Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A membrane preparation was obtained from rat striated muscle. The preparation used has been shown to contain plasma membranes by electron microscopy as well as by enrichment in specific activity of both a plasma membrane enzyme "marker" (5'-nucleotidase) and cell surface 125I-incorporated radioactivity. The characteristics of 125I-insulin binding to this striated muscle preparation were studied, and it was found that 125I-insulin readily and specifically binds to this membrane preparation. The binding reaction was time, pH, and temperature dependent with optimal steady-state binding conditions occurring at 20 degrees C and at pH 7.6. Under these conditions (20 degrees C, pH 7.6) skeletal muscle plasma membranes displayed little ability to degrade insulin. Binding of 125I-insulin was readily inhibited at physiologic concentrations of unlabeled insulin and the specificity of this receptor for insulin was demonstrated by finding that high concentrations of glucagon, b-LH, b-FSH, p-PRL, hCG, TSH, and HGH were without effect on 125I-insulin binding and that insulin analogues inhibited binding in proportion to their biologic activity. When membranes from older, fatter rats were compared to membranes from younger, lean animals, 5'-nucleotidase specific activity and insulin degrading activity were found to be comparable. On the other hand, insulin binding to membrane receptors was decreased 30%-40% in the older, fatter animals. Thus, these studies indicate that (1) specific insulin receptors exist in skeletal muscle plasma membranes, and (2) membranes from older, fatter rats have fewer receptors than those from younger, lean animals.
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PMID:Insulin receptors of skeletal muscle: specific insulin binding sites and demonstration of decreased numbers of sites in obese rats. 0 34

Effects of various hormonal and pharmacological manipulations on somatostatin distribution were investigated to elucidate the physiological significance of somatostatin in the hypothalamus and the other regions of the rat brain. Immunoreactive somatostatin (IRS) was measured by radioimmunoassay newly developed. Insulin induced an increase of hypothalamic IRS and a decrease of plasma RGH, while glucose administration resulted in the opposite responses, which were not significant. Insulin also increased IRS in the thalamus and the brain stem. The insulin-induced increase of hypothalamic IRS was reduced by hyperglycemia. Glucagon reduced IRS initially and then increased it with an elevation plasma RGH. L-dopa did not affect hypothalamic IRS, although it decreased plasma RPRL. Phentolamine slightly increased plasma RGH and decreased IRS in most regions of the rat brain, while propranolol increased IRS in these regions. Pretreatment with propranolol significantly increased plasma RGH 120 min after insulin administration, and hypothalamic IRS decreased initially by pretreatment with propranolol, and then it increased significantly. When pretreated with propranolol, glucagon markedly increased plasma RGH and decreased IRS significantly. From these findings it is concluded that hypothalamic IRS may participate in the hormonal regulatory system in correlation to plasma RGH, as observed in studies on plasma GH and hypothalamic IRS following insulin, glucose, propranolol or phentolamine administration, but IRS in other regions of the brain may have some other actions as a neurotransmitter or a modulator, because of no significant correlation between plasma GH or PRL and IRS in these regions following various stimuli. In addition, glucose homeostasis and adrenergic mechanism may be important factors in regulating IRS in the rat brain.
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PMID:Immunoreactive somatostatin in the hypothalamus and other regions of the rat brain: effects of insulin, glucose, alpha- or beta-blocker and L-dopa. 3 44

The specific binding of 125I-labeled insulin, human hormone ([125I]hGH), bovine growth hormone ([125I]bGH), and ovine prolactin ([125I]oPRL) was studied in mouse liver membranes. [125I]hGH and [125I]oPRL bound to adult liver membranes. Pregnancy increased the specific binding of [125I]hGH but not that of [125I]oPRL. [125I]hGH was displaced from membranes of pregnant mice by hGH, oPRL, and bGH, but only by hGH and oPRL from liver membranes of nonpregnant mice. Significant specific binding of [125I]bGH was seen only in pregnancy. The binding of [125I]bGH to pregnant mouse liver membranes increased with increasing concentration of either membrane protein or [125I]bGH. Both the specific binding and dissociation of [125I]bGH were greatly influenced by the time and temperature of incubation. Binding of [125I]bGH was inhibited by growth hormones, including hGH and rat GH, and not by lactogenic hormones (various prolactins and human placental lactogen), ACTH, glucagon, or insulin. The inhibition of [125I]hGH binding by hGH and bGH, in the presence of excess (2 mug/ml) of PRL, was very similar to that seen with [125I]bGH. Scatchard plots of displacement dose-response curves obtained under steady state conditions of 4C were nonlinear and very similar with either [125I]bGH or [125I]hGH. This contrasted with the linear Scatchard plots obtained from displacement dose-response curves of either [125I]oPRL or [125I]hGH in the presence of excess (2 mug/ml) bGH. Termination of pregnancy, either naturally or by hysterectomy, reduced [125I]bGH specific binding to nonpregnant levels by 24 to 36 h. Estrogen administration did not increase [125I]bGH binding in hepatic membranes. Nonpregnant mice possess hepatic lactogen binding sites which are uninfluenced by pregnancy. GH specific binding sites are markedly augmented during pregnancy. The close correlation between the level of these sites and pregnancy suggests that they are regulated by a product of the fetoplacental unit.
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PMID:Characterization and modulation of growth hormone and prolactin binding in mouse liver. 17 65

Previously, we have shown that preparations of hCG bind to bovine thyroid membranes, as judged from their ability both to inhibit the binding of 125I-labeled bovine TSH (bTSH) and to activate adenylate cyclase (Amir, S.M., H. Uchimura, and S.H. Ingbar, J Clin Endocrinol Metab 45: 280, 1977). In the present studies, 125I-labeled, highly purified bTSH ([125I]bTSH) has been shown to bind specifically and saturably to receptors in a particulate fraction from rat testis. At 37 C, binding was rapid, reaching a maximum level in less than 15 min, but then declining markedly during the next several hours. At 22 C, binding reached a steady state after 2 h and remained unchanged for another 22 h. Binding of [125I]bTSH was greatest at pH 5.5, at which pH more than 50% of [125I]bTSH was bound in the presence of 330 microgram/ml particulate protein, the concentration of protein that yielded maximum binding. Nevertheless, the majority of experiments were conducted at lesser protein concentrations and at physiological pH (7.45), under which conditions total binding was only 25% of that measured at pH 5.5. Scatchard plots indicated the presence of a single binding site with a dissociation constant of 5.8 X 10(-8) M and a binding capacity of 0.22 nmol/mg protein on the basis of data obtained at 22 C and pH 7.45. Both crude and highly purified preparations of hCG inhibited the binding of [125I]bTSH to testis particulate fraction; crude hCG had 46 times the activity, and purified hCG had only one-tenth the activity of bTSH itself in this respect. This was true despite the fact that with respect to the displacement of [125I]hCG, crude and purified hCG were almost equally active. Bovine LH had one-third the activity of bTSH in displacing [125I]bTSH. Human FSH inhibited [125I]bTSH binding only slightly at the highest concentration tested, while glucagon, insulin, PRL, and GH were inactive. Purified bTSH inhibited the binding of [125I]hCG to testis particulate fraction but contained only about 2% of the activity of purified hCG. Lineweaver-Burk analysis suggested that inhibition of [125I]hCG binding by bTSH was competitive in nature. Purified bTSH stimulated cAMP production in Leydig cells, but with only about 0.1% of the activity of purified hCG. It is concluded that bTSH binds reversibly, saturably, and with relatively high affinity to receptors in rat testis that are either the same as receptors for hCG and LH or that interact therewith. bTSH, like hCG, is capable of stimulating the production of cAMP in rat Leydig cells, but is much less potent than hCG in this regard. Preparations of crude hCG contain a factor lacking hCG activity in bioassay, immunoassay, and receptor assay that is especially potent in displacing [125I]bTSH from receptors in testis, as has earlier been described for bTSH receptors in bovine thyroid membranes.
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PMID:Binding of bovine thyrotropin to receptors in rat testis and its interaction with gonadotropins. 21 36

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38-amino acid peptide of the glucagon-secretin-vasoactive intestinal polypeptide superfamily. Although PACAP is a potent stimulator of adenylate cyclase activity in the adenohypophysis, the precise target cells for PACAP in the anterior pituitary remain unknown. The aim of the present study was to investigate whether PACAP could stimulate calcium mobilization in individual cells of the pituitary and to determine the type of cells that responded to PACAP. Enzymatically dispersed frog distal pituitary cells were plated on photoetched coverslips and cultured for 3-7 days. The cells were loaded with the fluorescent calcium indicator indo-1, and changes in intracellular calcium concentrations ([Ca2+]i) were monitored using dual wavelength microfluorimetry. The individual cells were localized with the aid of the alpha/numeric grid of the coverslips and identified retrospectively by immunofluorescence. Approximately 45% of GH and PRL cells and 25% of ACTH and TSH cells responded to PACAP (10(-5) M) ejection by an elevation of [Ca2+]i. Only 16% of gonadotropes were stimulated by PACAP. The time course of [Ca2+]i variations showed three different patterns: transient spikes, sustained stimulations, and oscillatory responses. In addition, heterogenous responses were observed within each cell type. These data provide evidence for the involvement of calcium mobilization in the mechanism of action of PACAP on pituitary cells. The results also indicate that in frogs, PACAP may stimulate the secretory activity of GH and PRL cells and, to a lesser extent, ACTH, TSH, and gonadotrope cells.
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PMID:Pituitary adenylate cyclase-activating polypeptide stimulates calcium mobilization in amphibian pituitary cells. 132 48

The effects of GH, PRL, and placental lactogen (PL) on the proliferation of pancreatic beta-cells in vitro were studied as well as the possible effect of insulin-like growth factor-I (IGF-I) in mediating this effect. Proliferating beta-cells were identified by staining with a monoclonal antibody to bromodeoxyuridine (BrdU) after cells were incubated for 1 h in the presence of 10 microM BrdU. By double staining with insulin antibodies it was found that 6.3% of the beta-cells had incorporated BrdU when cultured for 7 days in the presence of 1 microgram/ml human GH (hGH) compared to 0.6% when cultured in the absence of hGH. Similar results were obtained using rat GH. The half-maximal effect of hGH on beta-cell proliferation was observed at 10 ng/ml, and the maximal effect at 100 ng/ml. Islet cells cultured in the presence of PRL or PL caused a dose-dependent increase in beta-cell proliferation similar to that caused by hGH. GH, PRL, and PL had no effect on the proliferation of glucagon- or somatostatin-producing cells. The addition of 100 ng/ml IGF-I to either control or GH-stimulated islet cells did not affect the labeling index. When GH-stimulated proliferation of beta-cells was measured in the presence of neutralizing concentrations of a rabbit IGF-I antiserum, the percentage of beta-cells incorporating BrdU was unaffected. Using Northern blot analysis, no IGF-I transcripts could be detected in RNA from GH-stimulated islets, whereas IGF-I transcripts were readily detected in RNA isolated from rat liver tissue. These data suggest that the stimulatory effect of GH, PRL, and PL on beta-cell proliferation is not mediated by IGF-I, but, rather, is a direct mitogenic effect on the beta-cell.
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PMID:The stimulatory effect of growth hormone, prolactin, and placental lactogen on beta-cell proliferation is not mediated by insulin-like growth factor-I. 167 31

A total of 79 consecutive patients with pituitary tumours were screened for multiple endocrine neoplasia type 1 (MEN-1). The 79 patients included 21 patients with acromegaly, nine with Cushing's disease, 18 with prolactinomas, three with mixed pituitary adenomas (GH and PRL), and 28 patients with no detectable hypersecretion of hormones. The screening consisted of: (1) a family history, (2) a uniform medical history of the patient using a standard questionnaire, and (3) hormonal evaluation including measurements of the serum levels of insulin, gastrin, glucagon, somatostatin, vasoactive intestinal polypeptide and pancreatic polypeptide. Ionized calcium and glucose concentration in serum were also measured. We found no patients with the MEN-1 syndrome. In one patient, we found a transient elevation of serum concentrations of pancreatic polypeptide for which we have no explanation. In another patient, the serum gastrin concentration was elevated secondary to achlorhydria. No other endocrine disorders were found, and no patients had relatives with recognized endocrine pancreatic tumours, primary hyperparathyroidism (HPT), or pituitary adenomas.
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PMID:Screening for multiple endocrine neoplasia type 1 in patients with recognized pituitary adenoma. 198 64

Vasoactive intestinal peptide (VIP) has been implicated as a physiological PRL-releasing factor; however, characterization of VIP receptors on normal pituitaries using radioligand-binding methods has been problematic. In this study we demonstrated specific receptors for VIP in anterior pituitary glands of female rats using HPLC-purified monoiodinated [Tyr(125I)10]VIP. Binding of VIP was reversible, saturable to receptor and radioligand, regulated by guanine nucleotides, and dependent on time and temperature. Scatchard analysis of competitive binding studies indicated high and low affinity binding sites, with equilibrium dissociation constants (Kd) of 0.19 +/- 0.03 and 28 +/- 16 nM, respectively. The corresponding maximum numbers of binding sites were 158 +/- 34 fmol/mg and 11.7 +/- 6.9 pmol/mg. Binding was specific, as peptides with structural homology to VIP were less than 100th as potent as VIP. The rank order of potency of the peptides tested was VIP greater than rat (r) peptide histidine isoleucine = human (h) PHI greater than rGRF greater than bovine GRF = porcine PHI = VIP-(10-28) greater than hGRF greater than secretin greater than apamin greater than glucagon. Radioligand binding was associated primarily with lactotrope-enriched fractions prepared by unit gravity sedimentation of dispersed anterior pituitary cells. VIP stimulated PRL release from cultured rat anterior pituitary cells, with an ED50 of 1 nM. These results, comprising the first identification of specific VIP receptors in normal rat anterior pituitary tissue using radioligand-binding methods, provide additional support for a biological role of VIP in lactotrope function.
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PMID:Receptors for vasoactive intestinal peptide in rat anterior pituitary glands: localization of binding to lactotropes. 215 75

The hormonal regulation of GH receptors was studied by measuring specific binding of [125I]human GH to primary cultured rat hepatocytes. The binding of labeled GH to primary cultured hepatocytes decreased during culture, but addition of dexamethasone (100 nM) compensated for this decrease and even increased GH binding. After addition of dexamethasone, the binding increased to a maximum after 10 h, and after 24 h was about 6 times that of control cells. Glucagon (100 nM) did not have any significant effect on GH binding by itself, but enhanced the increased binding caused by dexamethasone about 1.5-fold. For this effect, glucagon could be replaced by (Bu)2cAMP. Insulin (10 nM) and epidermal growth factor (20 ng/ml) reduced the increase by dexamethasone plus glucagon by about half. Scatchard plot analysis showed that the changes of GH binding induced by various hormones were due to changes in the number of binding sites without significant changes in their affinity. The GH bound to dexamethasone or dexamethasone plus glucagon-treated cells was not replaced by unlabeled ovine PRL. This strongly suggests that the number of somatogenic (GH) receptors may be subject to hormonal regulation: dexamethasone alone or with glucagon may induce GH receptors, whereas insulin and EGF may suppress the induction of GH receptors. These patterns of hormonal regulations were almost the same as those of proteins whose expressions were known to be differentiated functions of liver. On the other hand, the increase of GH binding by dexamethasone was inhibited by cycloheximide and actinomycin D, though the GH binding was inhibited by cycloheximide, but not by actinomycin D in the cells cultured without dexamethasone. This result suggests that the increased binding induced by dexamethasone is dependent on the synthesis of new protein and is probably regulated at a pretranslational level.
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PMID:Hormonal regulation of growth hormone receptors in primary cultured rat hepatocytes. 216 18

GH is necessary but not sufficient to induce adipose differentiation of 3T3-F442A fibroblasts in serum-free medium. Human (h) GH (2 nM) treatment of 3T3-F442A cells in serum-free medium caused a time-dependent (maximal at 48-72 h) and dose-dependent (EC50, approximately 0.2 nM) decrease (40-60%) in de nova protein synthesis. Insulin-like growth factor-I (IGF-I; 17 nM), PRL (2 nM), and glucagon (20 nM) did not decrease de novo protein synthesis, whereas bovine GH was equipotent with hGH. The half-lives of 35S-labeled proteins of 3T3-F442A cells were 21 and 57 h for cells maintained in serum-free medium for 3 days without or with hGH (2 nM), respectively. The total protein content of cells maintained in hGH (2 nM) for 1-4 days was unaffected compared to cells in serum-free medium alone. IGF-I (17 nM) treatment of cells for 4 days doubled the protein content of cells compared to control values in serum-free medium. hGH (2 nM) pretreatment of cells for 1-4 days had no effect on total RNA synthesis. hGH (2 nM) but not IGF-I (17 nM) treatment (3 days) resulted in a 7-fold decrease in cytoplasmic 18S rRNA content (as measured by DNA-RNA hybridization) of cells compared to that of control cells maintained in serum-free medium. When 3T3-F442A cells were transferred to serum-free medium there was a progressive decrease in DNA synthesis. The presence of hGH enhanced the rate at which DNA synthesis decreased for 3T3-F442A cells. IGF-I (17 nM) increased DNA synthesis by 6- and 8-fold after 2 and 3 days of IGF-I exposure. 3T3-F442A cells maintained in serum-free medium for 3 days responded to the addition of platelet-derived growth factor (2 U/ml) and insulin (1.6 microM) with a 56-fold increase in DNA synthesis, assayed 24 h later. 3T3-F442A cells treated with hGH (2 nM) for 3 days before platelet-derived growth factor and insulin addition exhibited a diminished DNA synthetic response, demonstrating that GH-exposed cells were partially refractory to mitogenic stimulation. GH had no effect on any aspect of macromolecular synthesis in 3T3-C2 cells, which have a low frequency of adipogenesis. Based upon these results a cell cycle model for the role of GH in the adipose differentiation of 3T3-F442A cells was proposed.
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PMID:Growth hormone-dependent events in the adipose differentiation of 3T3-F442A fibroblasts: modulation of macromolecular synthesis. 247 29


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