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Štrbák V. Cell Swelling-induced Peptide Hormone Secretion. Cell Physiol Biochem 2011; 28:1155-68. [DOI: 10.1159/000335849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2011] [Indexed: 11/19/2022] Open
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Ethanol and urea affect insulin secretion from islets and insulinoma cells by different mechanisms. Biologia (Bratisl) 2009. [DOI: 10.2478/s11756-009-0149-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Bacová Z, Benický J, Lukyanetz EE, Lukyanetz IA, Strbák V. Different Signaling Pathways Involved in Glucose- and Cell Swelling-Induced Insulin Secretion by Rat Pancreatic Islets in Vitro. Cell Physiol Biochem 2005; 16:59-68. [PMID: 16121034 DOI: 10.1159/000087732] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2005] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The objective was to compare signal transduction pathways exploited by glucose and cell swelling in stimulating insulin secretion. METHODS Isolated rat (Wistar) pancreatic islets were stimulated in vitro by 20 mmol/l glucose or 30% hypotonic medium (202 mOsm/kg) in various experimental conditions. RESULTS Glucose did not stimulate insulin release in calcium free medium. Cell swelling-induced insulin release in calcium free medium, even in the presence of the membrane permeable calcium chelator BAPTA/AM (10 micromol/l). Protein kinase C (PKC) inhibitor bisindolylmaleimide VIII (1 micromol/l) abolished the stimulation of insulin secretion by glucose but did not affect the swelling-induced insulin release. PKC activator phorbol 12-13-dibutyrate (1 micromol/l) stimulated insulin secretion in medium containing Ca2+ and did not potentiate insulin secretion stimulated by hypotonic extracellular fluid. Dilution of the medium (10-30%) had an additive effect on the glucose-induced insulin secretion. Noradrenaline (1 micromol/l) abolished glucose-induced insulin secretion but did not inhibit hypotonic stimulation either in presence or absence of Ca2+. CONCLUSION Glucose- and swelling-induce insulin secretion through separate signal transduction pathways. Hyposmotic stimulation is independent from both the extracellular and intracellular Ca2+, does not involve PKC activation, and could not be inhibited by noradrenaline. These data indicate a novel signaling pathway for stimulation of insulin secretion exploited by cell swelling.
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Affiliation(s)
- Zuzana Bacová
- Institute of Experimental Endocrinology, Centre of Excellence acknowledged by European Commission, Slovak Academy of Sciences, Bratislava, Slovakia
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Cell Volume-Induced Hormone Secretion: Signal Transduction and Specificity. NEUROPHYSIOLOGY+ 2005. [DOI: 10.1007/s11062-005-0059-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Strbák V, Benicky J, Greer SE, Bacova Z, Najvirtova M, Greer MA. Cell swelling-induced peptide hormone secretion. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 559:325-330. [PMID: 18727251 DOI: 10.1007/0-387-23752-6_29] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Cell volume changes induced in various ways (anisosmotic environment, hormones, oxidative stress, substrate uptake) are an integral part of a signal transduction network regulating cell function. Cell swelling has received increasing attention as a stimulus for a variety of intracellular phenomena. One of the most remarkable effects of cell swelling is its powerful effect in inducing exocytosis of material in intracellular secretory vesicles. Secretion of essentially all so-packaged hormones including those from hypothalamus (thyrotropin-releasing hormone, TRH; gonadotropin-releasing hormone, GnRH), pituitary (LH, FSH, ACTH, MSH, TSH, prolactin, beta endorphin), pancreas (insulin, somatostatin, glucagon), heart (atrial natriuretic hormone) and kidney (renin) are stimulated in a concentration-related manner by medium hyposmolarity or isosmolar medium containing permeant molecules such as ethanol or urea (reviewed in Ref. 21). Cell swelling-induced exocytosis is not restricted to endocrine cells and hormones; medium hyposmolarity also induces secretion of exocrine pancreatic enzymes and myeloperoxidase from human polymorphonuclear leukocytes.
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Affiliation(s)
- Vladimir Strbák
- Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava 83306, Slovakia.
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Straub SG, Daniel S, Sharp GWG. Hyposmotic shock stimulates insulin secretion by two distinct mechanisms. Studies with the betaHC9 cell. Am J Physiol Endocrinol Metab 2002; 282:E1070-6. [PMID: 11934672 DOI: 10.1152/ajpendo.00176.2001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exposure of betaHC9 cells to a Krebs-Ringer bicarbonate-HEPES buffer (KRBH) made hypotonic by a reduction of 25 mM NaCl resulted in a prompt stimulation of insulin release. The stimulation was transient, and release rates returned to basal levels after 10 min. The response resembles that of the first phase of glucose-stimulated insulin release. The response did not occur if the reduction in NaCl was compensated for by the addition of an equivalent osmolar amount of sorbitol, so the stimulation of release was due to the osmolarity change and not the reduction in NaCl. The hyposmotic shock released insulin in KRBH with or without Ca(2+). The L-type Ca(2+) channel blocker nitrendipine inhibited the response in normal KRBH but had no effect in KRBH without Ca(2+) despite the latter response being larger than in the presence of extracellular Ca(2+). Similar data were obtained with calciseptine, which also blocks L-type channels. The T-type Ca(2+) channel blocker flunarizine was without effect, as was the chloride channel blocker DIDS. In parallel studies, the readily releasable pool of insulin-containing granules was monitored. Immunoprecipitation of the target-SNARE protein syntaxin and co-immunoprecipitation of the vesicle-SNARE VAMP-2 was used as an indicator of the readily releasable granule pool. After hypotonic shock in the presence of extracellular Ca(2+), the amount of VAMP-2 coimmunoprecipitated by antibodies against syntaxin was much reduced compared with controls. Therefore, under these conditions, hypotonic shock stimulates exocytosis of the readily releasable pool of insulin-containing granules. No such reduction was seen in the absence of extracellular Ca(2+). In conclusion, after reexamination of the effect of hyposmotic shock on insulin secretion in the presence and absence of Ca(2+) (with EGTA in the medium), it is clear that two different mechanisms are operative under these conditions. Moreover, these two mechanisms may be associated with the release of two distinct pools of insulin-containing granules.
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Affiliation(s)
- Susanne G Straub
- Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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Najvirtová M, Baqi L, Kucerová J, Strbák V. Cell swelling induced secretion of TRH by posterior pituitary, hypothalamic paraventricular nucleus and pancreatic islets: effect of L-canavanine. Cell Mol Neurobiol 2002; 22:35-46. [PMID: 12064516 DOI: 10.1023/a:1015389628096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aims of this study were to test if ethanol induces thyrotropin-releasing hormone (TRH) secretion in vitro from the posterior pituitary and hypothalamic explants by a mechanism involving cell swelling, and to characterize the pathway of stimulated secretion. Ethanol, at a concentration of 80 mM, stimulated the release of TRH from the posterior pituitary, the hypothalamic paraventricular nucleus, the median eminence, and the brain septum, when administered only in isosmolar but not in hyperosmolar medium. This indicates the involvement of a cell swelling-inducing mechanism. L-canavanine in a concentration of 3 mM, increased the basal and hyposmosis-induced TRH secretion from the posterior pituitary and the paraventricular nucleus, and both basal and ethanol-induced TRH secretion from isolated pancreatic islets. This indicates the presence of both constitutive and regulatory secretory pathways. Our results suggest that cell swelling induces exocytosis from clathrin coated granules.
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Affiliation(s)
- M Najvirtová
- Laboratory of Neurohumoral Regulations, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava
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Nikodémová M, Greer MA, Strbák V. Hypo-osmolarity stimulates and high sodium concentration inhibits thyrotropin-releasing hormone secretion from rat hypothalamus. Neuroscience 1999; 88:1299-306. [PMID: 10336138 DOI: 10.1016/s0306-4522(98)00279-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The hypothalamic paraventricular nucleus, representing cell bodies in which thyrotropin-releasing hormone is synthesized, and the median eminence, representing nerve terminals, were incubated in vitro. Various hypo- and hyperosmotic solutions were tested to determine osmotic sensitivity of thyrotropin-releasing hormone secretion. High KCl (56 mM) causing membrane depolarization was used as a non-specific control stimulus to induce thyrotropin-releasing hormone secretion. A 30% decrease of medium osmolarity (from 288 to 202 mOsmol/l) increased thyrotropin-releasing hormone secretion from both the paraventricular nucleus and median eminence. A 30% decrease of medium NaCl content by its replacement with choline chloride did not affect basal thyrotropin-releasing hormone secretion. Increasing medium osmolarity with biologically inactive L-glucose did not affect basal or KCl-induced thyrotropin-releasing hormone secretion from either structure. Medium made hyperosmotic (350-450 mOsmol/l) by increasing the NaCl concentration resulted in a dose-dependent decrease of basal thyrotropin-releasing hormone secretion and abolished KCl-induced thyrotropin-releasing hormone secretion. If an osmotically equivalent amount of choline chloride was substituted for NaCl, there was no effect on thyrotropin-releasing hormone secretion, indicating a specific action of Na+. This study indicates a specific sensitivity to high concentrations of Na+ ions of both thyrotropin-releasing hormone-producing parvocellular paraventricular neurons and thyrotropin-releasing hormone-containing nerve terminals in the median eminence.
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Affiliation(s)
- M Nikodémová
- Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovak Republic
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Lang F, Busch GL, Ritter M, Völkl H, Waldegger S, Gulbins E, Häussinger D. Functional significance of cell volume regulatory mechanisms. Physiol Rev 1998; 78:247-306. [PMID: 9457175 DOI: 10.1152/physrev.1998.78.1.247] [Citation(s) in RCA: 1269] [Impact Index Per Article: 48.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To survive, cells have to avoid excessive alterations of cell volume that jeopardize structural integrity and constancy of intracellular milieu. The function of cellular proteins seems specifically sensitive to dilution and concentration, determining the extent of macromolecular crowding. Even at constant extracellular osmolarity, volume constancy of any mammalian cell is permanently challenged by transport of osmotically active substances across the cell membrane and formation or disappearance of cellular osmolarity by metabolism. Thus cell volume constancy requires the continued operation of cell volume regulatory mechanisms, including ion transport across the cell membrane as well as accumulation or disposal of organic osmolytes and metabolites. The various cell volume regulatory mechanisms are triggered by a multitude of intracellular signaling events including alterations of cell membrane potential and of intracellular ion composition, various second messenger cascades, phosphorylation of diverse target proteins, and altered gene expression. Hormones and mediators have been shown to exploit the volume regulatory machinery to exert their effects. Thus cell volume may be considered a second message in the transmission of hormonal signals. Accordingly, alterations of cell volume and volume regulatory mechanisms participate in a wide variety of cellular functions including epithelial transport, metabolism, excitation, hormone release, migration, cell proliferation, and cell death.
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Affiliation(s)
- F Lang
- Institute of Physiology, University of Tübingen, Germany
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Nikodémová M, Weismann P, Filipcik P, Mráz P, Greer MA, Strbák V. Both iso- and hyperosmotic ethanol stimulate release of hypothalamic thyrotropin-releasing hormone despite opposite effect on neuron volume. Neuroscience 1997; 80:1263-9. [PMID: 9284076 DOI: 10.1016/s0306-4522(97)00176-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previous studies have indicated that isosmolar, but not hyperosmolar, ethanol induces in vitro gonadotropin-releasing hormone secretion from the basal hypothalamus, presumably by causing cell swelling. Moreover, ethanol reduces secretion of another hypothalamic neuropeptide vasopressin. We have studied the acute effect of ethanol on specific hypophysiotropic basal and K+-stimulated thyrotropin-releasing hormone secretion in vitro especially in relation to cell swelling. Isosmotic 40-160 mM ethanol increased thyrotropin-releasing hormone release from the hypothalamic paraventricular nucleus and median eminence in a dose-dependent manner. Both a 30% decrease of osmolarity and isosmotic 80 mM ethanol induced 12% swelling of hypothalamic neurons. Hyperosmotic 80 mM or 160 mM ethanol induced release of thyrotropin-releasing hormone from both hypothalamic structures but did not cause cell swelling (80 mM) or even induced cell shrinkage (160 mM). Depletion of medium Ca2+ did not affect thyrotropin-releasing hormone secretion caused by either isosmotic or hyperosmotic ethanol. Our data indicate that both iso- and hyperosmotic ethanol stimulated release of hypophysiotropic thyrotropin-releasing hormone despite opposite effects on neuron volume. The mechanism of ethanol action appears complex and variable depending on the type of cell and neuropeptide affected.
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Affiliation(s)
- M Nikodémová
- Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovak Republic
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Reddy BV, Boyadjieva N, Sarkar DK. Effect of ethanol, propanol, butanol, and catalase enzyme blockers on beta-endorphin secretion from primary cultures of hypothalamic neurons: evidence for a mediatory role of acetaldehyde in ethanol stimulation of beta-endorphin release. Alcohol Clin Exp Res 1995; 19:339-44. [PMID: 7625566 DOI: 10.1111/j.1530-0277.1995.tb01512.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Previously, we have shown that low doses of ethanol (12.5-100 mM) and acetaldehyde (12.5-50 microM), but not salsolinol, enhanced immunoreactive beta-endorphin (IR-beta-EP) secretion from fetal hypothalamic neurons in primary culture. In this study, the effects of ethanol, propanol, and butanol, as well as the effect of catalase inhibitors on IR-beta-EP secretion were studied in vitro to determine the role of membrane fluidization and ethanol metabolism on ethanol-induced IR-beta-EP secretion. The primary cultures of fetal hypothalamic neurons were maintained for 8-9 days in chemically defined medium and treated for 5 hr with ethanol (50 mM), propanol (25 and 50 mM), and butanol (25 and 50 mM). Determination of hourly secretion of IR-beta-EP from the cultures revealed that only 50 mM ethanol caused stimulation of IR-beta-EP secretion, whereas propanol and butanol did not alter IR-beta-EP response at any given concentration. Pretreatment of these cultures with the catalase inhibitors, 3-amino-1,2,4-triazole (3-AT; 1, 5, and 10 mM), caused a dose-dependent inhibition of ethanol-stimulated IR-beta-EP secretion, but did not inhibit dibutyryl cAMP (dcAMP)-stimulated IR-beta-EP secretion. Another catalase inhibitor, sodium azide (5 mM), also inhibited ethanol-stimulated IR-beta-EP secretion. Measurement of acetaldehyde production in cultured cells and media after ethanol or dcAMP treatments revealed that cultured cells produce acetaldehyde only after ethanol treatment and at levels of acetaldehyde (8-24 microM) that are known to evoke IR-beta-EP release. The catalase inhibitor 3-AT (10 mM) treatment reduced ethanol-evoked acetaldehyde production.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B V Reddy
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman 99164-6520, USA
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Sato N, Wang XB, Greer MA. Hormone secretion stimulated by ethanol-induced cell swelling in normal rat adenohypophysial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1991; 260:E946-50. [PMID: 1905486 DOI: 10.1152/ajpendo.1991.260.6.e946] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ethanol has been reported to affect endocrine functions, but its mechanism of action is unclear. To evaluate the hypothesis that cell swelling induced by ethanol permeation through the plasmalemma triggers hormone secretion, we studied the effect of ethanol on both hormone secretion and cell volume in acutely dispersed rat adenohypophysial cells under isotonic and hypertonic conditions. Isotonic ethanol caused a prompt cell swelling and an explosive secretory burst of prolactin and thyrotropin, which were proportional to the concentration of ethanol between 10 and 120 mM. The lowest effective dose of isotonic ethanol was 10 mM, which is below the plasma levels of legal intoxication (16 mM). Removal of medium Ca2+ enhanced the isotonic ethanol-induced increases in both cell volume and secretion. Hypertonic ethanol was ineffective in these effects. These data indicate that, in normal rat adenohypophysial cells, cell swelling caused by the rapid passage of ethanol through the plasmalemma is a potent mechanism for stimulating hormone secretion and this induced secretion is negatively modulated by extracellular Ca2+.
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Affiliation(s)
- N Sato
- Department of Medicine, Oregon Health Sciences University, Portland 97201
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