Mechanism of action of the sex steroid hormones (third of three parts)

Estrogen receptors in the adrenal cortex of the possum (Trichosurus vulpecula)

1. Specific [3H]estradiol binding activity with characteristics of estrogen receptors was found in the cytosols and nuclear extracts of the adrenal cortex proper and special zone of the brushtail possum (Trichosurus vulpecula). 2. The specific estradiol receptor had a sedimentation coefficient on sucrose gradients of approximately 9S and a molecular weight on gel filtration of more than 200,000. The adrenal cortex cytosol binds [3H]estradiol with high affinity (Ka 5.5 X 10(9) M-1), and limited capacity (Bmax 62.7 fmol/mg cytosol prot). In competition experiments with different steroids the receptor showed a high affinity for four estrogens and a very low affinity to androgens, progesterone and cortisol. 3. There was no difference in the affinity and maximum binding capacity of the cytosols from cortex proper in male and female animals, but the binding capacity of the special zone of females was half that of cortex proper. Estradiol receptors were found in the kidney, liver, lung, testis and muscle but only in the adrenal and prostate was the binding capacity relatively high compared with the uterus. 4. The specific binding capacity of [3H]estradiol to cytosols of adrenal cortex at different stages of the estrus cycle and pregnancy was unrelated to that of the uterus. In the adrenal the receptor concentration was lowest at estrus, when uterine concentration was high, while in late pregnancy the binding of adrenal cortex and uterus cytosols was almost the same. 5. The possible physiological significance of the presence of a specific estrogen receptor in male and female possums is discussed.

Biochemical effects of 17 beta-estradiol on UMR106 cells

The effect of 17 beta-estradiol (E) on an osteoblast-like cell line, UMR106, was studied in vitro. The concentrations of transferrin and seven enzymes (gamma glutamyl transferase, alkaline phosphatase, acid phosphatase, lactate dehydrogenase, creatine kinase, alanine aminotransferase and aspartate aminotransferase) were measured in these cells after incubation in culture medium containing either E or the vehicle. E treatment increased five of the seven enzymes and increased the transferrin concentration in the UMR106 cells while simultaneously reducing the proliferation rates. 4-Hydroxytamoxifen, an estrogen antagonist, produced a mild estrogen agonist action on growth rates and enzyme concentrations in the UMR106 cells. When E was present simultaneously, the agonist properties of 4-hydroxytamoxifen were enhanced. These studies show that E enhanced activity of five enzymes and the transferrin content of UMR106 cells after a 2-day incubation. 4-Hydroxytamoxifen enhanced the E effect, illustrating that estrogen antagonists may manifest agonist or antagonist properties depending on the model. These results extend our previous observations showing a direct effect of E in vitro on osteoblast-like cells.

Hypogonadism in liver cirrhosis: implication in altered amino acid metabolism in muscle

To investigate the relationship between hypogonadism and altered amino acid metabolism in patients with liver cirrhosis, we measured the basal levels of plasma testosterone, estradiol, and free amino acids, plus urinary 3-methylhistidine excretion, in 16 control and 19 cirrhotic patients. The concentration of plasma testosterone correlated significantly with that of plasma branched-chain amino acids, and inversely with urinary 3-methylhistidine excretion. This suggests that hypogonadism causes a disturbance in amino acid metabolism at least partly related to an augmented muscle protein turnover.

Oestradiol and progesterone receptors in the pig oviduct during the oestrous cycle

The concentrations of the tissue receptors for oestradiol (E) and progesterone (P) in the porcine oviduct at different stages on the oestrous cycle have been investigated by in vitro binding and exchange methods. Both hormones bound to specific cytoplasmic (Rc) and nuclear (Rn) receptor proteins with high affinity. The concentrations of ERc and ERn were two-fold higher in the ampulla as compared to the isthmus. The amount of ERc in the isthmic portion of the oviduct did not vary throughout the oestrous cycle. However, the ampullar ERc concentrations increased during prooestrus, showed a maximum at standing oestrus, thereafter decreasing. Significant variations in the amount of oviductal ERn were observed. Despite the differences in ERn amounts between segments, the concentration of ERn increased significantly during late prooestrus, attaining a three-fold elevation and remaining elevated during the period of standing oestrous and early luteal phase (days 3-4), thereafter returning to basal levels. No significant variations in the amount of isthmic PRc were found throughout the period studied. The ampulla, however, showed a significant increase in PRc concentrations during standing oestrus, thereafter decreasing. The concentrations of PRn in isthmus and ampulla were of about the same magnitude and varied significantly during the oestrous cycle, increasing in concentration from standing oestrous onwards. The temporal relationships between the variations in levels of oestradiol and progesterone receptors in oviductal tissues and those of the circulating plasma levels were established. The data obtained in this study suggest a relationship between the changes in the levels of oestradiol and progesterone oviductal binding during the first days of the oestrous cycle, and the gamete and embryo transport throughout the oviduct in the porcine species.

Axonal projections and peptide content of steroid hormone concentrating neurons

The axonal projections of cell groups containing the most dense collections of steroid hormone concentrating cells have been demonstrated with retrograde neuroanatomical tracing methods. Horseradish peroxidase revealed large numbers of neurons in ventrolateral ventromedial nucleus (VL-VM) which project to dorsal midbrain. Wheat germ agglutinin (immunocytochemical recognition method) revealed large numbers of neurons in medial basal hypothalamus (MBH) and particular subdivisions of paraventricular nucleus (PVN) that project to dorsal caudal medulla or spinal cord. Fluorescent dyes revealed that many preoptic area (POA), anterior hypothalamic (AHA), and bed nucleus of the stria terminalis (BNST) neurons project to ventral tegmental area of Tsai (VTA). Also many neurons in POA and BNST project to amygdala. A method which enabled simultaneous demonstration of the steroid binding capacity and axonal projections of neurons in the same tissue section revealed that 26-36% estradiol (E2) concentrating cells in VL-VM project to dorsal midbrain. E2 concentrating neurons in POA and BNST project to amygdala and E2 concentrating POA neurons project to VTA. These neurons, which send their axons to cell groups located in different brain regions, are probably under the genomic-regulatory influence of E2. Using a method which allows simultaneous demonstration of peptide content and steroid hormone concentrating capacity of cells, many oxytocin-neurophysin and vasopressin-neurophysin containing magnocellular neurons in the caudal PVN were found to concentrate E2. About 4% of the beta-endorphin and about 6% of the dynorphin containing neurons in the MBH concentrate E2. In contrast, virtually none (less than 0.2%) of the LHRH containing hypothalamic neurons concentrate E2.

Binding of progestins to the glucocorticoid receptor. Correlation to their glucocorticoid-like effects on in vitro functions of human mononuclear leukocytes

A number of physiological and synthetic progestins were tested for their ability to compete with [3H]dexamethasone for the binding to the glucocorticoid receptor of human mononuclear leukocytes and their ability to elicit glucocorticoid-like effects on the same cells. As compared to the reference compound dexamethasone (relative receptor binding affinity defined as 100%), two potent synthetic progestins with a pregnane-type structure, megestrol acetate and medroxyprogesterone acetate, were found to display a considerable binding affinity towards the receptor (46 and 42%, respectively). The relative binding affinity of the naturally occurring ligand, cortisol, to the receptor was clearly lower (25%). The effective binding of medroxyprogesterone acetate to the glucocorticoid receptor was confirmed by direct binding studies utilizing a tritiated derivative of this steroid. No evidence for the existence of a specific progesterone receptor in human mononuclear leukocytes was obtained as judged by the results of competition experiments where a progesterone receptor-specific ligand [3H]Org 2058 was used. Medroxyprogesterone acetate and megestrol acetate also induced glucocorticoid-like effects on the lymphocyte functions. These included inhibition of the proliferative responses to the T-cell mitogens concanavalin A and phytohaemagglutinin and an enhanced accumulation of immunoglobulin secreting cells in pokeweed mitogen-stimulated cultures. The progestin effect appears to be mediated through a radiosensitive (suppressor) subpopulation of T lymphocytes. In contrast, the synthetic progestins related structurally to 19-nortestosterone, norethisterone and d-norgestrel, were virtually devoid of binding affinity towards the glucocorticoid receptor nor did they measurably influence the in vitro lymphocyte functions. These studies demonstrate that certain progestins in common clinical use probably possess inherent glucocorticoid activity and suggest that side effects attributable to this character (e.g. suppression of the pituitary-adrenal axis) might be expected when these compounds are used in pharmacological doses.

Gestational carcinoma of the female breast

Few neoplastic diseases can equal the amazing complexity and sheer perversity of carcinoma of the breast. No doubt as many decades of research lie ahead in its study as already have passed. Clinicians have long appreciated the special relationship of the disease to gestation. Diagnosis and treatment of breast cancer during pregnancy represent only a small part of this fascinating relationship. Although indispensable as research tools, animal models pertain to the human disease only in limited, ill-defined ways. The etiology of human breast cancer remains unclear; chemical, viral, hormonal, genetic, and immunologic theories have all been put forward as possibilities. Although gestation clearly alters both the initiation and growth of mammary tumors, its exact role in the various theoretical considerations remains a mystery. The obstetrician-gynecologist holds an important front-line position in the war against breast cancer, as does any provider of primary care to women, and, indeed, as do women themselves. Rather than decrease vigilance during pregnancy, the physician should pursue with extra vigor any breast mass discovered in the gravid patient, when the clinical examination is even less reliable than usual. The finding of a breast mass usually necessitates biopsy. Except for the inclusion of specific pregnancy-related problems, such as galactocele, the diagnostic spectrum of breast masses removed during pregnancy does not differ from that in nonpregnant women. The discovery of a highly suspicious breast mass, or the confirmed biopsy diagnosis of malignancy, in a pregnant patient should indicate the need for referral to a surgical oncologist versed in this unusual problem. The best approach to gestational breast cancer continues to be the team approach, with consultation from specialists in obstetrics, surgical oncology, anesthesiology, nuclear medicine, radiology, radiation oncology, pathology, and medical oncology. The age and general condition of the patient, the extent of the tumor, the stage of gestation, and the informed opinions of the patient and her spouse help to determine the therapeutic strategy. Careful staging not only guides present therapy but also the therapy of future victims through continued investigation. Most surgeons favor operation without delay if cure seems within reach. Mastectomy, with or without cesarean section, can be accomplished without detriment in the hands of a knowledgeable surgeon-anesthesiologist team. By following certain guidelines, the search for metastasis can be conducted safely and appropriately. The clinical situation occasionally may require the initiation of adjuvant radiotherapy or chemotherapy during pregnancy, by experienced consultants. Ongoing studies of tissue hormone receptors and cell kinetics will continue to give insight into the effects of gestational hormones on breast cancer and can aid in the selection of treatment options for the individual patient...

Deficiency of androgen receptors in male pseudohermaphroditism

A diagnosis of androgen receptor deficiency was made in a male with ambiguous genitalia during the neonatal period. Since the neonate had a small hypospadiac phallus with laboratory evidence of a receptor deficiency and clinical unresponsiveness to high levels of androgen, it was decided to assign a female gender. Bilateral orchiectomy and phallic recession were performed.

Effect of androgen on the transcription of rat prostatic binding protein genes

The mechanisms whereby androgens modulate mRNA levels for the C1, C2 and C3 prostatic binding protein genes in the rat ventral prostate have been investigated. Transcription rates for the 3 genes were lowered 2-3-fold upon castration but found to increase again upon re-administration of testosterone. Although this demonstrated a direct effect of androgens at the transcriptional level for these genes, the rates of mRNA synthesis were insufficient to account for previously observed steady-state measurements. This was confirmed by analysis of the nuclear steady-state levels for each mRNA following hormonal manipulation of the rats in vivo. It is concluded that besides direct transcriptional regulation, androgens must also exert a major effect of the half-life of these mRNAs in the rat ventral prostate.

Some theoretical questions of the peptide and steroid hormone regulation. Part I.: The receptor-steroid variable complex (RSVC) hypothesis of genetic regulation

Steroids exert their known biological and biochemical effects in connection with specific receptors. These effects are so various and complex that it is impossible to explain them on the basis of a concept supposing the presence of only one unique receptor molecule in the target organs. The heterogeneity in the function of steroids requires a heterogeneity in the molecular composition of the receptor-steroid complexes. Direct and indirect evidence is presented to support a multiplex, heterogene receptor theory. The possible origin of this complexity is analyzed and a new concept of specific gene regulation by heterogene receptor-steroid complexes is suggested. in this theory the distribution and sequence of one or more steroids on the receptor can carry and serve highly specific and unique information capable or recognizing and binding to the acceptor site of the chromatin and regulating gene expressions specific for steroids. The formation of such Receptor-Steroid Variable Complexes (RSVC) has been mathematically analyzed and the properties of a chromatin protein capable of detecting both the DNA and the steroid sequences on the receptor are discussed.

Estrogen and progestin receptors in endometriosis lesions: comparison with endometrial tissue

Cytosol estrogen (ER) and progestin (PR) receptors were quantified in 47 endometriosis lesions from 41 patients and compared with receptor measurements in the endometrial tissue of nine of these patients. Half of the specimens of endometriosis tissue contained PR only, in concentrations that were significantly lower than in the endometrium. Only 30% of the specimens of endometriosis tissue contained the two receptors simultaneously, and levels of ER were very low compared with those in the endometrium. Levels of PR in the specimens of endometriosis tissue were highest at the periovulatory period, whereas concentrations of ER tended to be highest at the beginning and close to the end of the cycle. These results suggest that regulation of these receptors is dissimilar in endometriosis lesions and endometrium. It remains to be seen whether differences in receptor distribution in the lesions of individual patients could explain differences in the course of this disease, and have therapeutic implications. The presence of PR in the majority of the endometriosis lesions is in accord with the favorable therapeutic response often obtained with progestin treatment of this disease.

Binding of the cytotoxic and antitumor triterpenes, cucurbitacins, to glucocorticoid receptors of HeLa cells

1. The binding of cucurbitacins to glucocorticoid receptors in HeLa cell-free systems and in intact cells was studied by competition with [3H]cortisol. Cucurbitacins were found to diminish the [3H]cortisol binding. 2. The difference in binding affinity at two temperatures suggest that cucurbitacins are metabolized under physiological conditions. 3. A linear correlation was observed between logarithms of relative binding affinities and of cytotoxic activities of cucurbitacins. Hence, the cucurbitacin binding to glucocorticoid receptors seems to be a necessary step for cytotoxic action of these compounds. 4. Cucurbitacin I was found to form cytoplasmic and nuclear salt-extractable complexes with glucocorticoid receptors of intact HeLa cells at 37 degrees C. Unlike cortisol, cucurbitacin I did not produce salt-resistant nuclear complexes.

The use of medroxyprogesterone acetate for relief of climacteric symptoms

Climacteric symptoms in the menopausal woman are perplexing to the physician. Recent literature concerning the relationship of estrogen to carcinogenesis has caused many women to discontinue this medication; thus, there is a need for an alternative therapy for the relief of these symptoms. The drug medroxyprogesterone acetate (Depo-Provera) was assessed in a double-blind, randomized, placebo-controlled study involving 48 subjects. Only one of the placebo-treated patients claimed any relief from climacteric symptoms while only two of the patients who received the study drug noted little or no relief (P < 0.0001). Relief from climacteric symptoms began at 4 to 7 days after entry into the study and extended for 8 to 20 weeks. The only side effects were withdrawal bleeding and a slight, transient weight gain. Depo-Provera appears to be a reliable substitute for estrogen in the treatment of climacteric symptoms. Further investigations with this medication seem indicated.

Endometrial estrogen and progestin receptors in women bearing a progesterone-releasing intrauterine device

Endometrial biopsies were obtained from eleven volunteers bearing a progesterone-releasing intrauterine device (IUD). The mean treatment time was 4.1 yrs (range 1--5 yrs). Tissue samples were collected during the follicular phase of the cycle and assayed for estrogen and progestin receptors with [3H] estradiol and [3H] ORG 2058 (16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione) as the respective radioactive ligands. Both receptor values were significantly lower (p < 0.01) than those present in endometrial tissue of normally menstruating women. The steroid receptor concentrations measured (estrogen receptor 19.6 +/- 9.9 and progestin receptor 134.4 +/- 121/4 fmol/mg cytosol protein) from women with an IUD represented only about 20% of those in endometria of normal women. This result suggests that progesterone released from the IUD has a depressive action on the sex steroid receptor levels which may contribute to the contraceptive effectiveness of the IUD.

Regulation of cytosol and nuclear progesterone receptors in rabbit uterus by estrogen, antiestrogen and progesterone administration

A synthetic progestin, 16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione (ORG 2058), was utilized to measure progesterone receptors from the rabbit uterus. This steroid has a high affinity for both cytosol and nuclear receptors, with KD values of 1.2 nM (at 0--4 degrees C) and 2.3 nM (at 15 degrees C), respectively. Administration of estradiol-17 beta or a non-steroidal antiestrogen, tamoxifen, for 5 days to estrous rabbits led to a progressive rise in the cytosol receptor levels: from 34,000 to 120,000 (estradiol-17 beta) and 80,000 (tamoxifen) receptors/cell, without any major influence on the nuclear receptor content. A single intravenous injection of progesterone (5 mg/kg) elicited a 3-fold increase in the mean nuclear receptor content at 30 min after injection (from 18,000 to 48,000 receptors/nucleus). Nuclear receptor accumulation was short-lived and returned to control levels within 4 h after treatment. A second dose of progesterone given 24 h later doubled the nuclear receptor level (from 18,000 to 35,000 receptors/nucleus). The concomitant decline in the cytosol receptor content was twice that accounted for by the nuclear receptor accumulation (70,000 vs. 30,000, and 40,000 vs. 17,000 receptors/cell, after the first and second progesterone injection, respectively). Following progesterone administration, the cytosol receptor level reached a nadir by 30 min, exhibited minimal replenishment within the ensuing 24 h, and remained at approx. 50% of the pretreatment values. After a single dose or two consecutive doses of progesterone, total uterine progesterone receptor content declined to about 60% of the level prior to each dose, a nadir being reached at 2 h after treatment.

The syndromes of primary hormone resistance

The clinical features, genetics, pathophysiology, and management of endocrine diseases in which primary hormone resistance is the fundamental defect have been reviewed. Primary hormone resistance has been documented for nearly all hormones--vasopressin, parathyroid hormone, growth hormone, adrenocroticotropin, thyrotropin, gonadotropins, insulin, androgens, cortisol, aldosterone, progesterone, thyroid hormones, and vitamin D. A striking exception is estradiol, a steroid that may be vital for early embryonic development. Most of the hormone unresponsiveness syndromes represent only partial defects, and it is likely that most such patients go unrecognized. Therefore, hormone resistance should be suspected not only when a patient presents with hypofunction of particular endocrine system combined with high endogenous hormone levels but also whenever apparently normal function of an endocrine system is associated with inappropriately elevated levels of the corresponding hormone. The value of these defects in hormone responsiveness as a natural laboratory for the study of the normal mechanisms of hormone action is discussed.

Dexamethasone-resistant cystic fibrosis fibroblasts show cross-resistance to sex steroids

Diploid skin fibroblasts derived from individuals with the autosomal recessive disease, cystic fibrosis (CF), were shown previously to be significantly more resistant to the cytotoxicity of dexamethasone, a glucocorticoid hormone, than were normal human fibroblasts. Here cystic fibrosis fibroblasts are also shown to be more resistant than normal human fibroblasts to the cytotoxic effects of the sex hormones, 17 beta-estradiol, dihydrotestosterone and progesterone. Since cells are believed to contain different receptors for each of the steroid hormones, it is not probable than the resistance of CF cells to these hormones results from a receptor deficiency. This was shown by the fact that CF cells were found to exhibit the same receptor activity as normal cells for 3-H-dexamethasone. Furthermore, neither normal human nor CF fibroblasts could be demonstrated to contain detectable receptor activity for 3H-17 beta-estradiol. In addition, the studies of fibroblast killing by hormones led to the further interesting observation that normal human diploid fibroblasts, regardless of the sex of the tissue donor, are sensitive to killing by each of the sex hormones. These findings suggest that the cytotoxic effects of the steroid hormones may be observed independently of the specific hormone receptors. The studies reported here thus suggest that the resistance of CF cells to the different steroid hormones is probably the result of a defect in a pathway in cellular steroid hormone metabolism other than that involving receptors.