Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The secretion of growth hormone (GH) is governed by the remarkably complex interaction of neural and feedback regulatory components. The net result is a striking pulsatile pattern of GH release evident in every mammalian species studied so far. Extensive experimental evidence indicates that the episodic pattern of GH release from the pituitary gland is generated by a delicate interplay between at least two hypothalamic hormones--a stimulatory GH-releasing factor (GRF) and an inhibitory hormone, somatostatin (SRIF). This paper will focus on the interrelation of GRF and SRIF, and on the modulatory influence of GH and insulin-like growth factor (IGF) feedback, in the genesis of episodic GH secretion.
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PMID:Genesis of episodic growth hormone secretion. 792 Sep 94

Rats were administered the somatostatin analogue octreotide 15 micrograms intraperitoneally twice daily for 4 weeks after intraportal injection of somatostatin receptor-positive pancreatic tumour cells (CA-20948) and somatostatin receptor-negative colonic tumour cells (CC531). Octreotide significantly inhibited the growth and development of somatostatin receptor-positive tumour cells in the liver. The median number of liver tumours was 286 (range 146 to greater than 500) in the treated animals and more than 500 (range 250 to in excess of 500) in the controls (P < 0.05). This significant difference in tumour load was also represented in the mean(s.e.m.) liver weight (14.5(3.7) g in animals given octreotide versus 17.9(3.0) g in the controls). No effect of octreotide treatment was found on the growth and development of somatostatin receptor-negative tumour cells in the liver. The median (range) number of tumours was 6.5 (0-425) in the treated animals and 11.0 (0-475) in the controls. Mean(s.e.m.) liver weights were 14.0(5.7) g and 11.8(4.5) g respectively. There was no difference in serum levels of growth hormone, prolactin and insulin-like growth factor between control and octreotide-treated rats. The growth inhibition of somatostatin receptor-positive tumour cells was unlikely to be the result of suppressed secretion of one of these tumour growth factors. Octreotide may be useful for the treatment of patients with somatostatin receptor-positive hepatic metastases, which can be demonstrated by somatostatin receptor scintigraphy.
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PMID:Somatostatin receptor-dependent growth inhibition of liver metastases by octreotide. 795 4

Availability of recombinant growth hormone (GH) and development of long-acting formulations of this material will undoubtedly lead to widespread use of GH in animal industry and in medicine. GH can act, directly or indirectly, on multiple targets, but its influence on the reproductive system and on the hormonal control of reproduction is poorly understood. Overexpression of GH genes in transgenic animals provides a unique opportunity to study the effects of long-term GH excess. Transgenic mice overexpressing bovine, ovine, or rat GH (hormones with actions closely resembling, if not identical to, those of endogenous [mouse] GH), exhibit enhancement of growth, increased adult body size, and reduced life-span as well as a number of endocrine and reproductive abnormalities. Ectopic overexpression of bovine GH (bGH) driven by metallothionein or phosphoenolpyruvate carboxykinase promoters is associated with altered activity of hypothalamic neurons which produce somatostatin, loss of adenohypophyseal GH releasing hormone (GHRH) receptors, and suppression of endogenous (mouse) GH release. Elevation of plasma levels of GH (primarily bGH) and insulin-like growth factor (IGF-I) in these transgenic mice leads to increases in the number of hepatic GH and prolactin (PRL) receptors, in the serum levels of GH-binding protein (GHBP), in the percent of GHBP complexed with GH, and in the circulating insulin levels. In addition, plasma adrenocorticotropic hormone (ACTH) and corticosterone levels are elevated. Plasma levels of luteinizing hormone (LH), as well as its synthesis and release, are not consistently affected, but follicle-stimulating hormone (FSH) levels are suppressed, apparently due to pre- and post-translational effects. Pituitary lactotrophs exhibit characteristics of chronic enhancement of secretory activity, and plasma PRL levels are elevated. Prolactin responses to mating or to pharmacological blockade of dopamine synthesis are abnormal. Reproductive life span and efficiency are reduced in both sexes, with the severity and frequency of reproductive deficits being related to plasma bGH levels. Most transgenic females expressing high levels of bGH are sterile due to luteal failure. Overexpression of human GH which, in the mouse, interacts with both GH and PRL receptors leads to additional endocrine and reproductive abnormalities including stimulation of LH beta mRNA levels and LH secretion, loss of responsiveness to testosterone feedback, overstimulation of mammary glands, enhanced mammary tumorigenesis, and hypertrophy of accessory reproductive glands in males.
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PMID:Neuroendocrine and reproductive consequences of overexpression of growth hormone in transgenic mice. 807 44

Acromegaly is most often associated with a pituitary somatotroph adenoma. While multiple lines of evidence suggest an intrinsic somatic cell defect in adenoma formation, the role of hypothalamic hormones in pituitary tumorigenesis remains unclear. We describe the functional and morphological features of the pituitary of a patient with a long-standing ectopic GH-releasing hormone (GHRH)-producing tumor and acromegaly. This 28-yr-old woman with a documented 10-yr history of a disseminated bronchial carcinoid was evaluated for clinical features of acromegaly. Elevated serum GH (88 micrograms/L) was not suppressed after glucose ingestion and was paradoxically stimulated by TRH, but did not respond to GHRH or GnRH administration. Serum insulin-like growth factor-1 (730 micrograms/L; normal, < 333 micrograms/L), insulin-like growth factor-binding protein-3 (9.5 mg/L; normal, 2-4.2 mg/L), and GHRH (26.1 micrograms/L; normal, < 20 ng/L) were elevated. Magnetic resonance imaging revealed a diffusely enlarged pituitary gland. Octreotide treatment for 4 months resulted in suboptimal clinical and biochemical responses. Examination of the transsphenoidally resected pituitary by light microscopy revealed diffuse somatotroph hyperplasia, with intact reticulin network and preservation of the acinar architecture. Electron microscopy showed active somatotrophs interspersed with other cell types. In situ hybridization revealed very strong positivity for GH mRNA, whereas fewer cells contained GHRH and somatostatin mRNA signals. Dispersed pituitary cells secreted GH into culture medium. GH release was stimulated by GHRH and GHRH plus TRH, but not by TRH alone; GH was suppressed by octreotide in vitro. We conclude that sustained exposure to ectopic GHRH leads to somatotroph hyperplasia, but, at least in this case, was not sufficient for adenomatous transformation.
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PMID:Somatotroph hyperplasia without pituitary adenoma associated with a long standing growth hormone-releasing hormone-producing bronchial carcinoid. 812 26

The purpose of this study was to determine whether the long-acting somatostatin analog SMS 201-995 (octreotide) shrinks growth hormone (GH)-secreting adenomas and improves the results of subsequent transsphenoidal surgery. Ten previously untreated active acromegalic patients (nine women and one man) with invasive tumors were treated with SMS 201-995 (100 micrograms subcutaneously every 8 hours) for 6 weeks prior to transsphenoidal surgery. The clinical activity, mean GH secretion, insulin-like growth factor (IGF)-I concentration, and tumor volume were measured under basal conditions and on Days 14, 28, and 42 of treatment. The SMS 201-995 improved the symptoms of acromegaly in all patients. Mean levels of both GH and IGF-I (+/- standard deviation) were significantly decreased by Day 14 (from 92.9 +/- 30.5 to 44.9 +/- 20.3 micrograms/liter and from 10.6 +/- 7.4 to 5.9 +/- 2.6 U/ml, respectively), after which there were only slight further decreases. Six (60%) of the 10 patients experienced tumor shrinkage ranging from 9% to 78% (mean 30%). When it occurred, tumor shrinkage was significant by Day 14 (7.9 +/- 6.3 to 6.5 +/- 5.1 cu cm) and no further shrinkage was achieved by longer administration. Transsphenoidal surgery reduced postoperative GH levels to less than 2 micrograms/liter and IGF-I to less than 1.5 U/ml in six patients (60%). This percentage of cure is higher than expected from the literature and the authors' previous experience. However, an investigation of the influence of this drug on several parameters, such as reduction of tumor size or GH and IGF-I concentrations, has failed to prove any relationship. Only pretreatment size of the tumor was of predictive value with respect to the surgical outcome.
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PMID:Treatment of invasive growth hormone pituitary adenomas with long-acting somatostatin analog SMS 201-995 before transsphenoidal surgery. 820 9

Among somatostatin analogues, octreotide is the most extensively studied. Its pharmacodynamic properties are similar to those of somatostatin, with a wide spectrum of inhibitory effects on anterior pituitary function, pancreas and gut endocrine secretions, and gastrointestinal functions. Compared with the somatostatin, octreotide is highly resistant to enzymatic degradation and has a prolonged plasma half-life of about 100 minutes in humans, allowing its use in the long term treatment of various pathological conditions. Differential effects of octreotide on endocrine secretions such as growth hormone (GH) and insulin in healthy volunteers, as well as variable efficacy in the treatment of endocrine tumours, may relate to the distribution of somatostatin receptor subtypes. The volume of distribution of octreotide ranges from 18 to 30L. Calculated serum distribution half-life ranges from 72 to 98 minutes. In blood, octreotide is mainly distributed in the plasma, 65% being bound to lipoproteins. After subcutaneous injection, absorption appears rapid and complete and bioavailability is about 100%. Mean peak plasma concentrations are between 2 and 4 micrograms/L in patients receiving 50 to 100 micrograms. Peak concentrations are reached within 20 to 30 minutes and are 20 to 40% of corresponding values after intravenous injection. Peak concentrations and values for areas under the plasma concentration-time curve linearly correlate with the dosage. The elimination half-life is about 90 to 110 minutes. Total clearance in healthy individuals is about 160 ml/min (9.6 L/h). Hepatic metabolism of octreotide is extensive (30 to 40%) and about 11 to 20% of the dose is excreted unchanged in the urine. Among pituitary tumours, GH- and thyrotrophin-secreting adenomas are the most sensitive to octreotide. Octreotide has been widely used in the treatment of acromegaly. 50 to 80% of the patients respond to daily multiple subcutaneous injections with insulin-like growth factor-1 (IGF1) levels being normalised in about 40 to 50% of them. Neither desensitisation with long term therapy nor rebound phenomena after octreotide withdrawal have been noticed in these studies. Even in patients with partial response, clinical symptoms improved. Octreotide daily dosages needed to achieve optimum responses may vary greatly from one patient to another. In a minority of patients complete resistance to octreotide was observed and was not always related to the absence of somatostatin receptors in the tumour. The wide spectrum of effects of octreotide in humans accounts for adverse effects seen during long term treatment, primarily cholelithiasis. Other modes of administration are efficient.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Clinical pharmacokinetics of octreotide. Therapeutic applications in patients with pituitary tumours. 828 33

Growth hormone (GH), insulin-like growth factor-1 (IGF-1) and prolactin (PRL) in blood and urine were observed in 20 patients with acromegaly in a double-blind placebo-controlled 14-day clinical trial with the somatostatin analog octreotide. Hormones were determined by the same radioimmunoassays in blood and urine. Significant reduction of GH and IGF-1 during octreotide treatment compared to placebo was seen in blood but not in urine. Patients with diabetes mellitus, 2 of the 20 patients, showed notably increased urinary GH and IGF-1 in relation to blood levels. Therefore, results without the two diabetic patients were calculated, showing significant reduction of urinary GH and IGF-I during treatment on some, but not all observation days. The intraindividual variations of GH and IGF-1 were greater in urine than in blood. PRL levels were not significantly affected by octreotide either with or without the two diabetic patients. In conclusion, this study indicates, that GH and IGF-1 in blood are preferable to urinary GH and IGF-1 as response markers during treatment of acromegaly with octreotide. One disadvantage with urinary assessments of GH and IGF-1 in acromegaly seems to be the relatively higher excretion in patients with diabetes mellitus.
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PMID:Growth hormone and insulin-like growth factor-1 in blood and urine as response markers during treatment of acromegaly with octreotide: a double-blind placebo-controlled study. 851 80

It has recently been demonstrated in various clinical experiments that native somatostatin and its long-acting analogues increase circulating levels of insulin-like growth factor-binding protein-1 (IGFBP-1) within 1-2 h, independent of effects on circulating insulin or glucose levels. Using human hepatoma cells in vitro the somatostatin analogue, octreotide, has been shown to increase IGFBP-1 mRNA within 24 h indicative of a direct stimulatory effect of octreotide on IGFBP-1 synthesis. In order to ascertain whether octreotide acutely stimulates IGFBP-1 mRNA in vivo, placebo or two doses of octreotide were injected subcutaneously into three groups of rats. One hour after saline or octreotide administration, liver, kidney and serum were obtained for the measurement of IGFBPs-1 to -6 mRNA in tissue and IGFBPs and IGF-I in serum. Octreotide increased liver IGFBP-1 (562%) and IGFBP-3 (23%) mRNA expression with a concomitant rise in the circulating 30 kDa (106%) and 38-42 kDa (23%) IGFBPs. No detectable changes were seen in other liver IGFBP transcripts, other circulating IGFBPs or in any of the kidney IGFBP transcripts. Serum IGF-I increased by 37% in the animals receiving the high octreotide dose. No concomitant changes were observed in glucose or insulin levels. These data show that octreotide acutely stimulates hepatic IGFBP-1 and -3 mRNA in vivo in rats. The stimulating effect on IGFBP-3 presents a possible hitherto unknown form of regulation of IGFBP-3 whilst the effect on IGFBP-1 indicates that the stimulatory effect of octreotide on circulating IGFBP-1 described in clinical trials may be due to increased hepatic production. The present findings may be of importance in the clinical use of octreotide.
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PMID:Stimulation of hepatic insulin-like growth factor-binding protein-1 and -3 gene expression by octreotide in rats. 854 25

As growth hormone (GH) and insulin-like growth factor type I (IGF-I) have been suggested to be involved in the development of some proliferative ocular disorders, we investigated the eventual antiproliferative properties of a long acting somatostatin analogue, somatuline or BIM23014 (IPSEN Biotech, France), in an original model of experimental proliferative vitreoretinopathy. Two studies were separately done to investigate respective effects of subcutaneously- and intravitreally administered somatuline. Injections of 10(7) human platelets freshly prepared from a unique normal donor were injected into the vitreous, cavity of pigmented rabbits. The first experiment consisted of evaluating vitreoretinal proliferation in 17 eyes from rabbits receiving subcutaneous injections of 25 micrograms/kg of BIM23014, given twice a day, from the day after injection for one month. A group of 14 eyes served as non treated controls. The second experiment was conducted in 33 eyes: 10 received intravitreally 1 microgram of somatuline given once a week for one month, 10 eyes similarly received 5 micrograms/week of somatuline, the remaining 13 eyes serving as controls with intravitreal injections of sterile saline. All animals were examined ophthalmoscopically twice a week for one month in a masked manner, and sacrificed at the end of the experiment for histological and immunohistological analyses. In all but two eyes from the subcutaneously treated group, intravitreal and preretinal membranes formed, five to eight days after platelet injection. Intravitreal proliferation progressively increased, resulting in various degrees of vitreoretinal retraction and retinal detachment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evaluation of antiproliferative effects of the somatostatin analogue somatuline in a rabbit model of traction retinal detachment. 856 35

Angiopeptin is a long-acting cyclic octapeptide with pharmacologic actions clearly resembling those of the natural hormone somatostatin, but with different binding affinities for the five known somatostatin receptors. It is a potent inhibitor of myointimal migration and proliferation in animal models of angioplasty and organ transplantation. Experimentally, angiopeptin inhibits transplant arteriosclerosis in cardiac, renal and vascular allografts. The mechanisms are thought to involve abrogation of the increase of insulin-like growth factor (IGF-I) and other growth factors that occur in the vascular wall following immune or mechanical injury. Angiopeptin also restores the endothelium-dependent vasodilatory response to acetylcholine. Clinically, angiopeptin is safe in cardiac transplant patients and shows promise in inhibiting coronary transplant arteriosclerosis. Furthermore, in large clinical trials, angiopeptin (given as a continuous infusion for 5 days) inhibits serious clinical events, such as myocardial infarction, death and revascularization at 6 and 12 months following percutaneous transluminal coronary angioplasty. It has few serious side effects.
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PMID:Angiopeptin: experimental and clinical studies of inhibition of myointimal proliferation. 858 76


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