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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Estradiol binding components in the cytosol and nuclear fractions of the ovary from immature rats (22-28 days old) were characterized by in vitro methods. Several of the biochemical characteristics of the estradiol binding components in the ovarian tissue were compared with the estradiol receptor from the uterus. The results suggest that the ovarian estradiol binding components are similar to the specific high affinity estradiol receptors in the uterus. In the cytosol of intact rat ovary a significant fraction of the total binding sites was found to be occupied, presumably by the endogenous estrogen. Following hypophysectomy there was a significant increase in the available cytosol binding sites. Evidence for translocation of cytosol receptor-estrogen (RE) complex to the nucleus was obtained for the ovary. The sedimentation properties of the RE complex of the ovary and the uterus are similar. The ovarian cytosol RE complex sediments at 7-8S in glycerol gradients at low ionic strength and at 4S in sucrose gradients at high ionic strength. Following extraction with 0.4 M KCl the ovarain nuclear RE complex sediments at 5S in sucrose gradients which is identical to that of the uterine nuclear receptor.
Steroids 1977 Feb
PMID:Estradiol-17beta receptors in the immature rat ovary. 84 22

In the immature rat uterus, high concentrations of androgens competed specifically with estradiol on the estrogen receptor (RE). This competition was stereospecific for C19 steroids bearing a 17beta and/or 3 hydroxyl group. Very low affinity ligands, such as testosterone, could not compete with estradiol at equilibrium but decreased the association rate of estradiol on its receptor. High doses (greater than 0.4mg) of 5dihydrotestosterone provoked in vivo as in vitro the nuclear translocation of RE. The nuclear receptor thus formed displayed the same 5.2 S sedimentation constant as that induced by estradiol. We conclude that the weak affinity binding of androgens to the estrogen receptor is sufficient to induce its nuclear translocation in vivo provided androgen concentration is high enough in uterus to occupy the estradiol binding site. Conversely, progesterone which does not bind RE could not provoke its nuclear translocation.
Steroids 1976 Oct
PMID:Androgen on the estrogen receptor. I - Binding and in vivo nuclear translocation. 100 24

Incubations of p-nitrophenyl fatty acyl esters and estradiol-17 beta fatty acyl 17-esters with porcine esterase, human mammary tumor cytosol and rat uterine cytosol leads to ester hydrolysis of compounds with short chain fatty acids. Esters with long chain fatty acids show no hydrolysis except in the presence of Tween 80. Short chain fatty acid esters have a higher binding potency to the estrogen receptor than long chain fatty acid esters. Extraction of the nuclear receptor peak sedimenting at 4.6S and identification of the steroid showed that about 90% of the radioactivity was associated with estradiol and only 10% with estradiol esters. These studies show that estradiol fatty acyl esters act as a storage form from which estradiol is released by enzymatic hydrolysis.
Steroids 1983 Oct
PMID:Significance of lipoidal estradiol in human mammary tumors. 667 46

We have investigated the action of high doses of androgens in Gobius niger L., a marine teleostean fish, by characterizing specific steroid receptors in liver and by assaying the plasma vitellogenin concentration under different hormonal treatments. Estrogen and androgen receptors were characterized in the liver nuclear extracts according to their binding specificity. The maximum binding capacity was 25 fmoles/mg protein for the estrogen and androgen receptors. In vivo, high doses of DHT()increased the concentration of plasmatic vitellogenin as assayed by immunodiffusion while low doses were inefficient. In spite of a similar number of estrogen and androgen nuclear receptor sites (25 fmoles/mg protein), DHT was at least 70 fold less active than E2 on yolk protein and vitellogenin induction both in male and female Gobius niger. In addition, the antiestrogen tamoxifen, which was inactive by itself, inhibited the E2 and the DHT induced accumulation of vitellogenin. Progesterone (2 mg/fish) was also totally inactive in inducing vitellogenin. We conclude that the induction of vitellogenin by DHT is mediated by the estrogen receptor rather than by the androgen receptor. In addition to the estradiol induced protein in rat uterus and to other estrogenic responses obtained by androgens in mammary cancer, fish vitellogenin is another estrogen regulated protein which can be induced by high doses of androgens.
Steroids 1980 Mar
PMID:Effect of androgen mediated by the estrogen receptor of fish liver: vitellogenin accumulation. 676 82

We have examined the specific binding of estradiol (E2) and estrone (E1) within MCF-7 cells using both cytosol and whole cell suspension binding assay techniques. The results of these studies have revealed that each of these estrogens binds the high but different affinity to the same single class of cytosol receptor (ER). The incubation of intact cells with E2 at 37 degrees resulted in the rapid formation, nuclear binding, and nuclear processing of E2-ER complexes. Reduction of incubation temperature to 15 degrees C and 4 degrees C resulted in slowed but continued E2-ER formation and nuclear binding, and in a marked inhibition of nuclear receptor processing. The incubation of intact cells with E1 at 37 degrees also was associated with the formation, nuclear binding, and nuclear processing of estrogen-ER complexes. Interestingly, however, E2 rather the E1 represented the major species of specifically bound estrogen under these conditions. This observation suggests that the estrogenic action of E1 in MCF-7 cells may be mediated largely by the intracellular formation of E2. This phenomenon provides a likely explanation of the unexpected potency of E1 in this system previously observed by other workers. Furthermore, our results suggest that E1 may represent a major source of estrogenic stimulation for some hormone-dependent human breast tumors.
Steroids 1982 Mar
PMID:The specific binding of estradiol and estrone and the subsequent distribution of estrogen-receptor complexes within MCF-7 human breast cancer cells. 709 23

Total androgen receptor content of ventral or dorsolateral prostate of intact, aged (730-740 day old) rats is decreased 50% when compared to intact, young mature (150-170 day old) rats. Treatment with exogenous testosterone increased ventral and dorsolateral prostate androgen receptor content per cell in aged rats to values identical to those of prostates of young mature rats. The increase in prostate receptor content was not attributable to testosterone mediated cellular hypertrophy or hyperplasia. At 24 hr post-orchiectomy ventral prostate cytoplasmic androgen receptors are depleted of endogenous androgen, without any decrease in number of receptors per cell, and nuclear androgen receptors are undetectable. During 30 to 60 min after a single 200 microgram testosterone injection, ventral prostate nuclear receptor content increased to the level of intact control rats without producing any reduction in total cytoplasmic androgen receptor content. Although dorsolateral prostate is devoid of cytoplasmic androgen receptor, the effects of orchiectomy and testosterone treatment upon nuclear androgen receptor are comparable to those seen in ventral prostate. These effects of orchiectomy and testosterone injection upon prostatic receptor content and distribution were identical in prostates of young and aged rats. Our studies show that receptor processing in prostates of young and aged rats does not involve a process by which nuclear receptor is derived by depletion of cytoplasmic receptor. Moreover, our studies of the effect of short-term (48 hr) exogenous testosterone treatment upon androgen receptor content in prostates of aged rats are the first demonstration that androgen receptor content may be enhanced independent of generalized androgen mediated anabolic effects in prostate.
Steroids 1980 Feb
PMID:Androgen regulation of androgen receptor content and distribution in the ventral and dorsolateral prostates of aging AXC rats. 737 16

The mineralocorticoid and glucocorticoid receptors (MR and GR, respectively) are closely related members of the nuclear receptor superfamily. Despite marked functional similarities and a high degree of sequence conservation between MR and GR, the mineralocorticoid and glucocorticoid hormones elicit markedly different physiological effects, even in cells expressing both receptors. Hormone specificity is, in part, determined by the actions of 11 beta-hydroxysteroid dehydrogenase. However, other mechanisms must obtain in cells that express both receptors and respond differentially to the two classes of hormone. Indeed, MR and GR, while functionally redundant in some contexts, in others display distinct transcriptional specificities. In particular, in the presence of members of the AP1 family of regulatory factors, cJun and cFos, a composite response element, plfG, is GR-specific. Transcription from a plfG-linked gene is stimulated by GR in the presence of cJun and repressed by GR in the presence of cJun and cFos. MR neither stimulates nor represses transcription in the same contexts, thus indicating that receptor transcriptional specificities can be distinguished by differential interactions with nonreceptor factors at a composite response element. The implications of these findings for mineralocorticoid and glucocorticoid hormone specificity in various tissues are discussed.
Steroids 1994 Feb
PMID:A mechanistic basis for distinct mineralocorticoid and glucocorticoid receptor transcriptional specificities. 819 46

Because progesterone suppresses myometrial contractility, the assumption is often made that the withdrawal of this steroid is a prerequisite for parturition. However, steroid patterns in maternal blood of the guinea pig do not consistently change with impending parturition and it has been claimed that progesterone does not suppress guinea pig myometrial contraction. The present study investigated progesterone and estrogen nuclear receptor binding in myometrium, endometrium, and chorion between 32 days of gestation and delivery at 67-71 days. Binding characteristics and behavior during sedimentation in sucrose density gradients were typical of the steroid hormone receptor family. Decreased progestin binding occurred in the myometrium, from a high of 1600 fmol/mg DNA at 49-51 days to a low of 450 fmol/mg DNA (P < 0.01) on the day of detectable pubic relaxation. This decrease commenced at 60-63 days just before the onset of relaxation. A similar, though less well defined change occurred in endometrium. Estradiol nuclear receptor binding in myometrium remained at about 350 fmol/mg DNA from 32 days until 1-2 days pre-partum when it increased to about 650 fmol/mg DNA (P < 0.05). Estradiol binding in endometrium showed an inconsistent pattern and chorion binding for both progestin and estradiol was low and unremarkable. We conclude that there is a potential for decreased progesterone effect in myometrium at about one week before delivery and increased estrogen action in that tissue immediately before delivery.
Steroids 1993 Oct
PMID:Nuclear receptors for progesterone and estradiol in the guinea pig uterine compartment during gestation. 825 58

Steroids and thyroid hormones, as well as vitamin D, retinoids and some nutrient metabolites (fatty acids, prostaglandins, farnesol metabolites) act by binding to members of the zinc-finger containing superfamily of nuclear hormone receptors. These receptor proteins bind directly to specific DNA recognition sequences (hormone response elements) in the promoter region of target genes, resulting in the alteration of the transcription initiation rate. While the principle of action of these receptors appears to be quite simple, the promiscuous behavior of some members of this family as well as cross-talk with other signaling systems result in an intricate regulatory network with distinct particularities for each receptor type. Specific areas of current interest in nuclear receptor research are: (i) the mechanisms for target gene specificity, which occur at the level of receptor expression, ligand metabolism and/or DNA sequence; (ii) cross-talk with other signaling systems resulting in the modulation of the transcriptional activity of the ligand-activated receptor through phosphorylation and/or heterodimerization with shared nuclear factors; and (iii) the discovery of novel agonistic and antagonistic ligands for established and orphan nuclear receptors. Recent insights through screening strategies for putative ligands, the cloning of co-activator proteins, as well as the characterization of human and animal models with germline and somatic mutations in nuclear receptors have resulted in important insights into some of the above questions, which are fundamental for a better understanding of the role of these hormone-activated transcription factors during development and cell differentiation.
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PMID:Regulation of gene expression by nuclear hormone receptors. 902 99

In the 24 hours before ovulation, there is an abrupt decline in the ability of theca cells from the largest chicken preovulatory follicle to produce androstenedione from all substrates except dehydroepiandrosterone. In this study, we tested the hypothesis that progesterone from granulosa cells might inhibit andostenedione production by the adjacent theca cells. Physiological concentrations of progesterone inhibited andostenedione production by dispersed thecal cells from the substrate 17 alpha-hydroxyprogesterone but not dehydroepiandrosterone in both a dose- and time-dependent manner. In contrast, the metabolites of progesterone, 17 alpha-hydroxyprogesterone, and androstenedione at a high concentration (100 nM) failed to produce such an inhibitory effect. In addition, this inhibitory effect of progesterone was reversed by the protein synthesis inhibitor cycloheximide. The results of this study seem to suggest that progesterone acts indirectly through its nuclear receptor to induce the synthesis of a protein that possibly inhibits C17,20 lyase activity and/or C17,20 lyase gene expression.
Steroids 1997 Feb
PMID:The inhibition of androstenedione production in mature thecal cells from the ovary of the domestic hen (Gallus domesticus): evidence for the involvement of progestins. 905 79


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