Heterogeneity of steroid hormone receptor in adult rat lung cytosol

Chromatography on cellulose DEAE-52 columns revealed that the glucocorticoid receptor from rat lung cytosol consisted of a component in the 0.001 M prewash, revealed with synthetic steroids and natural mineralocorticoids, a second component eluted with 0.04 M PO₄, labelled with triamcinolone, dexamethasone, and a third moiety in the 0.06 M PO₄ region, evident with natural glucocorticoids (corticosterone, cortisol) as well as mineralocorticoids (aldosterone, deoxycorticosterone). The thrid component coelutedf with rat blood serum transcortin in double labelled experiments. Rat lung was devoid of another component in the 0.02 M PO₄ found in rat liver supernate and of the mineralocorticoid receptor evident only in rat kidney. Chromatography on Sephadex G-200 columns revealed a shift of radioactivity from a higher to a lower molecular weight region in the presence of 0.4 M KCl. Collectively, these studies indicate the subunit nature of the lung receptor as evidenced in most tissues hitherto tested. Moreover, polymorphism within a given subunit component can not be revealed by competition alone, as attempted by others, but can be revealed under selected conditions of physical separation.     

The steroid hormone levels and receptors of steroid hormone receptors in rat muscles during physical exertion

It is shown that the testosterone content in skeletal muscles of female albino rats is 2-fold decreased, while the estradiol content-1.5-fold increased and progesteron content showed no changes after systematic physical exercises. The pharmacokinetic investigations showed that androgen half-life in the organism decreased from 8 to 5 h under physical exercises. The amount of androgen receptors in cytosol of skeletal muscles increases from 1.34 +/- 0.08 to 1.71 +/- 0.10 fmol/mg per 1 mg of protein. Kd is 0.40 +/- 0.03 and 0.48 +/- 0.08 nM, respectively. Sensitivity of the organism to hormonal signal play an important role in the metabolism regulation in skeletal muscles along with the hormonal content change during the organism adaptation to physical exercises.     

Estradiol and a selective estrogen receptor modulator affect steroid hormone receptor messenger RNA levels and turnover in explant cultures of sheep endometrium

Estrogens upregulate estrogen receptor (ER) and progesterone receptor (PR) gene expression in endometrium immediately before ovulation to prepare it for nurturing embryos. Most in vitro model systems have lost the ability to upregulate expression of the ER gene in response to estradiol (E2) or the ability to express the ER gene at all. Here, we used explant cultures from control and E2-treated ewes and assessed expression of four genes (ER, PR, glyceraldehyde 3-phosphate dehydrogenase [GAPDH], and cyclophilin [CYC] genes) that are upregulated by E2 in vivo on Northern blots. In cultures from control and E2-treated ewes, ER and PR messenger ribonucleic acid (mRNA) levels dropped significantly during 24 h of culture in the absence of E2. Glyceraldehyde 3-phosphate dehydrogenase mRNA levels increased 300% in explants from control ewes to match the higher levels in the endometrium of the E2-treated ewe (in vivo and in explant culture). The only effect of E2 in the explant cultures was to prevent the decrease in PR mRNA. The new selective ER modulator, EM-800 (EM), decreased ER and PR mRNA levels in explants from control ewes but upregulated GAPDH and CYC mRNA levels. The EM treatment in vitro mimicked that of E2 by increasing the half-life of ER mRNA in endometrial explants. These data illustrate distinct, gene-specific effects of the explant culture process, E2, and EM on the expression of endometrial genes.     

Uterine and placental growth: RNA and protein metabolism and steroid hormone receptor levels in the endometrium, whole uterus and cotyledons during pregnancy in the ewe

Some aspects of uterine and placental growth have been examine during pregnancy in the ewe. Changes in vitro rates of protein synthesis, RNA: DNA and protein: DNA ratios and the tissue concentration of DNA in intercaruncular endometrium and caruncles (cotyledons between days 0 (oestrus) and 112 of pregnancy were compared with corresponding changes in the concentrations of high-affinity cytosol receptors for oestradiol and progesterone in whole uterus and caruncles/maternal cotyledons. Rapid growth of the intercaruncular endometrium between days 28 and 112 and of the developing cotyledons between days 28 and 84 occur in the presence of tissue levels of both steroid receptors that are extremely low in relation to the corresponding levels seen in the uterus at oestrus. If uterine responses to steroid hormones are regulated by the amounts of specific receptors present in the tissue, the results support the concept that uterine growth after day 28 of pregnancy results primarily from the physical stimulus of the growing concepts rather than from the actions of endogenous steroid sex hormones.     

Ultrastructure of the porcine myometrium during pregnancy

The fine structure of myometrium from pigs collected at well-defined stages during pregnancy was investigated by transmission electron microscopy. The morphology of the pregnant myometrium resembled that in non-pregnant pigs. Thick myofilaments were conspicuous during early pregnancy, inapparent during mid-pregnancy and visible again by days 80-84 and towards parturition. Gap junctions were extremely rare throughout pregnancy. Only occasionally were nerve axons observed.     

Maternal corticotropin-releasing hormone levels during pregnancy and offspring adiposity

Objective: Animal models suggest that fetal exposure to glucocorticoids can program adiposity, especially central adiposity, later in life. We examined associations of maternal corticotropin‐releasing hormone (CRH) levels in the late 2nd trimester of pregnancy, a marker of fetal glucocorticoid exposure, with child adiposity at age 3 years. Research Methods and Procedures: We analyzed data from 199 participants in Project Viva, a prospective cohort study of pregnant women and their children, At age 3 years, the main outcomes were age‐sex‐specific BMI z score and the sum of subscapular (SS) and triceps (TR) skinfold thicknesses to represent overall adiposity, and ratio of SS to TR (SS:TR) to represent central adiposity. Results: Mean (standard deviation) maternal 2nd trimester log CRH was 4.94 (0.56) pg/mL. At age 3, mean (standard deviation) for BMI z score was 0.52 (1.02); for SS + TR, 16.51 (3.94) mm; and for SS:TR, 0.67 (0.17). Log CRH was mildly inversely correlated with birth weight (r = ?0.08), chiefly because of its association with length of gestation (r = ?0.21) rather than fetal growth (r = ?0.004). After adjustment for sociodemographic factors, maternal smoking, BMI, and gestational weight gain, fetal growth, length of gestation, breastfeeding duration, and (for SS:TR only) child's 3‐year BMI, each increment of 1 unit of log CRH was associated with a reduction in BMI z score [?0.43; 95% confidence interval (CI), ?0.73, ?0.14; p = 0.004] and possible reduction in SS + TR (?1.10; 95% CI, ?2.33, 0.14; p = 0.08). In contrast, log CRH was associated with higher SS:TR (0.07; 95% CI, 0.02, 0.13; p = 0.007). Discussion: Fetal exposure to glucocorticoids, although associated with an overall decrease in body size, may cause an increase in central adiposity.     

Ovarian steroid production in rats treated with gonadotropin-releasing hormone during early pregnancy

In the pregnant rat, luteinizing hormone (LH) stimulates the ovarian production of testosterone (T) which is aromatized to estradiol (E2). E2 promotes progesterone (P) synthesis by the ovary. To determine if the administration of gonadotropin-releasing hormone (GnRH) disrupts pregnancy by suppressing ovarian steroid production, rats were treated on days 7-12 of pregnancy with 25, 50 or 100 micrograms/day of GnRH or 0.2, 1 or 5 micrograms/day of a GnRH agonist (GnRH-Ag). The higher two doses of GnRH or GnRH-Ag within 24 h suppressed peripheral levels of plasma P and terminated pregnancy within 48 h. By day 12, P levels in the ovarian vein in rats treated with GnRH or GnRH-Ag in respective doses were 2098 +/- 261, 732 +/- 437, 110 +/- 15, and 2575 +/- 463, 49 +/- 9, 43 +/- 8 compared to 1833 +/- 433 ng/ml in controls. Daily treatment of P (4 mg) and E2 (0.5 microgram) simultaneously with GnRH-Ag at its maximum dose reversed the abortifacient effect of GnRH-Ag and maintained pregnancy. Peripheral levels of Plasma LH in all groups were higher than controls on days 10 and 12. Ovarian vein levels of T on days 10 or 12 of pregnancy were either not significantly different from controls (at 2703 +/- 607 or 3249 +/- 690 pg/ml, respectively) or increased dramatically to 9547 +/- 1769 on day 10 and to 5985 +/- 1426 pg/ml on day 12 in rats treated with 0.2 microgram of GnRH-Ag. Similarly, ovarian vein levels of E2 on days 10 or 12 were either not significantly different from controls (at 2022 +/- 227 or 2793 +/- 184 pg/ml, respectively) or increased dramatically to 2980 +/- 58 pg/ml on day 10 in rats treated with 25 micrograms of GnRH or to 3296 +/- 241 on day 10 and to 3420 +/- 325 pg/ml on day 12 in rats treated with 0.2 microgram of GnRH-Ag. These results indicate that the abortifacient effect of GnRH administration in rats is not due to its effect on the uterus, but to its suppressive effects on ovarian P secretion. There was no evidence to show that a GnRH-induced fall in ovarian secretion of either T or E2 were involved in this process.     

文昌鱼核性类固醇激素受体信号研究进展

核性类固醇激素受体属核受体超家族成员,是配体依赖转录因子,在脊椎动物和无脊椎动物生殖内分泌中起关键作用。本文介绍了文昌鱼核性类固醇激素受体的结构、信号转导以及配体与受体结合的作用机制。同时,本综述将可为核性类固醇受体的进化研究提供新的资料。     

Attenuation of corticotropin-releasing hormone and arginine vasopressin responsiveness during late-gestation pregnancy in sheep

Responsiveness of the hypothalamo-pituitary-adrenal axis is decreased during pregnancy. Therefore, the objective of the present study was to determine if responsiveness at the level of individual corticotrophs to corticotropin-releasing hormone (CRH) or arginine vasopressin (AVP) is decreased during pregnancy in sheep. Anterior pituitaries (APs) were collected from pregnant and nonpregnant ewes. Half of the APs were dispersed, and cells were placed on immobilon and treated with vehicle, CRH (10 nM), or AVP (100 nM) for 2 h. Cells were then fixed and incubated with ACTH or pro-opiomelanocortin (POMC) antibodies. The percentage of cells staining positive for immunoreactive (ir) ACTH or POMC, the percentage of cells secreting irACTH or POMC, and the area of irACTH or POMC secretion were measured. RNA was extracted from the other half of the APs to quantify CRH type 1 (CRH-R1) and vasopressin type 1b (V1b) receptor mRNA by ribonuclease protection assay. CRH treatment increased the percentage of corticotrophs with relatively large areas of irACTH and POMC secretion in nonpregnant, but not in pregnant, ewes. AVP treatment significantly increased the percentage of irACTH- and POMC-secreting cells in nonpregnant, but not in pregnant, ewes. V1b receptor mRNA, but not CRH-R1 receptor mRNA, was significantly decreased during pregnancy. These results suggest that corticotroph responsiveness to CRH and AVP is decreased during pregnancy in sheep. Therefore, reduced corticotroph responsiveness may contribute to stress hyporesponsivity during pregnancy.     

Maternal hormone levels during Na 872 infusion in late pregnancy

In order to assess the effects of Na 872 infusion on maternal endocrinology during late pregnancy, we measured serum estradiol, estriol, progesterone, human placental lactogen, follicle simulating hormone, prolactin, cyclic adenosine monophosphate, cortisol and insulin before, during and after Na 872 infusion (bromhexine 2 mg/min for one hour) in ten mothers. As compared to six control mothers, no changes could be observed. This suggests that the claimed maturing effect of Na 872 on the fetal lungs is not mediated by the hormonal changes measurable in maternal blood.     

Electrical coupling in rat myometrium during pregnancy.

Gap junctions were found in rat myometrium only during parturition of abortion. A comparison was made between the values of the length constants obtained from longitudinally cut strips of rat myometrium at the midterm stage of pregnancy and during parturition. No significant difference was found between these values. No significant difference was found between length constants measured in myometrium from rats near term (22 days) and those during parturition, or between midterm myometrium and myometrium taken from animals aborting at midterm following ovariectomy. It was concluded that the appearance of gap junctions in parturient myometrium does not alter the spread of passive current in the longitudinal axis of the cells in these tissues. It is suggested that gap junctions are not required for spread of passive current, and that other structures may provide an alternate path.     

Nuclear origin of progesterone receptor of the chick oviduct cytosol

Summary Progesterone receptor (PR) was studied immunoelectron microscopically from fixed vibratome sections of the chick oviduct and biochemically from the fractionated oviduct homogenate. Immunoelectron microscopically both unoccupied and occupied PR were localized inside the nuclei. Only a few cells showed PR immunoreactivity in the endoplasmic reticulum which probably represents newly synthetized PR. Biochemically unoccupied PR was in the cytosol fraction. The cytosol and nuclear PR as well as the non-transformed 8S-form and the transformed 4S-forms of cytosol PR were recognized by the anti-PR antibody (IgG-RB). The lack of PR immunostaining in the cytoplasm is therefore not due to lack of recognition by IgG-RB. We propose that in the chick oviduct progesterone receptor is a nuclear protein but synthetized in the endoplasmic reticulum.     

Changes in CD38 expression and ADP-ribosyl cyclase activity in rat myometrium during pregnancy: influence of sex steroid hormones

Cyclic ADP-ribose (cADPR), synthesized by CD38, regulates intracellular calcium in uterine smooth muscle. CD38 is a transmembrane protein that has both ADP-ribosyl cyclase and cADPR hydrolase enzyme activities involved in cADPR metabolism. CD38 expression and its enzyme activities in uterine smooth muscle are regulated by estrogen. In the present study, we examined CD38 expression, its enzyme activities, and cADPR levels in myometrium obtained from rats at 14-17 days of gestation (preterm) and at parturition (term). CD38 expression, ADP-ribosyl cyclase activity, and cADPR levels were higher in uterine tissues obtained from term rats compared with that of preterm rats, while activity of cADPR hydrolase did not significantly change. In an effort to address whether changes in estrogen: progesterone ratio that occur during pregnancy account for the observed effects on CD38 expression and function, we determined the effect of different doses of progesterone in the presence of estrogen on CD38 expression and its enzyme activities in uterine smooth muscle obtained from ovariectomized rats. In myometrium obtained from ovariectomized rats, estrogen administration caused increased CD38 protein expression and ADP-ribosyl cyclase activity. The estrogen-induced increases in CD38 expression and ADP-ribosyl cyclase activity were inhibited by simultaneous administration of 10 or 20 mg of progesterone. These results indicate that the estrogen:progesterone ratio determines CD38 expression and ADP-ribosyl cyclase activity. These changes in CD38/cADPR pathway may contribute to increased uterine motility and onset of labor.     

Tissue- and gene-specific recruitment of steroid receptor coactivator-3 by thyroid hormone receptor during development

Numerous coactivators that bind nuclear hormone receptors have been isolated and characterized in vitro. Relatively few studies have addressed the developmental roles of these cofactors in vivo. By using the total dependence of amphibian metamorphosis on thyroid hormone (T3) as a model, we have investigated the role of steroid receptor coactivator 3 (SRC3) in gene activation by thyroid hormone receptor (TR) in vivo. First, expression analysis showed that SRC3 was expressed in all tadpole organs analyzed. In addition, during natural as well as T3-induced metamorphosis, SRC3 was up-regulated in both the tail and intestine, two organs that undergo extensive transformations during metamorphosis and the focus of the current study. We then performed chromatin immunoprecipitation assays to investigate whether SRC3 is recruited to endogenous T3 target genes in vivo in developing tadpoles. Surprisingly, we found that SRC3 was recruited in a gene- and tissue-dependent manner to target genes by TR, both upon T3 treatment of premetamorphic tadpoles and during natural metamorphosis. In particular, in the tail, SRC3 was not recruited in a T3-dependent manner to the target TRbetaA promoter, suggesting either no recruitment or constitutive association. Finally, by using transgenic tadpoles expressing a dominant negative SRC3 (F-dnSRC3), we demonstrated that F-dnSRC3 was recruited in a T3-dependent manner in both the intestine and tail, blocking the recruitment of endogenous coactivators and histone acetylation. These results suggest that SRC3 is utilized in a gene- and tissue-specific manner by TR during development.