Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have produced a truncated form of the human estrogen receptor (hER) as a fusion protein with glutathione S-transferase (GST) in Spodoptera frugiperda (Sf) cells using the baculovirus expression vector (BEV) system. The protein is correctly produced and can be purified from crude whole-cell extracts by a single-step, batch-wise affinity-purification procedure. We show that this GST-hER fusion protein binds at its DNA-binding site specifically and in a hormone-inducible manner. Furthermore, we used the purified hER to analyze the complex estrogen response element (ERE) in the promoter of the oxytocin-encoding gene.
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PMID:A rapid one-step method to purify baculovirus-expressed human estrogen receptor to be used in the analysis of the oxytocin promoter. 807 33

Arginine vasopressin-immunoreactive (AVP-ir) neurons in the bed nucleus of stria terminalis (BST) and medial amygdaloid nucleus are very responsive to gonadal hormones. After gonadectomy, these neurons lose their AVP immunoreactivity and stop expressing AVP mRNA. Testosterone treatment reverses these changes, acting via androgen as well as estrogen receptor-mediated mechanisms. Although AVP-ir neurons contain estrogen receptor immunoreactivity, it is not known whether they also contain androgen receptor immunoreactivity. To answer this question, brains of male rats were stained immunocytochemically for AVP as well as for androgen receptors. In the BST and medial amygdaloid nucleus, respectively, 90.5% and 91.2% of the AVP-ir neurons contained androgen receptor immunoreactivity. In contrast, in the suprachiasmatic nucleus, the supraoptic nucleus, and the magnocellular portion of the paraventricular nucleus (PVN), none of the AVP-ir neurons contained androgen receptor immunoreactivity. In the ventral zone of the medial parvocellular part of the PVN (mpvPVN), 4.3% of the scattered AVP-ir neurons contained androgen receptor immunoreactivity. One of the control experiments, i.e. staining sections for oxytocin (OT) rather than AVP, revealed that although OT-ir neurons in the supraoptic and magnocellular portion of the PVN did not contain androgen receptor immunoreactivity, 52.5% of the OT-ir neurons in the mpvPVN did. The results suggest that androgens can bind to androgen receptors in AVP-ir neurons in the BST and medial amygdaloid nucleus, possibly to influence AVP expression. The results also suggest that androgens can bind to androgen receptors in AVP-ir and OT-ir neurons in the mpvPVN. The function of the latter interaction, however, is unclear.
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PMID:Distribution of androgen receptor immunoreactivity in vasopressin- and oxytocin-immunoreactive neurons in the male rat brain. 819 87

The orphan receptor chicken ovalbumin upstream promoter transcription factor I (COUP-TF I) fully prevented not only the activation of the oxytocin gene by retinoic acid and thyroid hormone but also completely repressed the estrogen-dependent stimulation in transfected P19 EC cells. DNase I footprinting showed that the COUP-TF I protein bound to the 5'-flanking region of the oxytocin gene at the site of the distal composite hormone response element, which mediates the responses to estrogen, retinoic acid, and thyroid hormone. Electrophoretic mobility shift assay using this composite hormone response element as probe showed that COUP-TF I and the estrogen receptor competed for binding but did not form a heterodimer. The binding by COUP-TF I was stronger than the binding of the estrogen receptor. Thus, the mechanism of repression involves occupancy of integrated binding sites. By mutagenesis of the composite hormone response element, the COUP-TF I binding site and the estrogen response element could be separated, resulting in functional dissociation of the repressive action of COUP-TF I and the induction by estrogen. The results show that repression of gene expression by COUP-TF I is not limited to receptors that act through heterodimerization but also extends to the homodimer-forming estrogen receptor in a context-dependent manner. This interaction between COUP-TF I and the estrogen receptor may provide a physiological mechanism of selective antagonism of gene regulation by estrogens.
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PMID:Repression of estrogen-dependent stimulation of the oxytocin gene by chicken ovalbumin upstream promoter transcription factor I. 819 42

The expression of the oxytocin (OT) receptor (OTR) in breast cancer was studied using newly established anti-OTR monoclonal antibodies. Immunoblotting indicated that the antibody 2F8 recognized a 70K OTR in the pregnant myometrium and breast cancer tissue. Among 57 breast cancer patients, we detected OTR immunoreactivity in 52 (91.2%) by immunohistochemistry using 2F8. Using another monoclonal antibody for different receptor domains, 1-2, the staining profile was identical in all positive samples. Of 52 OTR-positive samples, 28 were diffusely positive (> 80% of cancer cells were stained), and 24 were partially positive (< 80% cells were stained). The ratio of estrogen receptor-positive samples was slightly higher among those that were diffusely positive, but there was no apparent relationship between OTR expression and other clinical parameters. We also confirmed the expression of the OTR in positively stained samples by means of Northern blotting and RT-PCR at the transcription level. The OTR messenger RNA and RT-PCR product were the same size as those in the pregnant myometrium. We also determined the expression of the OTR using flow cytometry in four breast cancer cell lines (MCF-7, MDA-MB-231, MDA-MB-361, and MDA-MB-468). However, OT had no significant effect on their growth during a short period (7 days) of culture. These findings indicated that the OTR is expressed in breast cancer derived not from the myoepithelium but from the glandular or ductal epithelium; however, the biological function of OT in breast cancer remains to be determined.
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PMID:Investigation of the oxytocin receptor expression in human breast cancer tissue using newly established monoclonal antibodies. 859 29

Several studies in the past few years have supported the hypothesis that oxytocin (OT) is synthesized in a paracrine system within the pregnant human uterus and that this paracrine system may be an important regulator of the timing of human parturition. Using ribonuclease protection assays, we have demonstrated a three-fold increase in the rate of synthesis of OT mRNA in human decidua around the time of parturition. We also have shown that a similar increase in OT mRNA and peptide synthesis can be stimulated in vitro by physiological concentrations of estradiol. This increase is inhibited by concomitant use of the estrogen receptor (ER) blocker tamoxifen or by transcription inhibitors. Progesterone had little, if any effect. We also detected mRNAs for ER and progesterone receptor (PR) in amnion, chorion and decidua with the same relative tissue concentrations as OT mRNA. The concentrations of ER but not PR increased significantly around the time of labour onset. To determine if local OT concentrations may be regulated by changes in OT metabolism, we determined kinetic parameters for OT metabolism in decidua, chorion and placenta. [3H]tyrosyl-OT was used as substrate. Metabolites were separated using HPLC and identified using amino acid analysis and mass spectrometry. Metabolism in decidua and chorion occurred predominantly via a cytosolic post-proline endopeptidase and the activity was comparable to placenta. In microsomal fractions, cystine aminopeptidase activity predominated and placenta had significantly more activity than decidua and chorion. There were no changes in any Km or apparent vmax values around the time of parturition. These findings support the existence of a paracrine system within human decidua that involves sex steroids regulating synthesis of OT and that undergoes significant changes around the time of parturition. Changes in local OT concentrations are controlled by rates of synthesis rather than rates of metabolism.
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PMID:Synthesis and metabolism of oxytocin in late gestation in human decidua. 871 92

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that are associated with decreased gestation length in women as well as other mammals. Many lightly chlorinated PCBs are hydroxylated in vivo. The PCB congener 4-hydroxy-2',4',6'-trichlorobiphenyl (4-OH-TCB) has a high affinity for estrogen receptors and exerts a uterotropic effect in vivo. This study tested the hypothesis that 4-OH-TCB increases the contractile response of midgestation uteri to oxytocin by an estrogen receptor-mediated mechanism. After in vitro treatments with 4-OH-TCB or estradiol-17beta for 20 h or 42 h, uterine explants from midgestation rats were mounted in standard muscle baths for measurement of isometric contractions. A 20-h exposure to either 4-OH-TCB (0.1, 1, or 10 microM) or estradiol-17beta (10 nM) failed to alter the contractile response to cumulative additions of oxytocin (10(-10) to 10(-7) M). However, a 42-h exposure to either 1 microM 4-OH-TCB or 10 nM estradiol-17beta significantly elevated the contractile response to oxytocin, which was abolished by cotreatment with the estrogen receptor antagonist tamoxifen (30 nM). These data support the hypothesis that the stimulatory actions of estradiol-17beta and 4-OH-TCB on oxytocin-induced oscillatory contractions are mediated by estrogen receptors. Under the conditions of this experiment, more than 20 h of treatment is required to elicit the estrogen-dependent responses.
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PMID:Increase of oxytocin-induced oscillatory contractions by 4-hydroxy-2',4',6'-trichlorobiphenyl is estrogen receptor mediated. 911 32

Circulating estrogens influence the electrical and biosynthetic activity of the hypothalamic magnocellular neurons which synthesize vasopressin or oxytocin and regulate body fluid homeostasis and reproduction. As none of these magnocellular neurons express nuclear estrogen receptor in the rat, the present study has combined estrogen receptor immunocytochemistry with retrograde tracing techniques to examine whether the first-order neurons projecting to magnocellular neurons in the supraoptic nucleus may be receptive to estrogen. Green fluorescent latex microspheres (50 nl) were injected into the supraoptic nucleus of five ovariectomized rats. The largest numbers of retrogradely-labelled cells expressing estrogen receptor immunoreactivity were detected in the organum vasculosum of the lamina terminalis, anteroventral periventricular nucleus and medial preoptic nucleus where approximately 15% of all retrogradely-labelled cells were estrogen receptor-immunoreactive. Other prominent sites where double-labelled cells were detected were the median preoptic nucleus, subfornical organ, ventrolateral division of the hypothalamic ventromedial nucleus and the brainstem nucleus tractus solitarii. Triple labelling experiments in the caudal medulla revealed that the estrogen-receptive neurons of the nucleus tractus solitarii and ventrolateral medulla projecting to the supraoptic nucleus were not noradrenergic. These findings show that sub-populations of neurons projecting to the supraoptic nucleus express estrogen receptors. This provides immunocytochemical evidence that estrogen may regulate the activity of magnocellular oxytocin and vasopressin neurons in an indirect, trans-synaptic manner by influencing the activity of first-order neurons projecting to the supraoptic nucleus. The predominance of estrogen-receptive lamina terminalis and preoptic area inputs to the supraoptic nucleus suggests respective sites of estrogen action on magnocellular neurons in modulating fluid balance and reproductive function.
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PMID:Identification of estrogen receptor-containing neurons projecting to the rat supraoptic nucleus. 913 2

Oxytocin (OT) and its receptor (OTR) are synthesized in the endometrium and myometrium of the pregnant rat during late gestation. Both are regulated by estrogen and progesterone (P4), and tissue concentrations of both increase markedly before parturition. The P4 antagonist RU486 will induce parturition in the rat. The purpose of the present studies was to investigate changes in OT and OTR messenger RNA (mRNA) and peptide synthesis within the pregnant rat uterus during RU486-induced parturition. Pregnant rats were given a single injection of RU486 (2.5 mg/rat in oil) on day 15 of pregnancy (normal delivery occurs on day 22). Control animals received injections of oil only. Groups of animals (n = 5 in each group) were euthanized at 0, 6, 12, 24, and 48 h after injection and during labor (immediately after delivery of the first pup). Maternal serum estradiol (E2), P4 and uterine OT, and PGE2 concentrations were measured by RIA. Prostaglandin F2alpha and estrogen receptor levels were measured by enzyme immunoassay (EIA). OTR and P4 receptor (PR) were measured using radioligand-binding assays. OT, OTR, and estrogen receptor mRNAs were measured with ribonuclease protection assays. The average time to delivery, after RU486 injection, was 27.0 +/- 1.2 h. Serum E2 and P4 levels were increased slightly, but significantly, at 24 h after RU486. In controls, OT mRNA increased significantly, and this increase was blocked in the RU486 treatment group. OTR mRNA levels increased within 6 h of RU486 and remained elevated until delivery. OTR peptide was increased by 12 h. PGE2 and PGF2alpha were increased 3-fold and 16-fold, respectively, but not until after the increase in OTR had occurred. We conclude that the mechanism of action of RU486 is to inhibit the P4 suppression of OTR synthesis, allowing increased expression of OTR, which may directly stimulate myometrial contractions or act indirectly through increased synthesis of PGs.
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PMID:Effects of RU486 on estrogen, progesterone, oxytocin, and their receptors in the rat uterus during late gestation. 920 15

Concentrations of oxytocin (OT) peptide increase in rat uterine tissues at the time of parturition. We have measured the rate of OT metabolism in these tissues in late gestation to determine whether a decrease in OT catabolism is responsible for the increase in OT concentrations. Uterine and placental tissues were obtained from groups of rats at Days 16, 19, 21, 21.5, 22, and after delivery of the first pup. Delivery usually occurs in the early afternoon of Day 22. Some animals were treated with the estrogen receptor blocker tamoxifen, which will delay parturition by approximately 24 h. Cytosolic and microsomal preparations obtained using ultracentrifugation were incubated with radiolabeled OT. Metabolites were separated using HPLC, and enzyme kinetic parameters were calculated. OT was actively metabolized in both uterine and placental tissues. Total oxytocinase activity was similar in the two tissues. In uterine tissues, activity was greater in the cytosolic fractions. In placenta, activity was evenly distributed between the cytosolic and microsomal fractions. The cytosolic fractions of each tissue contained predominantly post-proline endopeptidase activity, whereas the microsomes contained predominantly aminopeptidase activity. There was a slight trend to decreasing oxytocinase activity with advancing gestation in both subcellular fractions, but this was statistically significant only in the microsomal fraction. The maximal decline in activity was only 25-50%. Tamoxifen treatment had no effect on oxytocinase activity. We conclude that rat uterine and placental tissues contain post-proline endopeptidase and aminopeptidase activities that metabolize OT. It is doubtful that changes in these activities are major factors in regulating the increase in OT concentrations measured in rat intrauterine tissues at the time of parturition.
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PMID:Metabolism of oxytocin in rat uterus and placenta in late gestation. 931 84

An alternatively spliced mRNA coding for a variant estrogen receptor (ER) missing exon 4 (ERdelta4) was detected in the breast tumor cell line MCF7 and meningioma tissue by using the reversed transcriptase PCR technique. The trans-activational properties of this mutant ER were assessed in embryo carcinoma P19EC and human choriocarcinoma JEG3 cells by co-transfection of the ERdelta4 expression vector with an oxytocin promoter construct containing an estrogen-responsive element. ERdelta4 did not trans-activate the oxytocin promoter in either a hormone-dependent or -independent manner. Co-transfection of ERdelta4 together with the wtER did not show any interference of ERdelta4 on the stimulation of the oxytocin promoter by the wtER. ERdelta4 was translated in vitro. Its capacity to bind estradiol, and the binding of the variant to a synthetic estrogen-responsive element were compared to those of the wild-type receptor. ERdelta4 did not bind to a synthetic estrogen-responsive element, nor did it bind estradiol. Hence, ERdelta4 appears to be a silent variant and we speculate that it is without any role in tumor progression.
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PMID:Functional analysis of an alternatively spliced estrogen receptor lacking exon 4 isolated from MCF-7 breast cancer cells and meningioma tissue. 939 58


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