Prolonged cultivation of rat uterine cells with preserved estrogen responsiveness

A rat uterine cell culture was prepared as an experimental system for investigation of mechanisms of steroid hormone actions. Cells frequently supplemented with fresh medium were successfully cultured for 4 weeks through 2 successive passages. Studies of estrogen responsiveness in the primary culture as well as in it's first subculture were performed by a small scale uptake assay for determination of specific steroid binding. Scatchard analysis of specific ovarian hormone binding confirmed that cultured uterine cells preserve both estradiol and progesterone receptors. Characteristics of specific [3H]estradiol binding detected in cells of the first subculture were comparable to those obtained in the initial primary culture. The number of specific estradiol binding sites was diminished to one third of the initial values only in cells of the second subculture, 22 days after isolation of cells from tissue. In the primary culture and in it's first subculture the cells responded to estradiol with a 2-3-fold increase in progesterone receptor level. The subcellular distribution of steroid receptors was also studied; estradiol receptor complexes were detected predominantly in the nuclei whereas progesterone receptors were nearly equally distributed between nuclei and cytosol.     

Characteristics of the nuclear translocation of progesterone receptor in fetal guinea pig uterus "in vivo", "in vitro" and in organ culture

The translocation of progesterone receptor from the cytosol into the nucleus was studied under "in vivo" and "in vitro" conditions in the uteri of guinea pig fetuses exposed to progesterone or a synthetic progestin, R5020. Progesterone treatment of estrogen-primed fetuses leads to a rapid (before 1h) transfer of cytosol progesterone receptor into the nucleus which is, however, short-lived (less than 3h). A rapid decrease in the retention of the estrogen receptor in the nucleus also occurs. In the "in vitro" incubations of whole fetal uteri, translocation of progesterone receptor is temperature-dependent and specific for progesterone and R5020; estradiol and cortisol have no effect. Putative progesterone receptors can also be induced in explants of fetal guinea pig uteri in organ culture which translocate from the cytosol into the nucleus under the same "in vitro" conditions as in whole uteri. Fetal uterine progesterone receptor, either stimulated "in vivo" by estrogen-priming or induced in organ culture, translocates from the cytosol into the nucleus and this process seems to be accompanied by a decrease in retention of the estrogen receptor in the nucleus which appears to be the mechanism by which progesterone antagonises estrogen action in fetal guinea pig uterus.     

Estrogen and progesterone receptors in mammary tumors induced in rats by simultaneous administration of 17ß-estradiol and progesterone

Mammary tumors were promoted in male rats of the Wistar WAG strain by continuous and simultaneous administration of 17ß-estradiol and progesterone. Tumor induction and growth were dependent on estradiol and on progesterone. Their histological features were comparable with those of human breast cancers. Hormone receptors were present in tumor cells. Estradiol receptor was found in 95% of them, at a higher level in nuclei than in cytosol. Progesterone receptor was present in 75% of tumors. In all cases, the level of androgen receptor was low.     

Evidence for a Leydig cell progesterone receptor in the rat

Tritiated promegestone [3H] R 5020 is bound with high affinity by charcoal-treated cytosol prepared from purified Leydig cells. The binding is characterized by high affinity (Kd = 2 x 10(-9) M) and specificity (R 5020 = progesterone greater than testosterone = dehydrotestosterone greater than hydroxyprogesterone greater than cortisol = dexamethasone greater than estradiol) appropriate for progesterone receptors. In vitro, progestin-bound cytosol was quantitatively translocated to nuclei fractions, only if cytosol samples were previously labeled at 25 degrees C. However no translocation of binding activity was observed when previous cytosol labeling was done in the presence of sodium molybdate. Effects of glucocorticoids, androgens and estrogens on the Leydig cell are well documented, the demonstration of a putative progesterone receptor raises the possibility of direct effect of progesterone on the Leydig cell.     

Characterization and physiological variation of estrogen receptors in rabbit corpora lutea throughout pregnancy and pseudopregnancy: the effect of hysterectomy and sustained estradiol treatment

Previous studies suggest that regression of the rabbit corpus luteum is associated with a uterine-induced loss of responsiveness to estradiol. To determine if this is due to loss of estrogen receptor, cytoplasmic and nuclear estrogen receptors were measured in pseudopregnant, hysterectomized-pseudopregnant and pregnant rabbits throughout luteal life. Estrogen receptor levels were higher in corpora lutea than in nonluteal tissue and were generally higher in nuclei compared to cytosol. Estrogen receptor levels were low on Day 3, increased 2- to 3-fold by Day 6-8, reached peak levels by Days 8-10, and then gradually decreased in a pattern similar to the pattern of serum progesterone typical of each group. Hysterectomy was not associated with elevated cytoplasmic or nuclear estradiol receptor levels. When hysterectomized rabbits were treated with estradiol-filled Silastic implant on Day 1, nuclear estradiol receptor levels fell by Day 20 to levels seen in untreated hysterectomized rabbits. Despite substantial losses in nuclear estrogen receptor, serum progesterone remained elevated on Days 16 and 20. Thus, the ability of estradiol to maintain serum progesterone in hysterectomized rabbits did not correlate directly with the level of estrogen receptor.     

Translocation of protein kinase C from cytosol into cell membranes after treatment with estradiol and enzyme activation in target cells

The effect of 17 beta-estradiol on protein kinase C in target cells was studied. It was shown that 10-15 min after injection of ovariectomized animals with estradiol (10 micrograms intraperitoneally) protein kinase C is translocated from the cytosol into the cell membranes of estradiol-dependent mammary gland tumours. A similar effect of estradiol on protein kinase C is observed in uterine tissue. On the contrast, in hormone-independent rat mammary gland tumours estradiol causes no redistribution of protein kinase C between the cytosol and cell membranes. No protein kinase C accumulation in the membranes of hormone-dependent mammary gland tumours is observed 30 min after estradiol injection. However, this period is characterized by the appearance of protein kinase whose activity is not stimulated by Ca2+ or phosphatidylserine and which is eluted from DEAE-cellulose with 0.2 M NaCl. This protein kinase presumably corresponds to the M-fragment, i.e., the catalytic part of protein kinase C formed as a result of protein kinase C proteolysis on the membranes. It seems likely that estradiol, similar to growth factor peptides, realizes its stimulating effect on cell division primarily at the expense of coupling of its membrane receptors with the protein kinase C activation system.     

酪氨酸对大鼠子宫胞浆雌,孕激素受体的影响

采用放射受体分析法,测定了动情周期不同阶段及去卵巢大鼠子宫胞浆雌二醇和孕酮受体含量,并观察了子宫腔内注射酪、丝、苏三种氨基酸对子宫胞浆雌。醇、孕酮受体含量的影响。结果表明：（１）Ｌ－酪氨酸对动情前期、动情期、间情期大鼠子宫胞浆雌二醇和孕酮受体都具有明显的降低作用。（２）Ｌ－酪氨酸也降低去卵巢大鼠子宫胞浆雌二醇和孕酮含量,即这一作用不是通过影响卵巢激素分泌实现的。（３）Ｌ－苏氨酸仅可降低动情期和间情期大鼠子宫胞浆孕酮受体含量,而对相应周期雌二醇受体没有明显作用。（４）Ｌ－丝氨酸和Ｌ－苏氨酸对去卵巢大鼠子宫胞浆雌二醇和孕酮受体均无影响。     

Changes in cytosol and nuclear progesterone receptor concentrations in the rabbit uterus and their relation to induction of progesterone-regulated uteroglobin.

To study the relation between steroid receptor concentrations and biological response, we measured cytosol and nuclear progesterone receptors from rabbit uterus under different experimental conditions, and compared receptor values with induction of uteroglobin, a progesterone-regulated protein. A 5-day progesterone treatment (1 mg/kg per day) reduced the nuclear receptor content by 40%, slightly elevated cytosol receptor levels and increased uteroglobin content 3000-fold. Estradiol and tamoxifen altered progesterone-induced changes in the receptor and uteroglobin values: cytosol and nuclear receptors rose significantly, but uteroglobin induction declined markedly, when progesterone treatment was supplemented with estradiol or tamoxifen. A 50% inhibition of progesterone action on uteroglobin synthesis was achieved with 1 μg/kg of estradiol per day. Thus under certain conditions, there is a clear disparity between steroid receptor levels and biological response.     

Glucocorticoid receptors in mouse mammary tumors: Specific binding to nuclear components.

The specific interaction of glucocorticoids with nuclei of mouse mammary tumor was studied in vitro by incubation of the tissue with [3H]dexamethasone at 25 degrees. It was demonstrated that the mammary tumors contain a limited number of specific nuclear binding sites which were saturated with low hormone concentrations (10-8 M)9 The concentrations of specific binding sites in the nuclei were related to the concentration of cytoplasmic binding sites of unincubated tissues and varied between individual tumors. The binding component in the nuclei appeared to be a protein and was easily solubilized with 0.4 M KCl containing buffers. The ability of various corticoids to block the nuclear localization of the steroid correlated well with their glucocorticoid potency. Estradiol and progesterone at concentrations of 10-6 M were also effective in competing for the glucocorticoid receptor binding sites. However, while the glucocorticoids such as hydrocortisone and corticosterone translocated to nuclear sites also specific for dexamethasone, estradiol and progesterone competed for the cytoplasmic binding sites and did not translocate to the nucleus. The possible significance of the interaction of various steroids with the glucocorticoid receptors in mammary tumors is discussed.     

Hypothalamic and hypophysial progesterone receptors: Estrogen-priming effect,differential localization, 5α-dihydroprogesterone binding,and nuclear receptors

Specific progesterone receptor of 7S which can be isolated from rat female hypothalamic and hypophysial cytosols was further investigated in terms of its induction effects by estrogen-priming, intracerebral localization, 5α-dihydroprogesterone (DHP) binding, and nuclear receptors. Estrogen-priming was necessary for the appearance of the cytosol receptors. The 7S hypothalamic and hypophysial receptors were increased in a dose dependent fashion by estradiol injections. The maximal effective doses of estradiol benzoate for both tissues were 1 and 10 μg, respectively.The receptors were mostly localized in the median eminence, preoptic-anterior hypothalamus and anterior hypophysis of estrogen-primed immature and mature rats, but little or no 7S binding was detected in the cerebral cortex, reticular formation, amygdaloid complex and posterior hypophysis. This differential localization of progesterone receptors resembles that of estrogen receptors, suggesting possible induction of progesterone receptors in these specific brain regions by estrogen.Progesterone receptor complexes of 5S were isolated from “purified” nuclei of anterior pituitaries from estrogen-primed adult female rats. These results on the cytosol and nuclear receptors suggest that progesterone can directly act on the brain through its interaction with specific progesterone receptors in the hypothalamus and hypophysis. It is noteworthy that 5α-DHP can bind the progesterone receptors in both tissues, suggesting its direct feedback action on the brain through the receptors.     

Binding of progesterone receptor by nuclear preparations of rabbit and guinea pig uterus.

Guinea pig and rabbit uterine nuclei bound [3H] progesterone in vitro only in the presence of cytosol from estrogen-stimulated uteri. Nuclei from unstimulated and estrogen-stimulated uteri bound progesterone equally well. Nuclei of nontarget tissues also bound progesterone, but to a lesser extent. The rate of nuclear bindins increased with temperature from 0-30 degrees. At 25 degrees nuclear binding remained stable for at least 3 h, but at temperatures of 30 degrees and greater, nuclear binding decreased rapidly after 15 min. Activation of the progesterone-cytoplasmic receptor complex (the change in the complex that enables it to bind quickly to nuclei at 0 degrees) took place slowly at temperatures from 0-5 degrees and rapidly at 10-25 degrees. Activation was facilitated by dilution of the cytosol. Some activation occurred in diluted cytosol in the absence of added progesterone. The cytoplasmic progesterone receptor had a sedimentation coefficient of 7 S when concentrated cytosol (20 mg of protein/ml) was incubated with progesterone at 0 degrees in 5 mM phosphate buffer. Diluting the cytosol and increasing the temperature to 20 degrees caused the sedimentation coefficient to decrease to 5.5 S. Gel filtration of guinea pig uterine cytosol on Sephadex G-100, in the absence of progesterone, yielded a progesterone-binding fraction in the void volume, with a sedimentation coefficient of 5.5 S. The complex of progesterone with the material in the void volume was taken up by nuclei at 0 degrees more rapidly than the complex of progesterone and crude cytosol. The nuclear uptake of progesterone was decreased in phosphate buffer of concentrations greater than 80 mM. Under conditions that favor the nuclear binding of progesterone, the sedimentation coefficient of the cytoplasmic progesterone receptor was 5.5 S. This may be the form of the preceptor which is taken up by nuclei. In decreasing order of effectiveness, unlabeled progesterone, 5 alpha-pregnane-3,20-dione, corticosterone 20 alpha-hydroxy-4-pregnen-3-one, testosterone, estradiol-17 beta, and cortisol competed with [3H] progesterone for binding to nuclei.     

Progesterone regulation of estrogen receptor in the rat uterus: A primary inhibitory influence on the nuclear fraction

The purpose of this study was to determine the short-term effects of progesterone action on estrogen receptor (Re) levels in the rat uterus. Ovariectomized, adrenalectomized rats were maintained on subcutaneous Silastic implants containing crystalline estradiol. Progesterone treatment with serum estradiol maintenance caused a rapid decrease (within 4 h) of total Re, attributable to loss of nuclear Re without a significant change in cytosol Re levels. Removal of estradiol implants resulted in an increase in total Re and cytosol Re at all time periods studied without a significant decrease in nuclear Re until 8 h. Combined estradiol withdrawal and progesterone treatment resulted in lower total Re levels and a more rapid decrease in nuclear Re than with estradiol withdrawal alone. These results demonstrate that progesterone rapidly and selectively decreases nuclear Re levels in rat uterus and suggest that this process is not dependent on cytosol Re or serum estradiol levels.     

Hormonal regulation of estrogen and progestin receptors in decidual cells

Total estrogen receptor (Re) and total progestin receptor (Rp) were measured in the cytosol and nuclear fractions from hamster deciduomal tissue and decidual cell cultures. Correlation of serum steroid (estradiol and progesterone) and deciduomal receptor profiles revealed a significant loss of Re during the first four days of decidualization that was not attributable to changes in serum steroid levels. A decidual cell-tissue culture system was used to study the receptor's recovery response to progesterone withdrawal. Decidual cells were plated and grown in Ham's F12/Dulbecco's modified Eagle's medium with 5% horse serum supplemented with insulin, transferrin, selenium and progesterone (10 ng/ml). Within 48 h of culture large, multinucleate decidual cells were observed by phase microscopy. At 72 h of culture in medium containing progesterone, only Rp was detectable in decidual cells. Re was not detectable (less than 200 fmol/mg DNA) in either cytosol or nuclei from cells maintained in the presence of progesterone. However, when progesterone was deleted from the medium, cytosol Re recovered progressively from 8 h to 16 h of culture. Progesterone withdrawal also caused parallel increases in cytosol and nuclear Rp, and estradiol treatment (2 ng/ml) in combination with progesterone withdrawal further enhanced Rp levels in decidual cell cultures. These results with cultured decidual cells demonstrate that progesterone down-regulates Re and Rp, Re recovers rapidly upon progesterone withdrawal, and the Re system is competent to respond to estrogen action in terms of Rp induction. We used the density-shift method to determine that progestin increases the turnover of nuclear Re in hamster decidual cells within 3 h. Hamster decidual cells were isolated from the endometrium and cultured in progesterone-free medium containing normal amino acids (1H, 12C, 14N) for 2 days. Confluent monolayers of cells were exposed to 1 nM estradiol (E2) for 1 h to maximize the amount of occupied Re in the nuclear fraction. Then, at time 0, cells were transferred to medium supplemented with dense (2H, 13C, 15N) amino acids and either 1 nM E2 or E2 plus 100 nM progesterone. After Re was labeled with dense amino acids for 1, 3, 6 and 9 h, nuclear Re was extracted with 10 mM pyridoxal -5' phosphate and labeled with 125I-iodoestradiol (5 nM). Two radioactive peaks representing preexisting and newly synthesized Re were separated by sucrose density-gradient centrifugation. The halflife of nuclear Re in decidual cells was 3.7 h when cells were treated with E2 alone.(ABSTRACT TRUNCATED AT 400 WORDS)     

The effect of estradiol on the activity of cAMP-dependent protein kinase in cells of estradiol-dependent tumors of the rat mammary gland. The role of a thermally stable protein inhibitor of cAMP-dependent protein kinase

Stimulation of rat mammary tumour growth by estradiol is due to the activation of the adenylate cyclase system and cAMP-dependent protein kinases. A single administration of estradiol to ovariectomized rats causes a rise in the cAMP-dependent protein kinase activity in cell nuclei within the first 4-6 hours after injection. This effect is probably due to the translocation of enzymes into nuclei and an increase of their synthesis. The high level of the cAMP-dependent protein kinase activity in cell nuclei was observed in actively growing intact mammary tumours, in contrast to regressing ones in ovariectomized animals. This phenomenon can be accounted for by the decrease in the content of a thermostable protein inhibitor of cAMP-dependent protein kinases rather than by the high level of cAMP.     

Activation of tyrosine kinases during induction of mammary gland tumors in GR mice by ovarian hormones

In GR mice, the induction of proliferative processes in mammary tumours with ovarian hormones (estrone and progesterone) is accompanied by the activation of phosphorylation of plasma membrane, cytosolic and nuclear proteins by endogenous protein kinases. The hormones stimulate tyrosine kinases of tumour cells whose activity is as high as 14.9-17.9% of the total phosphorylation in plasma membranes and 9.5-10.4% in cell nuclei. The ovarian hormones stimulate tyrosine kinases of tumour cells which phosphorylate proteins with Mr of 110-230 and 15 kD (plasma membranes), 170, 52 and 13 kD (cytosol) and 32 kD (nuclei) which are resistant to alkaline hydrolysis. Apart from tyrosine kinases, the ovarian hormones also stimulate serine and threonine protein kinases which seems to be due to the activation of protein kinase C and other protein kinases.     

Sensitivity of progesterone receptors to aurintricarboxylic acid: Inhibition of nuclear uptake,ATP and DNA binding

When hen oviduct cytosol samples containing progesterone receptor complexed to [³H]progesterone were included with isolated nuclei in presence of 0.2 mM aurintricarboxylic acid, more than 50% inhibition occurred in the uptake of progesterone receptor by the nuclei. The activated form of progesterone receptor appeared to be more sensitive to the presence of aurintricarboxylic acid since pretreatment of non-activated progesterone receptor with the inhibitor and the subsequent removal of the latter prior to activation did not result in the inhibition of receptor uptake by the nuclei. Also, the binding of progesterone receptor to columns of DNA-cellulose or ATP-Sepharose was abolished under simmilar conditions. When nuclei, ATP-Sepharose or DNA-cellulose were preincubated with the inhibitor prior to the addition of receptor preparations, no such inhibition resulted indicating that the inhibitor may be interacting with the receptor protein and not complexing to ATP, DNA or sites in the nuclei. The steroid binding properties of progesterone receptor, however, remained intact under these conditions. Both A and B forms of progesterone receptor are equally sensitive to aurintricarboxylic acid presence when tested for their nuclear uptake. Aurintricarboxylic acid was also found to be very effective at low concentrations (0.25 mM) in eluting the receptor complexes off ATP-Sepharose columns without disrupting the steroid binding properties of progesterone receptor. Our results suggest that auintricarboxylic acid is an effective inhibitor of progesterone receptor and that it may be acting by interfering with a site(s) on progesterone receptor which may be exposed upon activation and are involved in such processes as ATP binding, nuclear uptake and DNA binding. These observations suggest the use of aurintricarboxylic acid as a chemical probe for the analysis of progesterone receptor.     

Significance of lipoidal estradiol in human mammary tumors

Incubations of p-nitrophenyl fatty acyl esters and estradiol-17 beta fatty acyl 17-esters with porcine esterase, human mammary tumor cytosol and rat uterine cytosol leads to ester hydrolysis of compounds with short chain fatty acids. Esters with long chain fatty acids show no hydrolysis except in the presence of Tween 80. Short chain fatty acid esters have a higher binding potency to the estrogen receptor than long chain fatty acid esters. Extraction of the nuclear receptor peak sedimenting at 4.6S and identification of the steroid showed that about 90% of the radioactivity was associated with estradiol and only 10% with estradiol esters. These studies show that estradiol fatty acyl esters act as a storage form from which estradiol is released by enzymatic hydrolysis.     

Physiologic role of relaxin on mammary gland growth in rats

The role of relaxin in stimulating growth of the mammary gland was assessed in ovariectomized and intact male rats for a period of 20 days. In addition to relaxin alone, the ovarian mammogenic hormones estradiol and progesterone were used in combination with relaxin and with each other to evaluate responses of mammae. Indices for mammary growth included wet weight, dry fat-free tissue, DNA, RNA, total protein, and collagen. Quantitative estimates of DNA and collagen represented the best indicators of parenchymal and stromal growth, respectively. Because changes in body weights were significantly different among hormonally administered groups, these were included as well. In Ovariectomized young rats, relaxin alone and in combination with estradiol and progesterone increased all indices significantly (P less than 0.01). The collagenous portion of total protein was high for the group receiving relaxin alone (62%) compared with the control group (46%). Relaxin administered along with estradiol and progesterone increased collagen accumulation to 73%, compared with 54% in the estradiol + progesterone group. Relaxin did not significantly increase growth indices when administered to male rats at 10 and 20 micrograms/day, while 30 micrograms stimulated a significant increase in total protein (P less than 0.05), suggesting that 30 micrograms of relaxin/day may be considered the basal concentration needed to induce a physiologic response in males. Relaxin induced a growth effect on mammae by synergizing with progesterone and estradiol in order to stimulate parenchymal proliferation, as noted by a DNA increase, and to increase stromal distensibility of the mammary pad by invoking accumulation of collagen and total protein in substituting for mammary adipose tissue.