Cytosol Estrogen Receptor Concentrations Research Articles

Cytosolic estrogen and progesterone receptor content in the endometriotic tissues and endometrium in women with and without endometriosis

In order to have a profile of cytosolic estrogen and progesterone receptors in either endometriotic tissue or endometrium in patients with and without endometriosis a cross-sectional study was  performed  involving  43  infertile women. They consisted of 31 (72.09%) endometriosis and 12 (27.91%) non-endometriosis cases; their average age was 32 ±4 years and 32  ±3 years respectively, with the average  length  of  menstrual  cycle  31  ±8  days  and  29  ±1  days  respectively.  The endometriotic tissue was obtained by excision during ope-rative laparoscopy procedure, while the endometrium was obtained  by  biopsy following hysteroscopy  procedure.  These procedures  were  conducted  within  the  periovulatory  period  (on  Day  13-18  of  the  cycle).The  sex  steroid  receptor  content  in  the cytosol  was  measured  quantitatively  using enzyme-immunoassaymethod,  and  calculated  as  sex  steroid  receptor/cytosol  protein (fmol/ml  cytosol).  It  was  found  that  the  average cytosolic estrogen  receptor concentration  in  the  respective  tissues  were 512.99fmol/ml  in  the  endometriotic  ovary compared  with  2369.17  in  normal  ovary and  632.18  fmol/ml  in  the  endometriotic  peritoneum compared  with  9607.61  fmol/ml  in  normal  peritoneum;while 99.28  fmol/ml and 608.33fmol/ml in the endometrium of women with endometriosis and those without endometriosis respectively. The average cytosolic progesterone receptor concentration found in the respective  tissues  were 50.64fmol/ml  in  the  endometriotic  ovary compared  with  6469.42  fmol/ml  in  normal  ovary and1631.40 fmol/ml  in  endometriotic  peritoneum compared with 12466.99 in normal peritoneum, while21.26 fmol/ml and 599.61fmol/ml in the endometrium  of  women  with  endometriosis  and  those  without  endometriosis  respectively.  There  is  no  significant difference in the  receptor concentration  between  each  tissue  according  to  its  topographic  origin. However,  this  result  may  assume  that  the  responsivity  on  hormonal treatment in endometriosis cases willdepend on the cytosolic sex steroid receptor content in the sick tissues, and the peritoneal lesions will possibly give better response than those in other sites. A further clinical trial is necessary. (Med J Indones 2005; 14: 133-41)

Sex differences in estrogen receptor binding in the rat hypothalamus: effects of subsaturating pulses of estradiol

The effects of subsaturating pulses of estradiol on cell nuclear retention of estrogen receptors in brain regions of male and female rats was determined. In the first experiment, age-matched adrenalectomized/gonadectomized (ADX/GDX) rats were killed 1 h after i.v. injection of a subsaturating dose of free estradiol (1.0 μg/kg b. wt.) and cell nuclear estrogen receptor binding was measured in microdissected brain areas by an in vitro exchange assay. As we have previously reported with saturating doses of estradiol (3.6–36.0 μg/kg b. wt.), a greater concentration of receptors was measured in the ventromedial nucleus (VMN), periventricular preoptic area (PVPOA), and medial preoptic area (mPOA) of the female than in the same regions of the male brain. Binding levels did not differ between the sexes in the bed nucleus of the stria terminalis, arcuate nucleus, or the corticomedial amygdala. In the second experiment, GDX/ADX male and female rats received either a single or double pulse of 0.5 μg estradiol/kg b. wt. administered 6 h apart. Rats were killed 1 h after the second pulse. In animals treated with a single pulse of estradiol 1 h before sacrifice, higher concentrations of estrogen binding were measured in the female VMN and PVPOA than in the male. Except in the mPOA, the concentration of estrogen receptor binding measured was not different from that measured in animals that had received an additional, earlier pulse of estradiol. In this area, receptor concentrations were lower in male rats treated with two pulses than in males treated with one pulse. Thus, receptor dynamics in the mPOA of the male may differ from that of the female and from that of other brain regions. In the third experiment, cytosol estrogen receptor concentrations measured in untreated male and female GDX/ADX rats were compared. Consistent with our data on cell nuclear binding after exposure to estradiol, cytosol receptor concentrations in the female VMN, PVPOA and mPOA were greater than those in the male. These results extend our previous findings of regional sex differences in maximal cell nuclear estrogen binding capacity by demonstrating that these differences exist in the presence of subsaturating pulses of estradiol and that they reflect differences in cytosol estrogen receptors.

Effects of the β-isomer of hexachlorocyclohexane on estrogen-sensitive human mammary tumor cells

The effects of the β-isomer of hexachlorocyclohexane (β-HCH) on the induction of the cytosolic progesterone receptor (PgRc), on the redistribution of the estrogen receptor (ER), and its affinity for ER were investigated in the estrogen-sensitive human mammary tumor cell line MCF-7. The effects of β-HCH were compared to those of estradiol-17β (E 2) and 2,4,6-trichlorophenol (TCP), a major urinary metabolite of β-HCH in rats. β-HCH in concentrations higher than 1 μ m caused induction of PgRc whereas TCP was essentially without effect up to a cytotoxic concentration of 100 μ m. Furthermore, β-HCH (10 μ m) caused redistribution of ER, i.e., decrease of cytosolic ER concentration and increase of nuclear ER concentration, in a way similar to E 2. In contrast to this, β-HCH up to a molar excess of 6 × 10 4 (concentration 30 μ m) caused no significant displacement of [ 3H]E 2 from ER indicating that β-HCH has no substantial affinity for ER. It is concluded that β-HCH has estrogenic properties which are at variance with the failure to demonstrate binding of β-HCH to ER.

Development of progesterone-facilitated lordosis in female guinea pigs: relationship to neural estrogen and progestin receptors

Ovariectomized (OVX), 20-day-old female guinea pigs did not exhibit lordosis following treatment with estradiol benzoate (EB) and progesterone. Behavioral responsiveness to EB and progesterone developed abruptly; by 30 days of age, responses typical of adult females (>9weeks of age) were observed. In vitro assays of neural steroid receptors were performed to test the hypothesis that a deficiency in the concentration of hypothalamic and/or preoptic area estrogen and/or progestin receptors contributes to the lack of progesterone-facilitated lordosis in juvenile (20-day-old) females. Assay of cytosol progestin receptors in the mediobasal hypothalamus (MBH) and preoptic area (POA) of immature and adult females 40 h after injection of EB confirmed a previous report that the concentration of estradiol-induced cytosol progestin receptors in the MBH of juvenile females was slightly lower than that observed in adults. Furthermore, MBH cell nuclear accumulation of progestin receptors after progesterone injection was markedly lower (i.e. 42%) in immature, as compared to adult females. The concentrations of cytosol estrogen receptors in the MBH and POA did not differ between immature and adult OVX guinea pigs. Also, cell nuclear estrogen receptor accumulation in the MBH after estradiol injection was comparable in immature and adult females. These data suggest that a deficiency in cell nuclear progestin receptor accumulation in the MBH may contribute to the absence of progesterone-facilitated lordosis in estradiol-primed, immature female guinea pigs. This age-related difference in cell nuclear progestin receptor accumulation may be due, in part, to reduced concentrations of estradiol-induced cytosol progestin receptors. However, the deficient response to estradiol in immature females does not appear to be the result of reduced levels of cytosol estrogen receptors or to aberrant cell nuclear estrogen receptor accumulation in the MBH.

Nuclear estrogen receptor binding in the preoptic area and hypothalamus of pregnancy-terminated rats: correlation with the onset of maternal behavior.

Terminating the pregnancies of female rats on day 16 (D 16) by hysterectomy and ovariectomy (HO) and administering estradiol benzoate (EB) systemically or centrally into the medial preoptic area (MPOA) stimulates the onset of maternal behavior 48 h later. Since estrogen's effects are mediated through its intracellular receptors, the present studies measured nuclear and cytosol estrogen receptor concentrations in the POA and hypothalamus (HYP) of female rats during the 48 h when estrogen is active in stimulating maternal behavior. A low dose of EB (5 micrograms/kg) was used which was effective in stimulating maternal behavior in D16HO females but not in nonpregnant HO females of two types. In D16 animals there was a significantly higher concentration of nuclear receptors in the POA than in the HYP at time 0 (before HO and EB) but thereafter levels were similar in the two areas: nuclear receptor levels rose between 6 and 24 h after which they declined. In nonpregnant females, nuclear receptor levels at time 0 were low in both brain regions, rose significantly between 0 and 24 h, and significantly declined between 24 and 48 h similar to the D16 females. There were minimal differences in cytosol receptor levels among all groups at any time. Results from additional groups, nonpregnant HO females given 100 micrograms/kg EB and D16H animals (females whose pregnancies were terminated by hysterectomy only and their ovaries left intact), both of which exhibit maternal behavior at 48 h, support the idea that a high level of nuclear estrogen receptors in the POA followed by a sustained high level is necessary for estrogen stimulation of maternal behavior.

Further evidence of noradrenergic regulation of rat hypothalamic estrogen receptor concentration: possible non-functional increase and functional decrease

The regulation of estrogen receptors by the α 2-noradrenergic system was studied. A single injection of the α 2-noradrenergic antagonist, yohimbine, caused a biphasic effect on the concentration of cytosol estrogen receptors in the mediobasal hypothalamus and anterior pituitary gland. A short-latency increase was seen at 1.5–3 h, followed by a longer-lasting decrease at 8–16 h. Scatchard analysis revealed that the apparent, short-latency increase is in the concentration of binding sites, not in the affinity of the receptor for [ 3H]estradiol. The increase in the concentration of cytosol estrogen receptors is not blocked by pretreatment with the α 2-noradrenergic agonist, clonidine. In addition, no increase is detected in the concentration of cell nuclear estrogen receptors accumulating in response to a saturating dose of estradiol. Therefore, the apparent increase in the concentration of cytosol estrogen estrogen may not represent a functional increase in receptors. The decrease in the concentration of estrogen receptors, which occurs 8–16 h after yohimbine treatment, is also seen after injection of the α 2-nodrenergic antagonist, idazoxan, and is not due to a change in the in vitro rate of association of the receptors with [ 3H]estradiol. Furthermore, the decrease seems to be a functional decrease in the concentration of receptors capable of cell nuclear accumulation in response to estradiol injection, as indicated by the results of experiments in which the concentration of cell nuclear estrogen receptors was assayed after estradiol injection. These experiments provide further support for the hypothesis that the α 2-noradrenergic system, and perhaps specifically the α 2-subtype, is involved in decreasin the concentration of es receptors in parts of the brain and pituitary gland. This interaction provides a mechanism by which the environment could regulate the sensitivity of certain neurons to estradiol. However, the finding that the initial increase in the concentration of cytosol estrogen receptors after yohimbine treatment is not followed by the predicted in cell nuclear estrogen receptors after estradiol injections raises questions about the physiological relevance of the apparent increaseunder conditions.

Small apomorphine-induced increase in the concentration of cytosol estrogen receptors in female rat hypothalamus and pituitary

A series of experiments was performed to investigate the previously-reported modulation of estradiol binding in female rat brain and pituitary gland by drugs that influence the dopaminergic system. Injection of the dopamine agonist, apomorphine, at minimum doses of 1–2 mg/kg body weight caused slight increases (in most cases, less than 10%) in the concentration ofcytosol estrogen receptors in the mediobasal hypothalamus and anterior pituitary gland without influencing the concentration in the preoptic area. However, after subsequent injection of a saturating dose of estradiol, the level of nuclear estrogen receptors accumulating did not differ significantly between apomorphine-treated animals and vehicle-injected controls. These results extend, in part, previous reports that have shown an apomorphine-induced increase in the concentration of [ 3H]estradiol in brain and pituitary cell nuclei after an injection of [ 3H]estradiol. However, we failed to observe differences in the concentration of cytosol estrogen receptors as large as would be expected by previous work, and we failed to observe differences in the concentration of nuclear estrogen receptors after estradiol injection.

The α 1-noradrenergic antagonist prazosin decreases the concentration of estrogen receptors in female rat hypothalamus

A series of experiments was performed to determine the effects of the α 1-noradrenergic antagonist, prazosin, on the concentration of estrogen receptors in female rat brain and pituitary gland. Prazosin caused a dose-dependent decrease in the concentration of cytosol estrogen receptors in fediobasal hypothalamus when injected 10 and 16 h prior to assay. The drug was without effect on the concentration of nuclear estrogen receptors in the absence of estradiol, indicating that the decreased concentration of cytosol estrogen receptors is not due to nuclear estrogen receptor accumulation. Scatchard analysis confirmed that prazosin treatment decreases the conceptors of cytosol estrogen receptors without influencing the apparent affinity of the receptors for [ 3H]estradiol. The prazosin-induced decrease in the concentration of cytosol estrogen receptors in the mediobasal hypothalamus was transient with maximal effects occurring between 8 and 12 h after a single injection. Competition analysis confirmed that prazosin is not an effective competitor for binding to the estrogen receptor in vitro. The effects of prazosin on the estrogen receptor system could not be attributed to modulation of the levels of norepinephrine or dopamine. Assay of the levels of norepinephrine and dopamine in hypothalamus and preoptic area after prazosin injection revealed no effects of prazosin on the level of either of these catecholamines. An estradiol injection resulted in the predicted decrease in the concentration of estrogen receptors accumulating in hypothalamic cell nuclei, suggesting that the cytosol estrogen receptors that decrease in concentration are functional receptors. Prazosin treatment did not result in a decrease in the effectiveness of estradiol in the induction of cytosol progestin receptors in the mediobasal hypothalamus, suggesting that the cells are regulated by the α 1-noradrenergic system may not be those cells in which progestin receptors are also induced. These experiments provide further evidence that the noradrenergic system modulates the concentration of estrogen receptors, and perhaps sensitivity to estradiol, in some cells within the rat hypothalamus.

Noradrenergic regulation of cytosol estrogen receptors in female rat hypothalamus: possible role of ga 2-noradrenergic receptors

Because of the previous work demonstrating that the α 1-noradrenergic receptor antagonist , prazosin, decreases the concentration of cytosol estrogen receptors in rat mediobasal hypothalamus, a series of experiments was performed to determine the specificity of this effect of the α 1-noradrenergic system. Injection of the α 2-noradrenergic antagonist, yohimbine, caused a decreased in the concentration of estrogen receptors in mediobasal hypothalamus. In addition, the down-regulation of cytosol estrogen receptors by either the α 1-noradrenergic antagonist, prazosin, or the α 2noradrenergic antagonist, yohimbine, could be blocked by pretreatment with the α 2noradrenergic agonist, clonidine. The α 1-noradrenergic agonist, phenylephrine, was ineffective in blocking the effects of the α 1-noradrenergic antagonist, prazosin. These results add further support to the hypothesis that the α-noradrenergic system modulates the concentration of cytosol estrogen receptors in the rat hypothalamus. They suggest that the modulation may occur by way of α 2-noradrenergic receptors in addition to, or instead of, α 1-noradrenergic receptors.

Rat cerebral cortical estrogen receptors: Male-female, right-left

We determined the concentration of cytosol estrogen receptors in the postnatal, developing right and left cerebral cortices of Long-Evans male or female rats 2 to 3, 7 to 8, 14 to 15, and 25 to 26 days of age. Under anesthesia, the rats were gonadectomized and 24 h later they were killed by decapitation, and the dorsal right and left cerebral cortices were separated from the underlying white matter and placed on ice. Sephadex LH-20 gel filtration chromatography was used to dissociate the majority of alpha-fetoprotein-bound [ 3H]estradiol while leaving the receptor [ 3H]estradiol complex intact. The correction for the residual nonreceptor binding, including alpha-fetoprotein, was made using parallel incubation containing unlabeled diethylstilbesterol. The amount of residual nonreceptor binding was subtracted from [ 3H]estradiol-bound protein to calculate high-affinity estradiol binding receptors. The results showed that in both sexes, estrogen receptor concentration was highest at postnatal days 2 to 3 in both the right and the left cerebral cortex and then decreased until 25 days of age. In the female, the right cerebral cortex, at postnatal day 2 to 3, had a higher estrogen receptor concentration than the left cortex ( P < 0.02). In the male, the left cortex had a higher cytoplasmic estrogen receptor concentration ( P < 0.02) than the right. Considering the reported growth-inhibiting effects of estrogen on the cerebral cortex, the results indicated that one determinant of cerebral dominance in both sexes may be the differential exposure to estrogen, in the case of the male testosterone converted to estrogen, during a critical period of development.

Biochemical and histologic effects of sequential estrogen/progestin therapy on the endometrium of postmenopausal women

Medroxyprogesterone acetate in doses of 10, 5, and 2.5 mg was administered sequentially to three groups of postmenopausal women receiving 0.3 mg, 0.625 mg, and 1.25 mg of conjugated equine estrogens, respectively. Serial endometrial biopsies were performed on these women before therapy, during estrogen therapy alone, and during sequential estrogen-progestin therapy. Endometrial histology and estrogen receptor concentrations were assessed. A linear increase of cytosolic estrogen receptor concentration occurred over the dosage range of conjugated equine estrogen. When medroxyprogesterone acetate was added to the estrogen therapy, the concentrations of estrogen receptors fell. Within the groups of women receiving 0.3 mg and 0.625 mg of conjugated equine estrogen, all doses of medroxyprogesterone acetate were equally effective in reducing the levels of cytosolic receptor to pretreatment levels. However, at the conjugated equine estrogen dose of 1.25 mg, only 5 mg and 10 mg doses were effective in reducing the cytosolic receptor concentration to pretreatment levels. Histologically, little effect was observed from the lowest doses of either drug. However, even though 5 and 10 mg of medroxyprogesterone acetate were identical biochemically, the 10 mg dose was the only one producing a homogeneous, secretory pattern within the endometrium.

Dopamine-beta-hydroxylase inhibitors modulate the concentration of functional estrogen receptors in female rat hypothalamus and pituitary gland.

In order to study further the regulation of steroid hormone receptors in the brain and anterior pituitary gland of ovariectomized rats by catecholamines, the influence of two dopamine-beta-hydroxylase inhibitors on the estrogen receptor system was studied. The two inhibitors, FLA 63 and diethyldithiocarbamate (DDC) both caused a biphasic effect on the concentration of cytosol estrogen receptors in the mediobasal hypothalamus without influencing the concentration of cell nuclear estrogen receptors in the absence of estradiol; the concentration of cytosol estrogen receptors first increased and then decreased after treatment. In a study of the neuroanatomical areas in which inhibition of dopamine-beta-hydroxylase decreases the concentration of cytosol estrogen receptors, it was found that the concentration of cytosol estrogen receptors decreased after drug treatment in the mediobasal hypothalamus and preoptic area-septum, but not in the amygdala. This suggests that the decrease in concentration of hypothalamic cytosol estrogen receptors caused by dopamine-beta-hydroxylase inhibitors is not a nonspecific effect on all cytosol estrogen receptors. Finally, an injection of estradiol-17 beta in animals that had been pretreated with either DDC or FLA 63 resulted in less accumulation of cell nuclear estrogen receptors in those tissues in which the drug first caused a decrease in the concentration of cytosol estrogen receptors than in vehicle-injected controls. Therefore, under some conditions, pretreatment with a dopamine-beta-hydroxylase inhibitor decreased the concentration of functional cytosol estrogen receptors resulting in decreased nuclear estrogen receptor accumulation in response to an estradiol injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Some catecholamine inhibitors do not cause accumulation of nuclear estrogen receptors in rat hypothalamus and anterior pituitary gland.

We have recently shown that the dopamine-beta-hydroxylase inhibitor, U-14,624, decreases the concentration of cytosol estrogen receptors in the mediobasal hypothalamus (MBH) and anterior pituitary gland (AP) in ovariectomized rats, but that it also causes cell nuclear accumulation of estrogen receptors. We tried to determine if this is the mechanism by which other catecholaminergic inhibitors decrease the concentration of cytosol estrogen receptors in either the MBH or AP. The previously reported decrease in the concentration of cytosol estrogen receptors in AP by the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine was confirmed. Also, the decrease in the concentration of cytosol estrogen receptors in MBH after treatment with the dopamine-beta-hydroxylase inhibitors, diethyldithiocarbamate and FLA 63 was demonstrated. In no case was an increase in the concentration of nuclear estrogen receptor accumulation detected after treatment with the drugs. Results of assays of norepinephrine and dopamine levels in MBH after the various treatments suggest that, at the dosage used, U-14,624 has a greater effect on norepinephrine and dopamine levels that the other dopamine-beta-hydroxylase inhibitors. The results of these experiments suggest that inhibitors of dopamine-beta-hydroxylase and tyrosine hydroxylase cause decreases in the concentration of cytosol estrogen receptors in either the MBH or AP that are not referable to increased cell nuclear accumulation of estrogen receptors.

Cell nuclear accumulation of estrogen receptors in rat brain and pituitary gland after treatment with a dopamine-beta-hydroxylase inhibitor.

In a recent experiment, it was found that the dopamine-beta-hydroxylase inhibitor, U-14,624, decreases the concentration of cytosol progestin receptors in guinea pig hypothalamus and causes an increase in the concentration of nuclear progestin receptors. In this series of experiments, the possibility that similar effects would be seen in the rat estrogen receptor system in mediobasal hypothalamus and pituitary was tested. U-14,624 caused a time-dependent decrease in the concentration of cytosol estrogen receptors and increase in the concentration of nuclear estrogen receptors in both mediobasal hypothalamus and anterior pituitary gland in ovariectomized rats, both in the absence and presence of low levels of estradiol, as well as in ovariectomized-adrenalectomized rats. The nuclear estrogen receptors that accumulate after U-14,624 injection do not require incubation at 25 degrees C to be assayed, suggesting that they are not occupied by an estradiol-like ligand. The nuclear estrogen receptors that accumulate after U-14,624 treatment are high affinity, with an apparent dissociation constant of approximately 0.1 nM. U-14,624 does not compete with (3H)estradiol, in vitro, suggesting that it does not directly interact with estrogen receptors. These results suggest that under some conditions, inhibition of dopamine-beta-hydroxylase causes a modification in unoccupied estrogen receptors so that they develop a higher affinity for cell nuclear components.

Cytosol and nuclear estrogen and progestin receptors and 17 beta‐hydroxysteroid dehydrogenase activity in non‐diseased tissue and in benign and malignant tumors of the human ovary

Significant but low concentrations (mean 8 fmol/mg cytosol protein) of cytosol estrogen receptors were found in 57% of non-diseased ovarian tissues, and higher concentrations (mean 211) of cytosol progestin receptors in all these tissues. An approximately similar distribution was found for the presence of nuclear female sex steroid receptors; the mean concentrations were 159 and 1149 sites/cell, for estrogen and progestin receptors, respectively. There were no major differences in these parameters between pre- and postmenopausal non-diseased ovaries. The activities of ovarian 17 beta-hydroxysteroid dehydrogenase (17-HSD) did not display correlations between circulating progesterone concentrations in pre- or postmenopausal women with non-diseased ovaries. The majority of benign epithelial tumors contained significant concentrations of cytosol estrogen receptors, and all showed cytosol progestin receptors. The concentration of estrogen receptors was identical to that seen in non-diseased ovaries (mean 9 fmol/mg cytosol protein), whereas that of progestin receptor was significantly lower (mean 95). Nuclear female sex steroid receptors were measured in all benign tumors, and their concentrations were significantly higher than in normal ovaries (440 and 3218 sites/cell for estrogen and progestin receptors, respectively). No difference in 17-HSD activities were detected between normal ovaries and benign tumors. In malignant ovarian tumors, the picture was different from that found in normal ovarian tissues and benign tumors. Cytosol estrogen receptor was found in 89% of malignant epithelial tumors, and its concentration was significantly higher (mean 64 fmol/mg cytosol protein). Cytosol progestin receptor was found in 91%, and its concentration (mean 75) was significantly lower than in normal ovarian tissue or benign ovarian tumors. Nuclear female sex steroid receptor concentrations were intermediate between those seen in non-diseased ovaries an in benign tumors. 17-HSD activity was significantly lower than in other tissue categories studied. In the small group (16) of non-epithelial ovarian carcinomas cytosol estrogen receptors were not found, whereas the results of other measurements did not display any coherent picture. Breast and endometrial carcinoma metastatic to the ovary showed receptor patterns which were typical of the primary tumors. When the different clinical stages (I-IV) of malignant epithelial ovarian tumors were compared, 17-HSD activity was significantly higher in the least advanced clinical stage (I), whereas no significant differences were found in the other parameters measured.(ABSTRACT TRUNCATED AT 400 WORDS)

Correlation between oxytocin receptor concentration and responsiveness to oxytocin in pregnant rat myometrium: effects of ovarian steroids.

Marked changes in the uterine binding of oxytocin (OT) occur in rats at the time of parturition or after treatment of ovariectomized rats with estrogen or progesterone. To ascertain that these binding sites represent the biological receptors for OT, we measured the uterine response to OT in various groups of rats in which specific OT binding was also determined. Intact pregnant rats and rats ovariectomized on day 20 of gestation and treated thereafter with oil, estradiol benzoate (5 micrograms/24 h), progesterone (5 mg/24 h), or estradiol and progesterone together had indwelling balloons inserted on day 20 for the recording of uterine response to either iv bolus injections or iv infusions of OT. The uterus was removed 24-48 h after balloon insertion, and OT binding to the particulate fraction as well as nuclear estrogen and cytosolic estrogen receptor concentrations were determined. An inverse correlation (r2 = 0.758) was found between the concentration of OT-binding sites and the threshold dose of OT, and a linear correlation was found between the concentration of binding sites and the uterine activity induced by OT infusion (r2 = 0.852). We conclude, therefore, that the high affinity (Kd, 1-2 nM) binding sites for OT represent the physiological receptors. The concentration of these sites increased progressively during estrogen treatment. Progesterone completely inhibited this estrogen-induced rise. After ovariectomy, there was a modest, but significant, increase in OT receptor concentration which also was prevented by progesterone. The increase in OT receptor concentration was correlated with the estrogen receptor concentration in intact pregnant and estrogen-treated ovariectomized animals, but not in the other groups of animals. The apparent affinity of the receptors for OT was not significantly affected by hormone treatment. We conclude that the concentration of receptors is a major factor controlling the uterine responsiveness to OT, and that the receptor concentrations are regulated by ovarian hormones in a manner related to estrogen receptor activation. In addition, estrogen appeared to enhance the coupling of OT receptor occupancy to the tissue response to OT.

Alterations in sex-steroid hormone receptors during mammary gland differentiation in the rat

1. 1. Sprague-Dawley and Wistar strains were the best tissue sources for the estrogen receptors of the mammary gland of 7 rat strains examined. 2. 2. Tissue DNA content reached a maximum in late lactation (15–19 days). 3. 3. Cytosolic protein concentrations reached a maximum in late lactation (15–19 days). 4. 4. Both tissue DNA and cytosolic protein concentrations decreased upon weaning. 5. 5. The dissociation constant of the cytosolic estrogen receptor showed little change in pregnancy and lactation. 6. 6. The cytosolic estrogen receptor concentration was maximal at 19 days lactation. 7. 7. The cytosolic protesterone receptor was undetectable in late pregnancy (14–20 days) and in mid and late lactation (10–19 days).

A decrease of cytosol estrogen receptors in the hypothalamus as a result of treatment of neonatal rats with glutamate.

Experiments were performed to determine whether the neuroendocrine dysfunctions of rats treated neonatally with monosodium glutamate (MSG) could be related to a loss of cytoplasmic estrogen receptors. Female rats treated with MSG as neonates were ovariectomized as adults and killed by decapitation 2 or 3 weeks after ovariectomy. Body, gonadal and anterior pituitary gland weights in MSG-treated rats were depressed when compared to that seen in their littermate controls. Serum prolactin concentration was elevated in the MSG-treated rats. Serum luteinizing hormone (LH) concentration was significantly lower in MSG-treated rats than in controls at 2 weeks, but not at 3 weeks after ovariectomy, suggesting a sluggish postovariectomy rise of serum LH concentration. Serum follicle-stimulating hormone (FSH) concentration was not altered by the MSG treatment. The concentration of cytosol estrogen receptors in the anterior pituitary gland was similar to that of controls, but hypothalamic concentration of estrogen receptors decreased as a result of the MSG treatment. After dissection of different hypothalamic regions, it was found that the greatest depletion of the cytosol estrogen receptors occurred in the arcuate-median eminence region. The results raise the possibility that some reproductive impairments of MSG-treated rats could stem from a decrease in cytosol estrogen receptors in the arcuate-median eminence region.

Estrogen and progestin receptors in intracranial meningiomas

Tissue samples from 16 meningioma patients were analysed for the cytosolic estrogen receptor concentration using isoelectric focusing and 11 of the 16 cases were also analysed for the cytosolic progestin receptor concentration using sucrose gradient centrifugation. In this study, 15 of the 16 (94%) and 9 of the 11 (82%) meningiomas had detectable estrogen and progestin receptors, respectively. The mean estrogen receptor concentration in female subjects was 8.9 fmol/mg protein and in males 3.0 fmol/mg protein. This sexual difference in receptor content was statistically significant. When the progestin receptor concentrations were plotted against the estrogen receptor concentrations in the same tumors, a relatively good positive correlation was obtained in female patients ( r = 0.87). These findings confirm and extend previous reports on the existence of sex steroid receptors in human brain tumors and might open up the possibility of selective endocrine therapy against meningiomas, especially in case of poorrisk patients.