the absence of hormone. Our data are compatible with a model in which activation implies separation of the 4 S units, which compose the approx. 8 S 'native' form.

Cytoplasmic progesterone and estradiol receptors in normal, hyperplastic, and carcinomatous endometria: therapeutic implications

This study was designed to determine whether the presence of progesterone receptors (PR) and/or estradiol receptors (ER) could be used to predict progestin responsiveness of recurrent or advanced endometrial cancers. We have demonstrated the presence of physicochemically similar cytoplasmic progesterone and estradiol receptors in normal, hyperplastic, and carcinomatous endometria. All normal endometria contained both PR and ER. Seventy-three percent of endometrial hyperplasias were PR(+) and 93% were ER(+). A decreasing concentration of progesterone receptor activity was observed with increasing tumor anaplasia [grade 1, 84% PR(+); grade 2, 55% PR(+); grade 3, 22% PR(+)] and in irradiated tumors. A statistically significant (p less than 0.001) relationship has been demonstrated between the presence of specific cytoplasmic PR and response to progestin therapy in recurrent or advanced endometrial adenocarcinomas. Thus, we conclude that a PR assay may be used to help select the most appropriate therapy for patients with recurrent or advanced endometrial adenocarcinoma.

Glucocorticoid binding in the hen oviduct

[(3)H]Triamcinolone acetonide (15nm) was incubated with cytosol (150000g fraction) prepared from oviducts of egg-laying hens. The extent of steroid binding, as determined by charcoal assays, was greatest between 2-4h at 4 degrees C. A similar time curve was obtained when cytosol preparations were first fractionated with (NH(4))(2)SO(4) before labelling. The addition of 10mm-Na(2)MoO(4) or 10mm-ATP during the incubation of hen oviduct cytosol with [(3)H]triamcinolone acetonide lowered the extent of steroid binding. The presence of glycerol (20%), however, increased the extent of [(3)H]triamcinolone acetonide binding in cytosol fractions from chick (330%) and hen (160%) oviducts. The [(3)H]triamcinolone acetonide-receptor complex was stable for over 4h at 4 degrees C, but dissociated rapidly at 37 degrees C, exhibiting a half-life of about 10min. The presence of 10mm-Na(2)MoO(4) and 10mm-ATP or both had a small protective effect on the dissociation of [(3)H]triamcinolone acetonide-receptor complex. The receptor from hen oviduct showed significant affinity for unlabelled triamcinolone acetonide, cortisol, compound R5020 and dihydrotestosterone and, to a lesser extent, for oestradiol, oestrone and progesterone. Diethylstilboestrol treatment of immature chicks appeared to induce a more specific binder, which showed affinity for unlabelled triamcinolone acetonide, cortisol and compound R5020 only. Scatchard analysis of [(3)H]triamcinolone acetonide binding in hen oviduct cytosol revealed a K(d) value of 6.4nm. The steroid-receptor complex sedimented as a 7-8S and a 4S entity on low-salt (0.01m-KCl)- and high-salt (0.3m-KCl)-containing sucrose gradients respectively. The cytosol [(3)H]triamcinolone acetonide-receptor complex showed no affinity for ATP-Sepharose or DNA-cellulose, but acquired this ability on heat activation (23 degrees C, 40min). The data indicate the avian oviduct possesses a high-affinity binding molecule that fulfils the criteria of a glucocorticoid receptor.

Progesterone receptors: saturation analysis by a solid phase hydroxylapatite adsorption technique

An assay for cytoplasmic progesterone receptor is described in which receptor is bound to hydroxylapatite and is washed before saturation analysis. Using 3H-progesterone as ligand, the assay yields lower, more reproducible nonspecific binding than is obtained with dextran-coated charcoal techniques and may provide a clinically useful method of measuring progesterone receptor in breast carcinoma. Nuclear progesterone receptors can also be determined by the same technique.

Temperature dependence of kinetic interactions between progesterone and the uterine cytoplasmic receptor

The temperature dependence of the rates of dissociation and association for progesterone-receptor interactions was measured over the temperature range of 0-20 degrees C. The dissociation process is biphasic indicating that either two forms of receptor are present or that the binding of progesterone to the receptor is a concatenated reaction. The enthalpy of activation for the dissociation of progesterone from the receptor is about 26-28 kcal/mol and the entropic energy of activation is about -5 kcal/mol. The enthalpy of activation for the association of these molecules is about 3 kcal/mol and the entropic energy of activation is about 6 kcal/mol. These data are consistent with a model of progesterone binding to the receptor that includes hydrogen bonds between each of the two ketone groups and hydrogen donors on the receptor protein and involves van der Waals' interactions, due to the close proximity of the receptor binding site to a large fraction of the progesterone surface.

Progestin receptors in human uterine cytosol

Progestin(norethindrone and norethindrone acetate)-binding protein, exhibiting characteristics similar to uterine progesterone receptor, has been identified in human uterine cytosol. The progestin receptor was characterized by sedimentation coefficient, 4.2 S; Stokes radius, 39 A; frictional ratio, 1.29; isoelectric pH, 4.6; molecular radius, 2.7 nm; and molecular weight in the range 67 000--74 000. The ammonium-sulfate-precipitated progestin-receptor complex was eluted from a DEAE-cellulose column at 0.18 M KCl. The progestin binding was saturable and stereospecific. The sequential variation in receptor concentration (early proliferative, 3800--4300 sites/cell; late proliferative, 9500--11 200 sites/cell; early secretory, 4900--6200 sites/cell; late secretory, 1800--2300 sites/cell) was in conformity for progesterone and the progestins, when concurrently measured. Oral administration of norethindrone significantly reduced the cytoplasmic and nuclear receptor concentration for estradiol and progesterone. A significant observation was that the progestins stabilized the receptor by forming a slowly dissociating complex with a t 1/2 approximately 110--130 min as compared with the progesterone-receptor complex dissociating with t 1/2 approximately 41 min. Thus, the uterine progestin receptor recognizes progestins in general, although with a varying degree of affinity, and the altered rate constants could be of putative importance in determining the biological potency of the progestins.

Assay of nuclear estradiol receptor by exchange on glass fiber filters

A glass fiber filter exchange assay for nuclear estradiol receptor in human endometrium has been developed. It permits both exchange and measurement of bound radioactivity to be performed without any transfer of the nuclear preparations. Suspensions of nuclei containing estradiol-receptor complexes are adsorbed onto glass fiber filters. Receptor sites, both empty and occupied by endogenous hormone, are labelled by incubation with 20 nM [3H]estradiol without (total binding) or with 2 microM radioinert estradiol (nonspecific binding). Buffer containing unbound radioactive estradiol is then drained, the filters washed, transferred into vials and counted in toluene-based scintillator. Following removal from the scintillator, DNA content of the filters can be measured by the Burton procedure. This exchange technique is easy and specific, with accuracy and precision similar to those of the technique of Bayard et al. (Bayard, F., Damilano, S., Robel, P. and Baulieu, E.E. (1978) J.Clin. Endocrinol. Metab. 46, 635-648). It offers the advantage of increased sensitivity, allowing receptor determinations on nuclear samples containing more than 10 microgram DNA. Approximately 20 measurements can be made from 50 mg tissue (wet weight).