51
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Slavikova J, Dvorakova M, Reischig J, Palkovits M, Ondrias K, Tarabova B, Lacinova L, Kvetnansky R, Marks A, Krizanova O. IP3 type 1 receptors in the heart: Their predominance in atrial walls with ganglion cells. Life Sci 2006; 78:1598-602. [PMID: 16223514 DOI: 10.1016/j.lfs.2005.07.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Accepted: 07/22/2005] [Indexed: 11/19/2022]
Abstract
Previously we have shown that inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are abundantly expressed in the atria of rat hearts. Since arrangement of atria is very heterogeneous, in this work we focused on the precise localization of IP3 receptors in the left atrium, where the gene expression of the type 1 IP3R was the highest. The mRNA levels of the IP3 type 1 receptors in the left atrium, left ventricle and myocytes were determined using real-time polymerase chain reaction and Taqman probe. For precise localization, immunohistochemistry with the antibody against type 1 IP3Rs was performed. The mRNA of type 1 IP3 receptor was more than three times higher in the left atrium than in the left ventricle, as determined by real-time PCR. Expression of the type 1 IP3 receptor mRNA was higher in the atria, especially in parts containing cardiac ganglion cells. The atrial auricles, which are particularly free of ganglion cells, and the ventricles (wall of the right and left ventricle and ventricular septum) contained four to five times less IP3 receptors than atrial samples with ganglia. IP3R type 1 immunoreactivity detected by a confocal microscope attributed the most condensed signal on ganglionic cells, although light immunoreactivity was also seen in cardiomyocytes. These results show that type 1IP3 receptors predominate in intrinsic neuronal ganglia of cardiac atria.
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MESH Headings
- Animals
- Calcium Channels/analysis
- Calcium Channels/genetics
- Ganglia, Parasympathetic/chemistry
- Ganglia, Parasympathetic/cytology
- Ganglia, Parasympathetic/metabolism
- Gene Expression
- Heart/innervation
- Heart Atria/innervation
- Immunohistochemistry
- Inositol 1,4,5-Trisphosphate Receptors
- Male
- RNA, Messenger/analysis
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptors, Cytoplasmic and Nuclear/analysis
- Receptors, Cytoplasmic and Nuclear/genetics
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Affiliation(s)
- J Slavikova
- Faculty of Medicine, Charles University, Plzen, Czech Republic
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52
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Lanzafame AA, Turnbull L, Amiramahdi F, Arthur JF, Huynh H, Woodcock EA. Inositol phospholipids localized to caveolae in rat heart are regulated by alpha1-adrenergic receptors and by ischemia-reperfusion. Am J Physiol Heart Circ Physiol 2005; 290:H2059-65. [PMID: 16373581 DOI: 10.1152/ajpheart.01210.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Postischemic reperfusion of rat or mouse hearts causes generation of inositol (1,4,5)trisphosphate [Ins(1,4,5)P3] and the initiation of arrhythmias. In the current study we investigated the possibility that the enhanced Ins(1,4,5)P3 generation in postischemic reperfusion was associated with an increased availability of the precursor lipid phosphatidylinositol(4,5)bisphosphate (PIP2) for alpha1-adrenergic receptor-activated phospholipase C (PLC). Isolated-perfused rat hearts were labeled with [3H]inositol and subjected to ischemia-reperfusion or stimulation with norepinephrine under normoxic conditions. Caveolar fractions were prepared by buoyant density sucrose gradient centrifugation. [3H]PIP2 was concentrated in caveolae, along with Galphaq and PLCbeta1b. Caveolae contained only 27.3 +/- 6.9% (means +/- SE, n = 6) of the total alpha1-adrenergic receptor complement of the heart. These did not migrate to PIP2-containing caveolar fractions with norepinephrine stimulation under normoxic conditions, even though caveolar PIP2 was depleted. In contrast, [3H]PIP2 in caveolae increased during 2 min of reperfusion, independently of norepinephrine release and thus of alpha1-adrenergic receptor activation. The increased PIP2 in the caveolar fractions where signaling proteins are concentrated may be critical for the heightened generation of Ins(1,4,5)P3 in early reperfusion.
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Affiliation(s)
- Alfred A Lanzafame
- Cellular Biochemistry Laboratory, Baker Heart Research Institute, Melbourne, Victoria, Australia
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53
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Ohkusa T. [Involvement of Ca2+ regulatory proteins in lethal arrhythmias]. Nihon Yakurigaku Zasshi 2005; 126:281-6. [PMID: 16327210 DOI: 10.1254/fpj.126.281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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54
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Page RL, Roden DM. Drug therapy for atrial fibrillation: where do we go from here? Nat Rev Drug Discov 2005; 4:899-910. [PMID: 16264433 DOI: 10.1038/nrd1876] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Atrial fibrillation, the most common cardiac arrhythmia requiring medical attention, has effects that range from mild symptoms to devastating stroke. Although treatments have evolved since the foxglove plant (later identified as containing digitalis) was first administered to slow the heart rate, satisfactory drug therapy has not been developed. In this review we describe present-day medical options and developments of future therapies to treat atrial fibrillation and maintain normal sinus rhythm.
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Affiliation(s)
- Richard L Page
- Division of Cardiology, University of Washington School of Medicine, 1959 NE Pacific Street, Room AA502, Health Sciences Bldg, Box 356422, Seattle 98195-6422, USA.
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55
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Vest JA, Wehrens XHT, Reiken SR, Lehnart SE, Dobrev D, Chandra P, Danilo P, Ravens U, Rosen MR, Marks AR. Defective Cardiac Ryanodine Receptor Regulation During Atrial Fibrillation. Circulation 2005; 111:2025-32. [PMID: 15851612 DOI: 10.1161/01.cir.0000162461.67140.4c] [Citation(s) in RCA: 272] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
Ca
2+
leak from the sarcoplasmic reticulum (SR) may play an important role in triggering and/or maintaining atrial arrhythmias, including atrial fibrillation (AF). Protein kinase A (PKA) hyperphosphorylation of the cardiac ryanodine receptor (RyR2) resulting in dissociation of the channel-stabilizing subunit calstabin2 (FK506-binding protein or FKBP12.6) causes SR Ca
2+
leak in failing hearts and can trigger fatal ventricular arrhythmias. Little is known about the role of RyR2 dysfunction in AF, however.
Methods and Results—
Left and right atrial tissue was obtained from dogs with AF induced by rapid right atrial pacing (n=6 for left atrial, n=4 for right atrial) and sham instrumented controls (n=6 for left atrial, n=4 for right atrial). Right atrial tissue was also collected from humans with AF (n=10) and sinus rhythm (n=10) and normal cardiac function. PKA phosphorylation of immunoprecipitated RyR2 was determined by back-phosphorylation and by immunoblotting with a phosphospecific antibody. The amount of calstabin2 bound to RyR2 was determined by coimmunoprecipitation. RyR2 channel currents were measured in planar lipid bilayers. Atrial tissue from both the AF dogs and humans with chronic AF showed a significant increase in PKA phosphorylation of RyR2, with a corresponding decrease in calstabin2 binding to the channel. Channels isolated from dogs with AF exhibited increased open probability under conditions simulating diastole compared with channels from control hearts, suggesting that these AF channels could predispose to a diastolic SR Ca
2+
leak.
Conclusions—
SR Ca
2+
leak due to RyR2 PKA hyperphosphorylation may play a role in initiation and/or maintenance of AF.
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Affiliation(s)
- John A Vest
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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56
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Scoote M, Williams AJ. Myocardial calcium signalling and arrhythmia pathogenesis. Biochem Biophys Res Commun 2004; 322:1286-309. [PMID: 15336976 DOI: 10.1016/j.bbrc.2004.08.034] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Indexed: 11/30/2022]
Abstract
Myocardial calcium signalling is a vital component of the normal physiological function of the heart. Key amongst the many roles calcium plays is its use as the primary signalling component of excitation-contraction coupling, the intracellular process that links cardiomyocyte depolarisation to contraction. Defective cellular calcium handling, due to abnormalities of the various components which mediate and control excitation-contraction coupling, is widely recognised as a significant patho-physiological event in the contractile dysfunction of the failing heart. In addition, similar defects also appear to be increasingly recognised as mediators of certain forms of cardiac arrhythmias. Such defects include single gene defects in excitation-contraction coupling components that lead to inherited sudden death arrhythmia syndromes. Alternatively, arrhythmogenesis occurring within the context of acquired cardiac disease, in particular heart failure, also appears to be highly dependent on abnormal calcium homeostasis. In this article we review the defects in cardiomyocyte calcium homeostasis that lead to particular pro-arrhythmogenic phenomena and discuss recent insights gained into a variety of inherited and acquired arrhythmia syndromes that appear to involve defective calcium signalling as a central component of their patho-physiology. Potential opportunities for new anti arrhythmic therapeutic strategies based on these recent insights are also discussed.
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Affiliation(s)
- Mark Scoote
- Department of Cardiac Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, Dovehouse Street, London SW3 6LY, UK.
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57
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Uemura N, Ohkusa T, Hamano K, Nakagome M, Hori H, Shimizu M, Matsuzaki M, Mochizuki S, Minamisawa S, Ishikawa Y. Down-regulation of sarcolipin mRNA expression in chronic atrial fibrillation. Eur J Clin Invest 2004; 34:723-30. [PMID: 15530144 DOI: 10.1111/j.1365-2362.2004.01422.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Abnormal intracellular Ca2+ homeostasis is an important modulator of chronic atrial fibrillation. Sarcolipin, a homologue of phospholamban, is specifically expressed in the atria, and may play an important role in modulating intracellular Ca2+ homeostasis in the atria. The aim of this study was to investigate the expression of sarcolipin mRNA in the atrial myocardium of patients with chronic atrial fibrillation. METHODS We analyzed the expression of sarcolipin, phospholamban, cardiac calsequestrin and sodium calcium exchanger mRNAs in the right atrial myocardium from nine patients with mitral valvular disease with atrial fibrillation (MVD/AF), nine patients with MVD who had normal sinus rhythm (MVD/NSR), and 10 control patients with normal sinus rhythm who received open heart surgery (controls). The expression of mRNA was measured using the ABI PRISM 7700 Sequence Detection System (Applied Biosystems, Foster City, CA). RESULTS Relative expression levels of sarcolipin mRNA were significantly lower in MVD/AF (0.60 +/- 0.11) than in either MVD/NSR (1.28 +/- 0.17, P < 0.01) or controls (1.10 +/- 0.10, P < 0.05). The expression levels of sarcolipin mRNA were significantly lower in the group with high values for right atrial pressure. The expression levels of phospholamban, cardiac calsequestrin and sodium calcium exchanger mRNAs were comparable among all three groups. CONCLUSIONS Chronic electrical and mechanical overload decreased the expression of sarcolipin mRNA in the right atrial myocardium in patients with chronic atrial fibrillation. Down-regulation of sarcolipin mRNA may be part of atrial fibrillation-induced atrial remodelling.
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Affiliation(s)
- N Uemura
- Department of Physiology, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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58
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Krizanova O, Krepsova K, Micutkova L, Kvetnansky R. Inositol 1,4,5-Trisphosphate Receptors in the Heart Compared to Other Tissues Are Differently Modulated by Stress. Ann N Y Acad Sci 2004; 1018:310-4. [PMID: 15240383 DOI: 10.1196/annals.1296.037] [Citation(s) in RCA: 4] [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
IP(3) receptors are intracellular calcium channels, releasing calcium from the sarcoplasmic reticulum. In the heart, IP(3) receptors of type 1 and 2 were found. These receptors predominate in atria, although they occur also in ventricles, as determined by real-time PCR and Western blot analysis. Single-immobilization stress was found to increase mRNA and/or protein levels of types 1 and 2 IP(3) receptors in cardiac atria. However, in stellate ganglia, which innervate the heart, no changes in the mRNA of the type 1 IP(3) receptors were observed after single-immobilization stress. In adrenal medulla, a moderate decrease in both mRNA and protein levels of IP(3) receptors was observed after single-immobilization exposure. After repeated immobilization, mRNA and protein levels of types 1 and 2 IP(3) receptors decreased significantly in all tested tissues. Our results point to different processing of the single stress in different tissues, while repeated stress results in rapid and significant decrease of the IP(3) receptors.
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Affiliation(s)
- Olga Krizanova
- Institute of Molecular Physiology & Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34 Bratislava, Slovak Republic.
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59
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Zima AV, Blatter LA. Inositol-1,4,5-trisphosphate-dependent Ca(2+) signalling in cat atrial excitation-contraction coupling and arrhythmias. J Physiol 2004; 555:607-15. [PMID: 14754996 PMCID: PMC1664857 DOI: 10.1113/jphysiol.2003.058529] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Inositol-1,4,5-trisphosphate (IP(3))-dependent Ca(2+) release represents the major Ca(2+) mobilizing pathway responsible for diverse functions in non-excitable cells. In the heart, however, its role is largely unknown or controversial. In intact cat atrial myocytes, endothelin (ET-1) increased basal [Ca(2+)](i) levels, enhanced action potential-evoked [Ca(2+)](i) transients, caused [Ca(2+)](i) transients with alternating amplitudes (Ca(2+) alternans), and facilitated spontaneous Ca(2+) release from the sarcoplasmic reticulum (SR) in the form of Ca(2+) sparks and arrhythmogenic Ca(2+) waves. These effects were prevented by the IP(3) receptor (IP(3)R) blocker aminoethoxydiphenyl borate (2-APB), suggesting the involvement of IP(3)-dependent SR Ca(2+) release. In saponin-permeabilized myocytes IP(3) and the more potent IP(3)R agonist adenophostin increased basal [Ca(2+)](i) and the frequency of spontaneous Ca(2+) sparks. In the presence of tetracaine to eliminate Ca(2+) release from ryanodine receptor (RyR) SR Ca(2+) release channels, IP(3) and adenophostin triggered unique elementary, non-propagating IP(3)R-dependent Ca(2+) release events with amplitudes and kinetics that were distinctly different from classical RyR-dependent Ca(2+) sparks. The effects of IP(3) and adenophostin were prevented by heparin and 2-APB. The data suggest that IP(3)-dependent Ca(2+) release increases [Ca(2+)](i) in the vicinity of RyRs and thus facilitates Ca(2+)-induced Ca(2+) release during excitation-contraction coupling. It is concluded that in the adult mammalian atrium IP(3)-dependent Ca(2+) release enhances atrial Ca(2+) signalling and exerts a positive inotropic effect. In addition, by facilitating Ca(2+) release, IP(3) may also be an important component in the development of Ca(2+)-mediated atrial arrhythmias.
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MESH Headings
- Animals
- Arrhythmias, Cardiac/metabolism
- Arrhythmias, Cardiac/physiopathology
- Atrial Function
- Calcium/metabolism
- Calcium Channels/metabolism
- Calcium Signaling/drug effects
- Cats
- Endothelin-1/pharmacology
- Female
- Heart Atria
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors
- Intracellular Membranes/metabolism
- Male
- Myocardium/metabolism
- Myocytes, Cardiac/metabolism
- Osmolar Concentration
- Receptors, Cytoplasmic and Nuclear/metabolism
- Signal Transduction
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Affiliation(s)
- Aleksey V Zima
- Department of Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Ave., Maywood, IL 60153, USA
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60
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Nao T, Ohkusa T, Hisamatsu Y, Inoue N, Matsumoto T, Yamada J, Shimizu A, Yoshiga Y, Yamagata T, Kobayashi S, Yano M, Hamano K, Matsuzaki M. Comparison of expression of connexin in right atrial myocardium in patients with chronic atrial fibrillation versus those in sinus rhythm. Am J Cardiol 2003; 91:678-83. [PMID: 12633797 DOI: 10.1016/s0002-9149(02)03403-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
An abnormal distribution of the gap junction occurs in chronic atrial fibrillation (AF). There are conflicting data regarding changes in connexins (Cxs) in experimental models of AF. We examined whether patients with chronic AF have alterations in atrial Cxs. We analyzed the expression of Cx40 and Cx43 in the right atrial myocardium from 10 patients with mitral valvular disease (MVD) who had AF (MVD/AF), 10 patients with MVD who were in normal sinus rhythm (MVD/NSR), and 10 control patients in NSR (tissue obtained during coronary artery bypass surgery). Hemodynamic and echocardiographic data were obtained before surgery, and an electrophysiologic examination was performed during the operation. An immunohistochemical study was performed on atrial tissue. The relative expression level of Cx40 protein was significantly lower in MVD/AF patients (6.5 +/- 4.6) than in either MVD/NSR patients (17.7 +/- 8.9, p <0.05) or controls (24.7 +/- 11.1, p <0.01). The relative expression level of Cx40 messenger ribonucleic acid was also significantly lower in MVD/AF patients (0.23 +/- 0.13) than in MVD/NSR patients (0.47 +/- 0.26, p <0.01) or controls (0.47 +/- 0.17, p <0.01). For Cx43 protein and messenger ribonucleic acid, there was no significant difference in relative expression levels among the 3 groups. Interestingly, the level of serine-phosphorylated Cx40 was approximately 52% greater in MVD/AF patients than in controls. In MVD/AF patients, the immunoreactive signal of Cx40 was significantly lower than in controls. There was no significant difference in the connective tissue-volume fraction among the groups. Thus, downregulation of Cx40 and abnormal phosphorylation of Cx40 may result in abnormal cell-to-cell communication and alteration in the electrophysiologic properties of the atrium, leading to the initiation and/or perpetuation of AF.
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Affiliation(s)
- Tomoko Nao
- Division of Cardiovascular Medicine, Yamaguchi, Japan
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61
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Lencesova L, Ondrias K, Micutkova L, Filipenko M, Kvetnansky R, Krizanova O. Immobilization stress elevates IP(3) receptor mRNA in adult rat hearts in a glucocorticoid-dependent manner. FEBS Lett 2002; 531:432-6. [PMID: 12435588 DOI: 10.1016/s0014-5793(02)03579-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Gene expression of the type 1 and 2 inositol 1,4,5-trisphosphate (IP(3)) receptors in the rat cardiac atria and ventricles and their possible modulation by single immobilization stress was studied. Single immobilization stress significantly elevated mRNA levels for both types of these receptors. To evaluate the involvement of glucocorticoids in the modulation of the gene expression of IP(3) receptors by immobilization stress, we used adrenalectomized and/or hypophysectomized rats. Since adrenalectomy and/or hypophysectomy completely abolished increase in IP(3) receptor's mRNA levels after the immobilization, we conclude that immobilization stress elevates mRNA of type 1 and 2 IP(3) receptors, mainly through the glucocorticoid responsive element.
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Affiliation(s)
- Lubomira Lencesova
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34, Bratislava, Slovak Republic
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