Hormonal regulation and characterisation of the aldehyde oxidase-like gene of hamster Harderian gland

The HG is a compound tubulo-alveolar gland located in the orbital cavity of the majority of vertebrates. In the golden hamster it shows a clear cut sexual dimorphism in both morphological and biochemical parameters such as cell types, protein pattern, lipid metabolism, porphyrin content, steroid hormone receptor expression. In a previous study we found that in primary culture of male hamster Harderian gland (HG), androgens (A) increase the MHG07 (male Harderian gland) expression and this effect is abrogated by both flutamide and cycloheximide. The present study represents a deeper analysis on MHG07 regulation by other members of steroid/thyroid hormone superfamily. Estrogens (E) impair the stimulatory effect of A and after the addition of a pure anti-estrogen, ICI 164,384, the negative effect of E is abrogated. Dexamethasone (Dex), used alone or in combination with A negatively affect the MHG07 expression. Also T(3) increases the expression of MHG07 mRNA. Progesterone (P) does not affect the expression of MHG07 mRNA. The use of cycloheximide abrogates the effect of steroids, suggesting that the latter act through their own receptors. Dose-response experiments show that low steroid concentrations (10(-12)M) are sufficient to affect the MHG07 expression. It is argued that the expression of MHG07 is under a highly coordinate relationship between androgen, estrogen, glucocorticoid, retinoic acid and thyroid hormones.     

The pituitary function of androgen receptor constitutes a glucocorticoid production circuit

Androgen receptor (AR) mediates diverse androgen actions, particularly reproductive processes in males and females. AR-mediated androgen signaling is considered to also control metabolic processes; however, the molecular basis remains elusive. In the present study, we explored the molecular mechanism of late-onset obesity in male AR null mutant (ARKO) mice. We determined that the obesity was caused by a hypercorticoid state. The negative feedback system regulating glucocorticoid production was impaired in ARKO mice. Male and female ARKO mice exhibited hypertrophic adrenal glands and glucocorticoid overproduction, presumably due to high levels of adrenal corticotropic hormone. The pituitary glands of the ARKO males had increased expression of proopiomelanocortin and decreased expression of the glucocorticoid receptor (GR). There were no overt structural abnormalities and no alteration in the distribution of cell types in the pituitaries of male ARKO mice. Additionally, there was normal production of the other hormones within the glucocorticoid feedback system in both the pituitary and hypothalamus. In a cell line derived from pituitary glands, GR expression was under the positive control of the activated AR. Thus, this study suggests that the activated AR supports the negative feedback regulation of glucocorticoid production via up-regulation of GR expression in the pituitary gland.     

Cellular localization of androgen and estrogen receptors in mouse-derived motoneuron hybrid cells and mouse facial motoneurons

The ability of gonadal steroid hormones to augment axonal regeneration after peripheral nerve injury has been well established in rat and hamster motoneuron systems, and provides a foundation for the use of these agents as neurotherapeutics. With the advent of mouse genetics and the availability of transgenic and knockout mice, the use of mice in studies of neuroprotection is growing. It has recently been demonstrated that both androgens and estrogens rescue motoneurons (MN) from injury in mouse-derived motoneuron hybrid cells in vitro and mouse facial motoneurons (FMN) in vivo (Tetzlaff et al. [2006] J Mol Neurosci 28:53-64). To elucidate the molecular mechanisms of these effects, the present study examined the cellular localization of androgen and estrogen receptors in mouse MN in vitro and in vivo. Immunoblotting and immunocytochemistry studies established the presence of androgen receptor (AR) and estrogen receptor alpha/beta in immortalized mouse motoneuron hybrid cells and AR and estrogen receptor alpha in mouse FMN.     

The effect of dihydrotestosterone on the estrogen-induced cytodifferentiation of the chick oviduct

The androgenic effects on the estrogen-induced cytodifferentiation of the chick oviduct epithelium were investigated. Dihydrotestosterone was shown to have an effect on the organization of stromal cells. Since these cells contained androgen receptor (AR), it is reasonable to assume an involvement of androgens in the differention and functioning of these cells through a direct action. Immunohistochemical analysis revealed a wide distribution of AR. AR was shown to be expressed in both the endothelial and smooth musle cells of blood vessels. In the immature oviduct AR was located in the epithelial, mesenchymal and mesothelial cells. In the differentiating oviduct, whether induced by exogenous estrogen or normally by endogenous hormones, AR was also expressed by the tubular gland cells. Dihydrotestosterone alone had no effect on the morphology of the immature oviduct, suggesting the involvement of the determinants of differentiation in the action of androgen together with estrogen.     

Cell-specific distributions of estrogen receptor alpha (ERα) and androgen receptor (AR) in anterior pituitary glands from adult cockerels as revealed by immunohistochemistry

Estrogens and androgens play important roles in regulating the hormone-secreting functions of the pituitary gland by binding to their corresponding receptors. However, the expression of estrogen receptors (ERs) and the androgen receptor (AR) and the cell types containing ERs and AR in the anterior pituitary gland of adult chickens have not been well-studied. In this study, the distribution of ERα, AR and their corresponding cell types in the anterior pituitary gland of adult cockerels was detected by immunohistochemistry. The results showed that ERα was expressed in 68.63 % of luteinizing hormone (LH) producing cells but was not found in thyrotropes, lactotropes, somatotropes, corticotropes and folliculo-stellate (FS) cells. Pituitary hormone and AR double labeling results showed that about 37 % of LH cells and 50 % of thyroid-stimulating hormone (TSH) producing cells expressed AR, respectively. In contrast, less than 1 % of the somatotropes had an AR positive signal and AR signals were not detected in lactotropes, corticotropes or FS cells. In addition, there were only a few AR and ERα dual-labeled cells observed. These novel results provide evidence for a cell-specific distribution of ERα and AR in the anterior pituitary from adult cockerels by immunohistochemistry. The different distributions of ERα and AR in the LH cells suggest that the feedback-regulating mechanisms of estrogen and androgen on the pituitary hormones secretion are different. The functions and related mechanisms still need to be elucidated further.     

Testosterone and estradiol up-regulate androgen and estrogen receptors in immature and adult rat thyroid glands in vivo

Thyroid gland is one of the non-classical target organs for sex steroids. Presence of androgen and estrogen receptors in the neoplastic and non-neoplastic thyroid glands of mammalian species is well documented. The aim of the present study is to elucidate the changes in serum and thyroidal sex steroids, and their receptors in the thyroid gland of rats from immature to adult age under gonadectomized (GDX) and sex steroids replaced conditions. Normal Wistar male and female rats from immature to adult age (day 21, 30, 45, 60 and 160 post-partum (pp)) were used in the present study. One group (I) of rats was GDX at an early age (day 10 pp) and the other group (II) at the adult age (day 120 pp). Group I rats were sacrificed at different experimental periods such as 21, 30, 45 and 60 days pp, and group II rats were sacrificed at day 160 pp. Another group of GDX rats from group I and II were replaced with physiological doses of testosterone or estradiol. Serum and thyroidal concentrations of sex steroids were estimated by RIA method and the concentrations of receptors by radioreceptor assay. Gonadectomy significantly decreased serum and thyroidal testosterone and estradiol and concentrations of androgen receptor (AR) and estrogen receptor (ER) in the thyroid. Replacement of sex steroids to GDX rats restored the normal level of sex steroids, AR and ER. Therefore, it is suggested from the present study that (i). sex steroids up-regulate their own receptors in the thyroid, (ii). sex steroids may influence thyroid growth and the proliferation of thyrocytes by modulating their receptor concentrations in the thyroid.     

Androgen receptor in rat Harderian and submandibular glands

Summary Androgens regulate the development and sexual dimorphism of rodent Harderian and submandibular glands. This effect is believed to be mediated by the androgen receptor. Immunohistochemistry and immunoblotting were carried out to study the receptor in normal, castrated and dihydrotestosterone-supplemented rat Harderian and submandibular glands. Immunohistochemically, the most intense nuclear staining was observed in the acinar cells of the submandibular glands, followed by intercalated duct cells. The granular convoluted tubules showed weak immunostaining and the striated ducts were negative. In the Harderian gland, nuclear staining was seen in both type I and II secretory cells. Castration and treatment had no effect on the expression of the androgen receptor protein in either gland. A 110 K androgen receptor signal was detected by immunoblotting in the Harderian gland but not in the submandibular gland. An experiment was designed to explore the possible effect of proteinases on the receptor protein in the homogenate of submandibular gland. Our results demonstrate the cell-specific location of the receptor in Harderian and submandibular glands, and show that the expression of the receptor protein is androgen-independent.     

Sex steroid and thyroid hormone receptor expressions in the thyroid of the American alligator (Alligator mississippiensis) during different life stages

The expression of estrogen receptors, ESR1 (ERα) and ESR2 (ERβ), and androgen receptors (AR) in the thyroid gland has been reported in few vertebrate species other than a few mammals. This study reports the presence of sex steroid hormone receptors and thyroid receptors (ERα, ERβ, AR, TRα, and TRβ) in the thyroid gland of the American alligator at several life stages. It provides a semiquantification and distribution of ERα in the thyroid follicle cells using an immunohistochemical approach as well as reports quantitative differences in mRNA expression of ERα, ERβ, TRα, TRβ, and AR in the same tissue using quantitative real time‐PCR (Q‐PCR) with primers designed specifically for alligators. The thyroid tissue of the American alligator expresses ERα, ERβ, and AR at all of the life stages examined here although no statistically significant differences were observed between male and female in thyroid mRNA expression for any of the genes analyzed. No sexual dimorphism was observed in ERα immunostaining. No statistical analysis across life stages were performed due to confounding factor of season. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

视黄醇结合蛋白RBP4可与多种核受体相互作用

视黄醇结合蛋白 (retinolbindingprotein ,RBP4 )是体内一种重要的转运蛋白 ,主要负责结合、转运全反式视黄醇 (维生素A ,VitA ) .VitA及其衍生物如11 cis 视黄醛、all trans 视黄酸等 ,均是体内非常重要的疏水分子 ,与视觉循环、胚胎发育等多种过程有关 .RBP4的功能障碍会导致     

Topographic recognition of cyclic hydrocarbons and related compounds by receptors for androgens, estrogens, and glucocorticoids

The structural requirements for the interaction of about 80 cyclic hydrocarbons and related compounds with the androgen receptor of rat ventral prostate, the estrogen receptor of human breast tumor MCF-7 cells, and the glucocorticoid receptor of rat liver were examined by comparing their abilities to compete with radioactive hormones for binding to the respective receptors. The results indicate that the receptor-binding affinity of a compound is dependent on its electronic configuration and geometrical similarity to a portion of a natural steroid hormone which can be recognized by local ligand-binding sites in the receptor. For the estrogen receptor, beta-phenols are more active than the corresponding alpha-phenols, whereas nonphenolic compounds are totally inactive. For androgen and glucocorticoid receptors, alpha-phenols are more active than beta-phenols. The androgen receptor can interact stereospecifically with nonoxygenated and nonalkylated cyclic hydrocarbons, such as 10,11-dihydro-5H-dibenzo[a,d] cycloheptene or 9,10-dihydrophenanthrene, which can, in vivo, inhibit the androgen-dependent growth of the male accessory reproductive organs. The affinities of naphthalene, anthracene, phenanthrene, biphenyl, and adamantane toward glucocorticoid and androgen receptors can be enhanced by acetylation or ethanolization of these ligands. Our results also indicate that, while the hormonal action of a steroid may be dependent on the interaction of a functional group on the hormone with a specific group on the receptor, the presence of such a group may not be required for the antagonistic activity of a compound that can physically block hormone binding to the receptor. Thus, many small molecules that were hitherto considered to be biologically inert may interact with steroid receptors specifically and affect hormonal activities in vivo.     

Negative regulation of parathyroid hormone-related protein expression by steroid hormones

Elevated parathyroid hormone-related protein (PTHrP) is responsible for humoral hypercalcemia of malignancy (HHM), which is of clinical significance in treatment of terminal patients with malignancies. Steroid hormones were known to cause suppression of PTHrP expression. However, detailed studies linking multiple steroid hormones to PTHrP expression are lacking. Here we studied PTHrP expression in response to steroid hormones in four cell lines with excessive PTHrP production. Our study established that steroid hormones negatively regulate PTHrP expression. Vitamin D receptor, estrogen receptor α, glucocorticoid receptor, and progesterone receptor, were required for repression of PTHrP expression by the cognate ligands. A notable exception was the androgen receptor, which was dispensable for suppression of PTHrP expression in androgen-treated cells. We propose a pathway(s) involving nuclear receptors to suppress PTHrP expression.     

MCF-7; a human breast cancer cell line with estrogen, androgen, progesterone, and glucocorticoid receptors.

We have identified receptors for glucocorticoids, progestins, and androgens in a human breast tumor cell line (MCF-7) known to have estrogen receptor. Sucrose density gradients show that MCF-7 cytosol contains approximately 100 fm/mg protein estradiol (E2-3H) receptor, more than 300 fm/mg protein progesterone receptor (measured with R5020-3H), about 40 fm/mg protein 5alpha-dihydrotestosterone (5alpha-DHT-3H) receptor, and 800 fm/mg glucocorticoid receptor (measured with dexamethasone-3H). Dissociation constants obtained by Scatchard analyses were approximately 0.6 x 10(-10)M (E2), 1 x 10(-9)M (R5020), 2.8 x 10(-10)M (5alpha-DHT) and 8 x 10(-9)M (dexamethasone). No cross competition was found for estrogen receptor, but progestins competed for androgen and glucocorticoid binding. The androgen, but not the glucocorticoid, partially competed for R5020 binding to progesterone receptor. This first demonstration of 4 classes of steroid receptors in human breast cancer means that MCF-7 may be an excellent in vitro model for studying the mechanism of tumor response to endocrine therapy as well as the complex relationships between binding and biological actions of these hormones.     

The androgen receptor mRNA is up-regulated by testosterone in both the harderian gland and thumb pad of the frog, Rana esculenta

³²P-labelled cDNA probe from plasmid containing rat androgen receptor (rAR) has been tested in hybridization experiments using RNAs from the Harderian gland and thumb pad of the edible frog, Rana esculenta. Northern blot analysis has shown a high degree of homology between the rAR cDNA and the frog androgen receptor mRNA (fAR mRNA); this has been supported by both the hybridization conditions (high stringency) and the molecular size of fAR mRNA which is quite similar to those described in mammals (9.4 kb). The role of androgens has been further investigated with respect to the kinetics of expression of fAR mRNA in in vivo experiments. In both the Harderian gland and thumb pad, testosterone has increased the levels of fAR mRNA as compared with the untreated groups. The use of cyproterone acetate (CPA) in combination with testosterone has resulted in a loss of the increase in fAR mRNA as compared to testosterone-treated groups, while CPA alone has resembled the control group. In primary cultures of frog Harderian gland and thumb pad cells, the steady-state levels of fAR mRNA have been increased in the cells exposed to testosterone as compared to those not exposed. These findings confirm that, in these androgen target tissues, testosterone exerts an up-regulation on its own receptors, increasing the accumulation of fAR mRNA in the same way as oestrogens up-regulate the expression of their own receptors in Xenopus liver and oviduct cells.     

Hormonal effects on hamster lacrimal gland female-specific major 20 kDa secretory protein and its immunological similarity with submandibular gland major male-specific proteins

Hormonal regulation of a major 20 kDa protein of hamster exorbital lacrimal gland (LG) was studied by SDS-PAGE profile analysis and the purified protein's antisera was used to screen tissues of hamster and other species for crossreacting proteins. This protein was seen in female LG but not in males and late-pregnant or hCG-treated females. Low estrogen state in females after gonadectomy, prolonged light-deprivation, prolonged starvation or lactation increased its level several folds to 20% of LG soluble proteins and similar levels were induced in males after gonadectomy (low androgen state). However, light-deprivation or melatonin treatment-induced low androgen state in males had no effect. In gonadectomized hamsters, this LG protein was obliterated on treatment with androgens, estrogens or thyroid hormones. Only estrogen inhibition of LG 20 kDa was prevented by simultaneous tamoxifen administration. Simultaneous treatment of gonadectomized hamsters with gonadotrophins and estrogen/androgen did not prevent the LG 20 kDa protein's inhibition. Relative potencies of estrogens (3.6 μg daily dose) were: estradiol-17βdiethylstilbestrol>estrone>estradiol-17, while estriol and chlorotrianisene had no effect. Dexamethasone, progesterone, prolactin, hypothyroid state or adrenalectomy had no effect on LG 20 kDa expression. Western blot studies confirmed the marked repression of LG 20 kDa by estrogen androgen and thyroid hormone and detected the protein in tears of females and gonadectomized hamsters but not in males. Interestingly, among other tissues tested, crossreaction was only seen with the estrogen-repressed 24 and 20.5 kDa major male-specific secretory proteins of hamster submandibular glands (SMG) which were previously reported by us. This strongly indicated that the LG and SMG proteins are products of the same or closely related genes. A possible role for these hamster sex-specific LG and SMG major secretory proteins in olfactory communication is suggested.     

Immunohistochemical detection of androgen receptors in the canine uterus throughout the estrus cycle

Serum androgen levels in the bitch increase during proestrus and remain elevated until metestrus. To find out whether androgens can have a direct impact on the canine uterus, androgen receptors (AR) were identified immunohistochemically in uterine tissue. Androgen receptor distribution in the uterine horns, body and cervix was described during different cycle stages, during pregnancy and in the postpartum period. Nuclear staining for AR was observed in cells of the surface epithelium, glandular ducts, basal glands and stroma of the endometrium, and in myometrial smooth muscle cells. In addition, cytoplasmic staining was observed in epithelial cells from proestrus to early metestrus, when the cells were secretory active, and in stroma cells during pregnancy, suggesting a role for androgens in decidualization. During pregnancy and in the postpartum period nuclear staining for AR was nearly absent. During the estrus cycle stroma cells stained with higher intensities for AR than epithelial cells, supporting the idea that stroma cells mediate some effects of steroid hormones on epithelial cells in the genital tract. In contrast with earlier findings on estrogen receptor-alpha and progesterone receptors, no significant changes in androgen receptor expression were observed during the estrus cycle. Few correlations were found between the staining for AR and serum levels of the sex steroids. The present findings suggest that there is a basal expression of AR in the canine uterus throughout the estrus cycle that may not be influenced by sex steroid hormones.