Håkan Eriksson

Heterogeneity of estrogen receptors in the cytosol and nuclear fractions of the rat uterus.

Multiple species of estrogen binding sites have been demonstrated in cytosol and nuclear fractions of uteri from immature and adult ovariectomized female rats. Equilibrium binding analyses of uterine cytosol yielded two binding sites, I and II, with dissociation constants of 0.8 and 33 nM respectively. The high affinity cytosol site (0.8 nM - Type I) translocated to the nuclear compartment following estrogen treatment in vivo and appears to represent the classical estrogen receptor which can be measured by 3H-estradiol exchange. Type II sites remain in the cytosol after estrogen injection. A third binding component was observed in the nuclear compartment (nuclear Type II) which binds 3H-estradiol at 4° and displayed cooperative binding characteristics. The presence of these sites in both cytosol and nuclear compartments complicates the accurate measurement and differentiation of these sites. Valid estimates of binding parameters for cytosol Type I and II sites may be obtained by saturation analyses over a wide range of 3H-estradiol concentrations (0.05–40 nM). Nuclear Type I can be differentiated from nuclear Type II by performing saturation analysis under exchange conditions which measure both Type I and II sites and comparing the values obtained when the assay is performed at 4°C which measures only Type II sites.

Formation of pinopodes in human endometrium is associated with the concentrations of progesterone and progesterone receptors

OBJECTIVE To investigate the relation between the development of endometrial pinopodes and the serum concentration of hormones and the distribution of estrogen receptor-alpha, estrogen receptor-beta, progesterone receptor A, and progesterone receptor B. DESIGN Prospective clinical study. SETTING Hospital-based unit of reproductive health and university-affiliated reproductive research laboratories. PATIENT(S) Twenty-seven healthy fertile women with normal menstrual cycles. INTERVENTION(S) Urine and blood sampling for hormone measurement, vaginal ultrasonography, and endometrial biopsy. MAIN OUTCOME MEASURE(S) Appearance of the endometrium on light microscopy, pinopode formation, serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH), and expression of progesterone receptors A and B and estrogen receptors alpha and beta. RESULT(S) Pinopode formation and regression were closely associated with increases and decreases, respectively, in serum progesterone concentration. At pinopode development, levels progesterone receptors A and B in the glandular and luminal epithelial cells decreased; this effect was mainly dependent on the absence of progesterone receptor B. Serum estrogen levels and levels of estrogen receptor alpha and beta did not correlate with pinopode formation. CONCLUSION(S) The increase in serum progesterone level and down-regulation of progesterone receptor B are important in development of pinopodes.

Estrogen regulation of the estrogen receptor and insulinlike growth factor-I in the rat uterus: a potential coupling between effects of estrogen and IGF-I

The interrelationship between estrogen and insulin-like growth factor-I (IGF-I) in the regulation of uterine growth was studied in the rat. The levels of the estrogen receptor (ER), ER mRNA, and IGF-I mRNA in rat uterus and liver were monitored. Uterine ER in normal cycling rats was highest in proestrus and diestrus, as was IGF-I mRNA. ER mRNA and plasma estradiol peaked in proestrus. Hepatic ER mRNA and IGF-I mRNA were highest in diestrus, whereas ER was not significantly changed during the estrous cycle. The temporal effects of multiple injections or continuous infusion of 17 beta-estradiol in ovariectomized rats were examined. In the uterus of animals subjected to multiple injections, a 10-fold increase in IGF-I mRNA was seen 24 h after the start of the treatment, whereas rats given continuous infusion of estradiol showed a more than 16-fold increase. In both groups, the increase of IGF-I mRNA was transient although estrogen treatment was continued. To study local hormonal effects, ovariectomized rats were given estradiol in vaginal implants. The uterine IGF-I mRNA level increased two-fold in 3 days. The ER mRNA level increased 1.5-fold and the uterine weights were doubled. The plasma estradiol concentration did not change during the treatment. A separate experiment was carried out to establish whether IGF-I itself exercises estrogen-like effects. Ovariectomized rats were given hrIGF-I in osmotic minipumps for 3 days. The uteri of the treated animals weighted significantly more than did the controls. Quantitation of the level of uterine estrogen receptors revealed a significant decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Cervical ripening in humans: potential roles of estrogen, progesterone, and insulin-like growth factor-I.

OBJECTIVE During pregnancy in humans a gradual connective tissue remodeling takes place in the cervix. The aim of this study was to examine a possible relationship between the action of gonadal steroids and growth factors and the biochemically identifiable changes in connective tissues during cervical ripening. STUDY DESIGN Cervical biopsy specimens and serum samples were taken from 20 term pregnant and 20 nonpregnant menstruating women. Estrogen receptors and progesterone receptors were measured with enzyme immunoassays. The messenger ribonucleic acid levels for estrogen receptors, progesterone receptors, and insulin-like growth factor-I were determined by solution hybridization with human complementary deoxyribonucleic acid probes. The concentration of collagen and its solubility by pepsin digestion were measured. Statistical evaluations were done with the Student t test. RESULTS In term pregnancy the estrogen receptor level decreased to 14% and the progesterone receptor level to 24% of nonpregnant levels (p <0.001 and p <0.01). The insulin-like growth factor-I messenger ribonucleic acid level increased 400% (p <0.01), whereas the messenger ribonucleic acid levels for estrogen receptors and progesterone receptors were unchanged. The changes coincided with a twofold decrease in collagen concentration (hydroxyproline) and a twofold increase in collagen solubility. CONCLUSION Estrogen receptors and progesterone receptors are present in human cervix. A significant down-regulation of estrogen receptors and progesterone receptors and a fourfold increase in the insulin-like growth factor-I messenger ribonucleic acid level were registered in term pregnant cervix. These findings coincided with the remodeling of the cervical connective tissue.

Effects of SERM (selective estrogen receptor modulator) treatment on growth and proliferation in the rat uterus.

BackgroundSelective estrogen receptor modulators (SERMs) have been developed in order to create means to control estrogenic effects on different tissues. A major drawback in treatment of estrogen receptor (ER) positive breast cancer with the antagonist tamoxifen (TAM) is its agonistic effect in the endometrium. Raloxifene (RAL) is the next generation of SERMs where the agonistic effect on the endometrium has been reduced.MethodsThe aim of the present study was to determine the effect of SERM treatment on the uterus, as assessed by proliferation markers and several factors involved in uterine growth. Ovariectomized (ovx) rats were treated with estradiol (E2), tamoxifen (TAM), RAL, ICI182780 (ICI) or vehicle (OVX-controls). We studied the effects on mRNA levels of the growth hormone (GH) receptor, insulin-like growth factor-I (IGF-I), ERα and ERβ. In addition, by immunohistochemistry the proliferation markers PCNA and Ki-67, as well as ERα and ERβ, were detected.ResultsThe uterine weight of the rats treated with E2 or TAM was increased as compared to OVX-controls. The uterine GH-receptor mRNA level was highest in the E2 treated animals. In ICI treated rats no GH-receptor mRNA could be detected. The IGF-I mRNA level increased 16-fold in uteri of the TAM treated group and 9-fold in the E2 treated rats as compared to OVX-controls. The ERα mRNA level was increased in the E2 treated rats, while the ERβ mRNA level was increased after TAM treatment. The proliferation, as assessed by PCNA, was lowest in ICI treated animals.ConclusionsThe uterine wet weight, the LE height and the GH-receptor mRNA levels showed similar patterns, indicating that GH is involved in the regulation of uterine weight. Tamoxifen, which has been related to increased incidence of endometrial carcinoma in women, dramatically increased IGF-I mRNA levels in rat uterus. Since proliferation was not higher in TAM and E2 treated rats than in OVX controls, this assay of simple, early proliferation does not give the full explanation of why TAM should enhance the risk of developing endometrial cancer.

Identification of wild type and variants of oestrogen receptors in polymorphonuclear and mononuclear leucocytes

Objective   Leucocytes play an important role in the pathogenesis of autoimmune and cardiovascular diseases. Clinical and epidemiological observations indicate that the sex steroid hormones, particularly oestrogens, may regulate leucocyte functions. The assumption that oestrogens have a direct effect on leucocytes has to be supported by identification of functional oestrogen receptors (ER) in leucocytes. This study aimed at investigating the presence of ER subtypes in different types of leucocytes isolated from peripheral blood of female and male donors.

The estrogen receptor in the rat kidney. Ontogeny, properties and effects of gonadectomy on its concentration

Estrogens have been suggested as modulators of the conversion of 25-hydroxyvitamin D3 to dihydroxylated compounds in the kidney. In order to further explore this hypothesis the estrogen-binding components in the kidney were studied in adult and immature rats. The basal receptor levels in adult animals were 9.6 fmol/mg protein (female) and 21.9 (male). The receptor-ligand complex had a Kd of 0.7 nM. Furthermore, the kidney receptor displayed similar characteristics as those of the cytosol liver estrogen receptor in terms of sedimentation properties on sucrose gradients, isoelectric focusing and ligand binding specificity. The ontogeny of cytosol high affinity estrogen binding sites was elucidated in female and male animals. Detectable levels of receptors (5 fmol/mg protein) were found during the first postnatal week in both sexes. During days 22-25 receptors reached maximum concentrations at about 30 fmol/mg protein. In the male this level then remained relatively constant throughout the time of study (60 days), whereas in the female the concentration decreased gradually over a period of 12-15 days to a basal level of 10 fmol/mg protein. A temporal study on the short- and longterm effects of ovariectomy on the concentration of estrogen binding sites in the kidney cytosol was also carried out. Shortly after gonadectomy (2-12 h) no effect was detected. During 20-48 h after the operation a 75% increase in the receptor level was seen. The results indicate a multihormonal control of the estrogen binding protein in the kidney similar to that seen in the liver. Furthermore, the data suggest that estradiol down-regulate its own receptor. The results are discussed in relation to present concepts on the actions of estrogens and the metabolism of vitamin D3.

Effects of estradiol-17α on nuclear occupancy of the estrogen receptor, stimulation of nuclear type II sites and uterine growth

Estriol and estradiol-17 alpha (E2-17 alpha) have classically been described as weak or impeded estrogens since they are incapable of stimulating true uterine growth when administered acutely by single injection. We have demonstrated [16] that estriol is capable of stimulating true uterine growth when the hormone is administered by paraffin implant. The possibility that E2-17 alpha is similar to estriol was examined. A single injection of E2-17 alpha causes a rapid accumulation of the estrogen receptor in uterine nuclei and this is correlated with the stimulation of early uterotropic responses. The nuclear receptor content declines rapidly and no stimulation of nuclear type II sites or true uterine growth is observed. E2-17 alpha does however stimulate the replenishment of cytoplasmic estrogen receptor. This receptor-response profile is typical of a short acting estrogen such as estriol. Chronic exposure (96 h) of mature-ovariectomized rats to estradiol-17 alpha (4 mg) by beeswax implant results in continual nuclear occupancy by estrogen receptors, dramatic stimulation of nuclear type II sites and true uterine growth. It is not possible to determine whether the uterotropic stimulation was due to direct effects of E2-17 alpha since this isomer was partially metabolized to E2-17 beta and both isomers were found in uterine nuclei after an implant of E2-17 alpha. We conclude that E2-17 alpha is capable of acting as an estrogen, either by its inherent estrogenicity or by its conversion to E2-17 beta, and that it may be dangerous to consider this steroid to be an ineffective or inadequate estrogen.

Androgen regulation of the insulin-like growth factor-I and the estrogen receptor in rat uterus and liver

For the first time testosterone is shown to be an important regulator of the insulin-like growth factor-I (IGF-I) in the rat uterus under in vivo conditions. In this study the regulation of IGF-I and the estrogen receptor (ER) by gonadal steroids in the uterus and liver of female rats was monitored. The ER level was assayed by hormone binding after treatment with testosterone, 5 alpha-dihydrotestosterone or estradiol and specific mRNA species were analyzed by a solution hybridization/RNase protection assay using 35S-labeled RNA probes. Ovariectomized rats restored uterine weight after treatment with testosterone. Uterine IGF-I mRNA was more than 20-fold higher in testosterone treated rats compared to untreated ovariectomized controls after 48 h treatment. The effects of testosterone on ovariectomized animals was followed in a timecourse study. Testosterone administration increased uterine IGF-I mRNA expression during the first 48 h and the maximally induced level was maintained throughout the duration of the experiment (168 h). Since induction of IGF-I mRNA by estrogen is transient, these data indicate that androgen and estrogen increase IGF-I mRNA by different mechanisms. Regulation of IGF-I mRNA by gonadal steroids was also studied in hypophysectomized animals. The rats were given either testosterone, 5 alpha-dihydrotestosterone or estradiol, and uterine IGF-I mRNA was measured after 1 week of treatment. At this timepoint estrogen treated rats showed levels of IGF-I mRNA not significantly different from those of hypophysectomized controls. In contrast testosterone and 5 alpha-dihydrotestosterone increased the IGF-I mRNA level 30 and 40 times, respectively, relative to hypophysectomized control animals. Since 5 alpha-dihydrotestosterone is not convertable to estrogen, the induction by testosterone was considered to be a true androgenic phenomenon.

The Biology and Pharmacology of Estrogen Receptor Binding: Relationship to Uterine Growth

Publisher Summary The accumulation of the receptor-estrogen (RE) complex by the nucleus is not sufficient to elicit true growth of the uterus. Even though the initial accumulation is correlated with the stimulation of early uterotropic events, true uterine growth results only when the RE complex remains bound in the nucleus for six hours or longer. This long-term nuclear retention of the RE complex is accompanied by the stimulation of a second elevation in RNA polymerase II activity and a sustained stimulation of RNA polymerase I activity. These responses may be characteristic of the obligatory response profile that is associated with true uterine growth. The chapter also shows that long-term nuclear retention may result from two different binding states of the RE complex in the nucleus: (1) one tightly bound form to chromatin, which is called KCl resistant and (2) another more loosely bound form, which is called KCl extractable. These two forms show quantitative and temporal relationships that suggest that the KCl-resistant form is derived from the KCl-extractable form.