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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Absorption, fluorescence and excitation fluorescence spectra of pheophytin a have been measured in aqueous solutions of nonionic (Triton X-100), anionic (sodium lauryl sulphate) and cationic (Cetyl pyridinium chloride) detergents at different concentrations and pH after system relaxation. By measuring the second derivative and differential spectra, it has been shown, that if detergent concentrations are lower than critical micelles concentration, or if the detergent is completely absent, the pigment forms conglomerates containing both dimeric and monomeric forms with an efficient energy transfer between them. If detergent concentrations are higher than critical micelles concentration, pheophytin a localizes in detergent micelle in monomeric form at neutral and acidic pH, and allomerizes at alkaline pH. The spectral characteristics of pheophytin a dimers in the conglomerate and its monomers in micelles poorly (if at all) depend on the sign of the detergent molecule charge.
Mol Biol (Mosk)
PMID:[Molecular organization of pheophytin a in aqueous solutions of detergents]. 650 34

The androgen receptor (AR) was localized immunohistochemically after different hormonal treatments in the ventral prostate, coagulating gland, seminal vesicle and epididymis of the adult rat. In the untreated controls AR-immunoreactivity was confined to the cell nuclei. One week after castration or treatment with the gonadotropin-releasing hormone antagonist Cetrorelix (150 micrograms/animal per day) a cytoplasmic staining occurred in the epithelial cells of the ventral prostate and in part of the coagulating gland and seminal vesicle. In contrast, the AR remained exclusively in the nuclei in the epididymal epithelium and the glandular smooth muscle layer even after 2 weeks of androgen depletion. Bolus injections of either dihydrotestosterone (1 mg/kg), the antiandrogen flutamide (40 mg/kg), or the novel non-steroidal antiandrogen casodex (40 mg/kg) to androgen-depleted animals eliminated cytoplasmic AR-immunoreactivity and restored the nuclear staining pattern in the ventral prostate. A sustained 2-week treatment with the antiandrogens resulted in a loss of weight in all organs but did not alter the distribution of AR-immunoreactivity. The data show an apparent cytoplasmic/nuclear ligand-dependent translocation of the AR in the ventral prostate, coagulating gland and seminal vesicle but not in the epididymis of the adult rat.
J Steroid Biochem Mol Biol 1994 Jan
PMID:The effect of androgens and antiandrogens on the immunohistochemical localization of the androgen receptor in accessory reproductive organs of male rats. 813 98

In the male rat, testosterone has been shown to regulate gonadotrophin synthesis and secretion under experimental conditions such as castration or gonadotrophin-releasing hormone (GnRH) antagonist with or without testosterone. The present study aims at clarifying the effects of non-steroidal antiandrogens, Casodex and flutamide, and ethane dimethane sulphonate (EDS) on the regulation of gonadotropin synthesis and secretion. To enable a direct comparison within this study to expected effects of testosterone, a GnRH antagonist-treated group and a castrated group were included. The gene expression of the subunits was correlated with changes in the pituitary and plasma content of immunoreactive luteinizing hormone (LH) and follicle-stimulating hormone (FSH), free subunits and pituitary content of in vitro bioactive LH and FSH. Groups of ten male rats each received the following treatments for 7 days: (1) vehicle; (2) castration; (3) EDS (75 mg/kg); (4) GnRH antagonist (Cetrorelix 250 micrograms/kg/day), (5) Casodex (20 mg/kg/day) or (6) flutamide (20 mg/kg/day). The effectiveness of testosterone deprivation was demonstrated by the reduction of weight in androgen-dependent organs such as epididymides and seminal vesicles in the treated groups. Treatment with flutamide, EDS or castration significantly increased (p < 0.05) serum levels of LH, FSH and alpha-subunit, whereas serum gonadotrophin levels were decreased in the GnRH antagonist-treated group. alpha-Subunit mRNA levels were elevated in the castrated, EDS and flutamide group and LH-beta mRNA levels were increased in the castrated and EDS group. FSH-beta mRNA levels were increased in the castrated group and decreased in the GnRH antagonist group, but remained unchanged in the flutamide and EDS group.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1993 Feb
PMID:Effects of antiandrogens and ethane dimethane sulphonate (EDS) on gene expression, free subunits, bioactivity and secretion of pituitary gonadotrophins in male rats. 838 9

1. Two eukaryotic viral systems, the baculovirus/insect cell and the Semliki Forest virus systems, were tested for heterologous expression of human gonadotropin-releasing hormone receptor (GnRHR) cDNA. 2. An unmodified as well as a c-myc epitope-tagged human GnRH receptor was produced in two insect cell lines (Spodoptera frugiperda, Trichoplusia ni) after infection with the respective recombinant baculoviruses. In both insect cell lines, the receptor was identified by immunoblot analysis as a triplet of bands between 35 and 40 kDa. After deglycosylation of the receptor the molecular mass decreased to 35 kDa. The GnRH receptor was localized in membrane compartments within the infected insect cells. However, only in membranes of infected Trichoplusia ni insect cells could approximately 2000 receptors per cell be detected. 3. Production of the GnRH receptor in BHK cells using the Semliki Forest virus system resulted in approximately 50,000 receptors per cell. A maximal yield of 0.42 pmol/mg membrane protein was obtained 24 hr after electroporation of BHK cells with in vitro synthesized RNA. Binding of the antagonist [125I]Cetrorelix was saturable with a KD of 1.3 nM. The receptor produced in the BHK cells was further characterized by ligand displacement studies. The rank order of agonist and antagonist affinities was Cetrorelix > Triptorelin > Antide > GnRH.
Cell Mol Neurobiol 1998 Oct
PMID:Characterization of the human gonadotropin-releasing hormone receptor heterologously produced using the baculovirus/insect cell and the Semliki Forest virus systems. 977 51

To investigate the role of leptin during pregnancy, we assessed leptin production by pure cultured human cytotrophoblastic cells (CTB), its regulation by cytokines and 17beta-oestradiol and its effects on human chorionic gonadotrophin (HCG) secretion. Purified CTB from first trimester placenta were incubated in duplicates in the presence or absence of cytokines or 17beta-oestradiol. Medium was harvested on day 2 and the culture stopped on day 4. Results were corrected for protein content of each individual well and expressed as percent of controls per day (mean +/- SEM). Basal CTB leptin production was 25.2 +/- 2.6 (ng/mg prot). In comparison with controls, leptin production was stimulated to 320 +/- 16% (P < 0.0001) and 195 +/- 3.2% (P < 0.0004) by 3 and 10 ng/ml of interleukin-1alpha respectively. 17beta-oestradiol 10(-6) to 10(-9) mol/l increased basal leptin production 5-9-fold, while 10(-5) mol/l had no such effect. Basal CTB HCG secretion was 5722 +/- 1055 (mIU/mg prot). There was a dose-dependent leptin-induced increase in HCG secretion (P = 0.0039) reaching a 5-fold increase with a leptin concentration of 1 microg/ml (P < 0.006). Gonadotrophin-releasing hormone (GnRH) 8.5 x 10(-8) mol/l significantly increased HCG secretion to 140 +/- 21% of controls (P = 0.031). Cetrorelix (0.1 microg/ml) inhibited leptin-induced HCG secretion (P = 0.0028).
Mol Hum Reprod 1999 Nov
PMID:Modulation of human cytotrophoblastic leptin secretion by interleukin-1alpha and 17beta-oestradiol and its effect on HCG secretion. 1054 71

To understand the ligand binding properties of the human GnRH receptor (hGnRH-R), 24 site-specific mutants within transmembrane helices (TMH) 1, 2, and 5 and the extracellular loop 2 (E2) were generated. These mutants were analyzed by using a functional reporter gene assay, monitoring receptor signaling via adenylate cyclase to a cAMP-responsive element fused to Photinus pyralis luciferase. The functional behavior of 14 receptor mutants, capable of G-protein coupling and signaling, was studied in detail with different well described agonistic and antagonistic peptide ligands. Furthermore, the binding constants were determined in displacement binding experiments with the antagonist [125I]Cetrorelix. The substitution of residues K36, Q204, W205, H207, Q208, F20, F213, F216, and S217 for alanine had no or only a marginal effect on ligand binding and signaling. In contrast, substitution of N87, Eg9, D9, R179, W206, Y211, F214, and T215 for alanine resulted in receptor proteins neither capable of ligand binding nor signal transduction. Within those mutants affecting ligand binding and signaling to various degrees, W101A, N102A, and N212Q differentiate between agonists and antagonists. Thus, in addition to N102 already described, the residues W101 in TMH2 and N212 in TMH5 are important for the architecture of the ligand-binding pocket. Based on the experimental data, three-dimensional models for binding of the superagonist D-Trp6-GnRH (Triptorelin) and the antagonist Cetrorelix to the hGnRH-R are proposed. Both decapeptidic ligands are bound to the receptor in a bent conformation with distinct interactions within the binding pocket formed by all TMHs, E2, and E3. The antagonist Cetrorelix with bulky hydrophobic N-terminal amino acids interacts with quite different receptor residues, a hint at the failure to induce an active, G protein-coupling receptor conformation.
Mol Endocrinol 2000 Jul
PMID:Residues within transmembrane helices 2 and 5 of the human gonadotropin-releasing hormone receptor contribute to agonist and antagonist binding. 1089 58

Gonadotropin-releasing hormone (GnRH) regulates the reproductive system through the cognate GnRH receptor (GnRHR) in vertebrates. In this study, we cloned a cDNA encoding the full-length open reading frame sequence for green monkey type-II GnRHR (gmGnRHR-2) from the genomic DNA of CV-1 cells. Transient transfection study showed that gmGnRHR-2 was able to induce both c-fos promoter- and cAMP responsive element-driven transcriptional activities, indicating that gmGnRHR-2 couples to both Gs- and Gq/11-linked signaling pathways. gmGnRHR-2 responded better to GnRH-2 ([His5, Trp7, Tyr8]GnRH) than GnRH-1 ([Tyr5, Leu7, Arg8]GnRH). Substitutions of His5, Trp7, and/or Tyr8 in GnRH-1 increased the potency to activate gmGnRHR-2, suggesting that individual His5, Trp7, and Tyr8 in GnRH-2 contributed to differential ligand sensitivity of gmGnRHR-2. Substitution of D-Ala for Gly6 in GnRH-2 increased the potency to activate the receptor, suggesting that GnRH-2 has a constrained conformation when it binds to the receptor. GnRH-induced gmGnRHR-2 activation was specifically inhibited by GnRH-2 antagonists, Trptorelix-1 and -2, but not by a GnRH-1 antagonist, Cetrorelix. In conclusion, gmGnRHR-2 revealed preferential ligand selectivity for GnRH-2 and its analogs, suggesting that gmGnRHR-2 has a functional activity that is different from mammalian type-I GnRHRs but similar to non-mammalian GnRHRs.
Mol Cell Endocrinol 2003 Nov 14
PMID:Preferential ligand selectivity of the monkey type-II gonadotropin-releasing hormone (GnRH) receptor for GnRH-2 and its analogs. 1460 14

Recently, we identified three types of non-mammalian gonadotropin-releasing hormone receptors (GnRHR) in the bullfrog (designated bfGnRHR-1-3), and a mammalian type-II GnRHR in green monkey cell lines (denoted gmGnRHR-2). All these receptors responded better to GnRH-II than GnRH-I, while mammalian type-I GnRHR showed greater sensitivity to GnRH-I than GnRH-II. In the present study, we designed new GnRH-II analogs and examined whether they activated or inhibited non-mammalian and mammalian type-II GnRHRs. [D-Ala6]GnRH-II, with D-Ala substituted for Gly6 in GnRH-II, increased inositol phosphate (IP) production in cells stably expressing non-mammalian GnRHRs more effectively than native GnRH-II. However, it exhibited lower activity for mammalian type-I GnRHR than GnRH-I itself. Trptorelix-1, a GnRH-II antagonist, inhibited GnRH-induced IP production in cells expressing non-mammalian GnRHRs more effectively than Cetrorelix, a GnRH-I antagonist. Trptorelix-1, however, had lower potency for mammalian type-I GnRHR than Cetrorelix. Ligand-receptor binding assays revealed that [D-Ala6]GnRH-II and Trptorelix-1 have higher affinities for non-mammalian GnRHRs but lower affinities for mammalian type-I GnRHR than GnRH-II and Cetrorelix, respectively. Moreover, [D-Ala6]GnRH-II and Trptorelix-1 had a higher affinity for gmGnRHR-2 than GnRH-II and Cetrorelix, respectively. These results indicate that [D-Ala6]GnRH-II and Trptorelix-1 are highly effective agonist and antagonist, respectively, for non-mammalian and type-II mammalian GnRHRs.
Mol Cells 2003 Oct 31
PMID:GnRH-II analogs for selective activation and inhibition of non-mammalian and type-II mammalian GnRH receptors. 1465 Dec 58

We have examined the role of 17beta-estradiol and gonadotropin releasing hormone (GnRH) in the regulation of functional differentiation in human trophoblasts. In contrast to its recognized functions as a proliferation-promoting hormone in a variety of cell types, we found that 17beta-estradiol induced terminal differentiation in human trophoblastic cells, and that this event was estrogen-receptor-mediated. This process involved a loss in expression of Cyclins A2 and E, and a coincident increase in p27(Kip1). The anti-proliferative effects of 17beta-estradiol were annulled by specific transforming growth factor-beta 1 (TGFbeta1)-neutralizing antibody, suggesting that 17beta-estradiol may mediate its growth-inhibitory actions, through TGFbeta1 activity. Following exposure to Buserelin, cultured human trophoblastic cells stopped proliferating and formed functionally mature syncytiotrophoblasts. This differentiation event, that involved a drastic loss in expression of proliferating-cell-nuclear-antigen, could be blocked by Cetrorelix, suggesting the involvement of functional GnRH receptors. Preliminary studies on the characterization of the human placental GnRH receptor, indicate the presence of multiple receptor isoforms across human gestation.
Mol Cell Endocrinol 2004 Apr 15
PMID:Hormonal regulation of human trophoblast differentiation: a possible role for 17beta-estradiol and GnRH. 1513 May 13

Recently, GnRH antagonists (GnRHant) like cetrorelix and ganirelix have been introduced in protocols of controlled ovarian hyperstimulation for assisted reproductive techniques to prevent premature luteinizing hormone (LH) surges. Here we tested, whether the actions of cetrorelix and the GnRH agonist (GnRHag) triptorelin in gonadotrophs are dependent on the steroid milieu. Furthermore, we characterized the actions of cetrorelix and triptorelin on LH secretion and the total LH pool. Female rat pituitary cells were treated either with 0.1 nM triptorelin for 1, 2, 4 and 6 days or for 1, 3, 5 and 6 h or with 1, 10 or 100 nM cetrorelix for 1, 2, 3 and 5 h or for 10 min. Cells were stimulated for 3h with different concentrations of GnRH (10 pM-1 microM). For analysis of the total LH pool, which is composed of stored and released LH, cells were lysed with 0.1% Triton X-100 at -80 degrees C overnight. To test, whether the steroid milieu affects the actions of cetrorelix and triptorelin, cells were incubated for 52 h with 1 nM estradiol (E) alone or with combinations of 100 nM progesterone (P) for 4 or 52 h, respectively. Cells were then treated with 0.1 nM triptorelin for 9 h or 1 nM cetrorelix for 3 h and stimulated for 3 h with different concentrations of GnRH (10 pM-1 microM). The suppressive effect of triptorelin on LH secretion was fully accomplished after 3 h of treatment, for cetrorelix only 10 min were sufficient. The concentration of cetrorelix must be at least equimolar to GnRH to block LH secretion. Cetrorelix shifted the EC50s of the GnRH dose-response curve to the right. Triptorelin suppressed total LH significantly (from 137 to 36 ng/ml) after 1 h in a time-dependent manner. In contrast, only high concentrations of cetrorelix increased total LH. In steroid treated cells the suppressive effects of triptorelin were more distinct. One nanomolar cetrorelix suppressed GnRH-stimulated LH secretion of cells not treated with steroids from 10.1 to 3.5 ng/ml. In cells, additionally treated with estradiol alone or estradiol and short-term progesterone, LH levels were higher (from 3.5 to 5.4 or 4.5 ng/ml, respectively). In cells co-treated with estradiol and progesterone for 52 h LH secretion was only suppressed from 10.1 to 9.5 ng/ml. Steroid treatments diminished the suppressive effect of cetrorelix on LH secretion. In conclusion, the depletion of the total LH pool contributes to the desensitizing effect of triptorelin. The actions of cetrorelix and triptorelin are dependent on the steroid milieu.
J Steroid Biochem Mol Biol 2006 Oct
PMID:Actions of gonadotropin-releasing hormone analogues in pituitary gonadotrophs and their modulation by ovarian steroids. 1689 Nov 15


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