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Han B, Trew ML, Zgierski-Johnston CM. Cardiac Conduction Velocity, Remodeling and Arrhythmogenesis. Cells 2021; 10:cells10112923. [PMID: 34831145 PMCID: PMC8616078 DOI: 10.3390/cells10112923] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 10/14/2021] [Accepted: 10/22/2021] [Indexed: 02/06/2023] Open
Abstract
Cardiac electrophysiological disorders, in particular arrhythmias, are a key cause of morbidity and mortality throughout the world. There are two basic requirements for arrhythmogenesis: an underlying substrate and a trigger. Altered conduction velocity (CV) provides a key substrate for arrhythmogenesis, with slowed CV increasing the probability of re-entrant arrhythmias by reducing the length scale over which re-entry can occur. In this review, we examine methods to measure cardiac CV in vivo and ex vivo, discuss underlying determinants of CV, and address how pathological variations alter CV, potentially increasing arrhythmogenic risk. Finally, we will highlight future directions both for methodologies to measure CV and for possible treatments to restore normal CV.
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Affiliation(s)
- Bo Han
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, 79110 Freiburg im Breisgau, Germany;
- Faculty of Medicine, University of Freiburg, 79110 Freiburg im Breisgau, Germany
- Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 79104 Freiburg im Breisgau, Germany
- Department of Cardiovascular Surgery, The Fourth People’s Hospital of Jinan, 250031 Jinan, China
| | - Mark L. Trew
- Auckland Bioengineering Institute, University of Auckland, Auckland 1010, New Zealand;
| | - Callum M. Zgierski-Johnston
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, 79110 Freiburg im Breisgau, Germany;
- Faculty of Medicine, University of Freiburg, 79110 Freiburg im Breisgau, Germany
- Correspondence:
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Ke HY, Chin LH, Tsai CS, Lin FZ, Chen YH, Chang YL, Huang SM, Chen YC, Lin CY. Cardiac calcium dysregulation in mice with chronic kidney disease. J Cell Mol Med 2020; 24:3669-3677. [PMID: 32064746 PMCID: PMC7131917 DOI: 10.1111/jcmm.15066] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 01/14/2020] [Accepted: 01/23/2020] [Indexed: 12/30/2022] Open
Abstract
Cardiovascular complications are leading causes of morbidity and mortality in patients with chronic kidney disease (CKD). CKD significantly affects cardiac calcium (Ca2+) regulation, but the underlying mechanisms are not clear. The present study investigated the modulation of Ca2+ homeostasis in CKD mice. Echocardiography revealed impaired fractional shortening (FS) and stroke volume (SV) in CKD mice. Electrocardiography showed that CKD mice exhibited longer QT interval, corrected QT (QTc) prolongation, faster spontaneous activities, shorter action potential duration (APD) and increased ventricle arrhythmogenesis, and ranolazine (10 µmol/L) blocked these effects. Conventional microelectrodes and the Fluo‐3 fluorometric ratio techniques indicated that CKD ventricular cardiomyocytes exhibited higher Ca2+ decay time, Ca2+ sparks, and Ca2+ leakage but lower [Ca2+]i transients and sarcoplasmic reticulum Ca2+ contents. The CaMKII inhibitor KN93 and ranolazine (RAN; late sodium current inhibitor) reversed the deterioration in Ca2+ handling. Western blots revealed that CKD ventricles exhibited higher phosphorylated RyR2 and CaMKII and reduced phosphorylated SERCA2 and SERCA2 and the ratio of PLB‐Thr17 to PLB. In conclusions, the modulation of CaMKII, PLB and late Na+ current in CKD significantly altered cardiac Ca2+ regulation and electrophysiological characteristics. These findings may apply on future clinical therapies.
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Affiliation(s)
- Hung-Yen Ke
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Department and Graduate Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Li-Han Chin
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chien-Sung Tsai
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Department and Graduate Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Feng-Zhi Lin
- Grade institute of life sciences, National Defense Medical Center, Taipei, Taiwan
| | - Yen-Hui Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yung-Lung Chang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Shih-Ming Huang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Yao-Chang Chen
- Department of Biomedical Engineering and Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
| | - Chih-Yuan Lin
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
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Shinozaki Y, Kashiwagi K, Namekata K, Takeda A, Ohno N, Robaye B, Harada T, Iwata T, Koizumi S. Purinergic dysregulation causes hypertensive glaucoma-like optic neuropathy. JCI Insight 2017; 2:93456. [PMID: 28978804 DOI: 10.1172/jci.insight.93456] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 08/24/2017] [Indexed: 12/24/2022] Open
Abstract
Glaucoma is an optic neuropathy characterized by progressive degeneration of retinal ganglion cells (RGCs) and visual loss. Although one of the highest risk factors for glaucoma is elevated intraocular pressure (IOP) and reduction in IOP is the only proven treatment, the mechanism of IOP regulation is poorly understood. We report that the P2Y6 receptor is critical for lowering IOP and that ablation of the P2Y6 gene in mice (P2Y6KO) results in hypertensive glaucoma-like optic neuropathy. Topically applied uridine diphosphate, an endogenous selective agonist for the P2Y6 receptor, decreases IOP. The P2Y6 receptor was expressed in nonpigmented epithelial cells of the ciliary body and controlled aqueous humor dynamics. P2Y6KO mice exhibited sustained elevation of IOP, age-dependent damage to the optic nerve, thinning of ganglion cell plus inner plexiform layers, and a reduction of RGC numbers. These changes in P2Y6KO mice were attenuated by an IOP lowering agent. Consistent with RGC damage, visual functions were impaired in middle-aged P2Y6KO mice. We also found that expression and function of P2Y6 receptors in WT mice were significantly reduced by aging, another important risk factor for glaucoma. In summary, our data show that dysfunctional purinergic signaling causes IOP dysregulation, resulting in glaucomatous optic neuropathy.
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Affiliation(s)
- Youichi Shinozaki
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, and
| | - Kenji Kashiwagi
- Department of Ophthalmology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Kazuhiko Namekata
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Akiko Takeda
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, and
| | - Nobuhiko Ohno
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Bernard Robaye
- Institute of Interdisciplinary Research and.,Institute of Biology and Molecular Medicine, Université Libre de Bruxelles, Belgium
| | - Takayuki Harada
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Takeshi Iwata
- Division of Molecular and Cellular Biology, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, and
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TRIBULOVA N, KNEZL V, SZEIFFOVA BACOVA B, EGAN BENOVA T, VICZENCZOVA C, GONÇALVESOVA E, SLEZAK J. Disordered Myocardial Ca2+ Homeostasis Results in Substructural Alterations That May Promote Occurrence of Malignant Arrhythmias. Physiol Res 2016; 65 Suppl 1:S139-48. [DOI: 10.33549/physiolres.933388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We aimed to determine the impact of Ca2+-related disorders induced in intact animal hearts on ultrastructure of the cardiomyocytes prior to occurrence of severe arrhythmias. Three types of acute experiments were performed that are known to be accompanied by disturbances in Ca2+ handling. Langedorff-perfused rat or guinea pig hearts subjected to K+-deficient perfusion to induce ventricular fibrillation (VF), burst atrial pacing to induce atrial fibrillation (AF) and open chest pig heart exposed to intramyocardial noradrenaline infusion to induce ventricular tachycardia (VT). Tissue samples for electron microscopic examination were taken during basal condition, prior and during occurrence of malignant arrhythmias. Cardiomyocyte alterations preceding occurrence of arrhythmias consisted of non-uniform sarcomere shortening, disruption of myofilaments and injury of mitochondria that most likely reflected cytosolic Ca2+ disturbances and Ca2+ overload. These disorders were linked with non-uniform pattern of neighboring cardiomyocytes and dissociation of adhesive junctions suggesting defects in cardiac cell-to-cell coupling. Our findings identified heterogeneously distributed high [Ca2+]i-induced subcellular injury of the cardiomyocytes and their junctions as a common feature prior occurrence of VT, VF or AF. In conclusion, there is a link between Ca2+-related disorders in contractility and coupling of the cardiomyocytes pointing out a novel paradigm implicated in development of severe arrhythmias.
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Affiliation(s)
- N. TRIBULOVA
- Institute for Heart Research, Slovak Academy of Sciences, Bratislava, Slovak Republic
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Del Rio CL, Clymer BD, Billman GE. Myocardial electrotonic response to submaximal exercise in dogs with healed myocardial infarctions: evidence for β-adrenoceptor mediated enhanced coupling during exercise testing. Front Physiol 2015; 6:25. [PMID: 25698976 PMCID: PMC4318283 DOI: 10.3389/fphys.2015.00025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 01/15/2015] [Indexed: 11/13/2022] Open
Abstract
INTRODUCTION Autonomic neural activation during cardiac stress testing is an established risk-stratification tool in post-myocardial infarction (MI) patients. However, autonomic activation can also modulate myocardial electrotonic coupling, a known factor to contribute to the genesis of arrhythmias. The present study tested the hypothesis that exercise-induced autonomic neural activation modulates electrotonic coupling (as measured by myocardial electrical impedance, MEI) in post-MI animals shown to be susceptible or resistant to ventricular fibrillation (VF). METHODS Dogs (n = 25) with healed MI instrumented for MEI measurements were trained to run on a treadmill and classified based on their susceptibility to VF (12 susceptible, 9 resistant). MEI and ECGs were recorded during 6-stage exercise tests (18 min/test; peak: 6.4 km/h @ 16%) performed under control conditions, and following complete β-adrenoceptor (β-AR) blockade (propranolol); MEI was also measured at rest during escalating β-AR stimulation (isoproterenol) or overdrive-pacing. RESULTS Exercise progressively increased heart rate (HR) and reduced heart rate variability (HRV). In parallel, MEI decreased gradually (enhanced electrotonic coupling) with exercise; at peak exercise, MEI was reduced by 5.3 ± 0.4% (or -23 ± 1.8Ω, P < 0.001). Notably, exercise-mediated electrotonic changes were linearly predicted by the degree of autonomic activation, as indicated by changes in either HR or in HRV (P < 0.001). Indeed, β-AR blockade attenuated the MEI response to exercise while direct β-AR stimulation (at rest) triggered MEI decreases comparable to those observed during exercise; ventricular pacing had no significant effects on MEI. Finally, animals prone to VF had a significantly larger MEI response to exercise. CONCLUSIONS These data suggest that β-AR activation during exercise can acutely enhance electrotonic coupling in the myocardium, particularly in dogs susceptible to ischemia-induced VF.
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Affiliation(s)
- Carlos L Del Rio
- Department of Physiology and Cell Biology, The Ohio State University Columbus, OH, USA ; Department of Electrical and Computer Engineering, The Ohio State University Columbus, OH, USA ; Safety Pharmacology, QTest Labs Columbus, OH, USA
| | - Bradley D Clymer
- Department of Electrical and Computer Engineering, The Ohio State University Columbus, OH, USA ; Biomedical Engineering, The Ohio State University Columbus, OH, USA
| | - George E Billman
- Department of Physiology and Cell Biology, The Ohio State University Columbus, OH, USA ; Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
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Kushnir A, Marks AR. The ryanodine receptor in cardiac physiology and disease. ADVANCES IN PHARMACOLOGY 2010; 59:1-30. [PMID: 20933197 DOI: 10.1016/s1054-3589(10)59001-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
According to the American Heart Association it is estimated that the United States will spend close to $39 billion in 2010 to treat over five million Americans suffering from heart failure. Patients with heart failure suffer from dyspnea and decreased exercised tolerance and are at increased risk for fatal ventricular arrhythmias. Food and Drug Administration -approved pharmacologic therapies for heart failure include diuretics, inhibitors of the renin-angiotensin system, and β-adrenergic receptor antagonists. Over the past 20 years advances in the field of ryanodine receptor (RyR2)/calcium release channel research have greatly advanced our understanding of cardiac physiology and the pathogenesis of heart failure and arrhythmias. Here we review the key observations, controversies, and discoveries that have led to the development of novel compounds targeting the RyR2/calcium release channel for treating heart failure and for preventing lethal arrhythmias.
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Affiliation(s)
- Alexander Kushnir
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY, USA
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Electromechanical characterization of cinnamophilin, a natural thromboxane A2 receptor antagonist with anti-arrhythmic activity, in guinea-pig heart. Br J Pharmacol 2007; 153:110-23. [PMID: 17965733 DOI: 10.1038/sj.bjp.0707541] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Cinnamophilin, a thromboxane A(2) receptor antagonist, has been identified as a prominent anti-arrhythmic agent in rat heart. This study aimed to determine its electromechanical and anti-arrhythmic effects in guinea-pig hearts. EXPERIMENTAL APPROACH Microelectrodes were used to study action potentials in ventricular papillary muscles. Fluo-3 fluorimetric ratio and whole-cell voltage-clamp techniques were used to record calcium transients and membrane currents in single ventricular myocytes, respectively. Intracardiac electrocardiograms were obtained and the anti-arrhythmic efficacy was determined from isolated perfused hearts. KEY RESULTS In papillary muscles, cinnamophilin decreased the maximal rate of upstroke (V(max)) and duration of action potential, and reduced the contractile force. In single ventricular myocytes, cinnamophilin reduced Ca(2+) transient amplitude. Cinnamophilin decreased the L-type Ca(2+) current (I(Ca,L))(IC(50)=7.5 microM) with use-dependency, induced a negative shift of the voltage-dependent inactivation and retarded recovery from inactivation. Cinnamophilin also decreased the Na(+) current (I(Na)) (IC(50)=2.7 microM) and to a lesser extent, the delayed outward (I(K)), inward rectifier (I(K1)), and ATP-sensitive (I(K,ATP)) K(+) currents. In isolated perfused hearts, cinnamophilin prolonged the AV nodal conduction interval and Wenckebach cycle length and the refractory periods of the AV node, His-Purkinje system and ventricle, while shortening the ventricular repolarization time. Additionally, cinnamophilin reduced the occurrence of reperfusion-induced ventricular fibrillation. CONCLUSIONS AND IMPLICATIONS These results suggest that the promising anti-arrhythmic effect and the changes in the electromechanical function induced by cinnamophilin in guinea-pig heart can be chiefly accounted for by inhibition of I(Ca,L) and I(Na).
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Saiz J, Ferrero JM, Monserrat M, Ferrero JM, Thakor NV. Influence of electrical coupling on early afterdepolarizations in ventricular myocytes. IEEE Trans Biomed Eng 1999; 46:138-47. [PMID: 9932335 DOI: 10.1109/10.740876] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Computer modeling is used to study the effect of electrical coupling between a myocardial zone where early afterdepolarizations (EAD's) can develop and the normal neighboring tissue. The effects of such coupling on EAD development and on the likelihood of EAD propagation as an ectopic beat are studied. The influence on EAD formation is investigated by approximating two partially coupled myocardial zones modeled as two active elements coupled by a junctional resistance R. For R values lower than 800 omega cm2, the action potentials are transmitted to the coupled element, and for R values higher than 850 omega cm2 they are blocked. In both ranges of R, when the electrical coupling increases, the EAD's appear at more negative takeoff potentials with higher amplitudes and upstrokes. The EAD's are not elicited if the electrical coupling is too high. In a separate model of two one-dimensional cardiac fiber segments partially coupled by a resistance R, critical R values exist, between 42 and 54 omega cm2, that facilitate EAD propagation. These results demonstrate that in myocardial zones favorable to the formation of EAD, the electrical coupling dramatically affects initiation of EAD and its spread to the neighboring tissue.
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Affiliation(s)
- J Saiz
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.
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Zaugg CE, Wu ST, Lee RJ, Wikman-Coffelt J, Parmley WW. Intracellular Ca2+ handling and vulnerability to ventricular fibrillation in spontaneously hypertensive rats. Hypertension 1997; 30:461-7. [PMID: 9314433 DOI: 10.1161/01.hyp.30.3.461] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Spontaneously hypertensive rats (SHR) with ventricular hypertrophy show an increased vulnerability for the development of potentially lethal ventricular arrhythmias such as ventricular fibrillation (VF). The mechanisms of this increased vulnerability are not fully understood but may be related to abnormal intracellular Ca2+ ([Ca2+]i) handling under stress conditions. We therefore investigated whether [Ca2+]i handling is abnormal in hypertrophied hearts of SHR without heart failure during stimulation stress, and if so whether abnormal [Ca2+]i handling is a determinant of the increased vulnerability to VF in SHR. [Ca2+]i was measured by indo-1 surface fluorescence in perfused hearts of 8- to 10-month-old control Wistar-Kyoto rats (WKY) and age-matched SHR. The state of [Ca2+]i handling was analyzed during three different forms of stimulation stress: rapid pacing, the long rest period after cessation of rapid pacing, and preprogrammed ventricular stimulation that was simultaneously used for the determination of VF threshold. The pulse number VF threshold was used as an index to determine vulnerability to VF and to analyze the relationship of [Ca2+]i handling to vulnerability. Although VF thresholds were lower in SHR than in WKY, we found that both demonstrated similar [Ca2+]i handling during stimulation stress. The extent and rate of [Ca2+]i accumulation during rapid pacing and those of the [Ca2+]i decline after cessation of pacing were similar in SHR and WKY. In addition, the relationship between [Ca2+]i and VF threshold was unaltered in SHR. Thus, we conclude that [Ca2+]i handling is normal in hypertrophied hearts of SHR without heart failure during stimulation stress and that it is not a determinant of the increased vulnerability to VF in SHR.
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Affiliation(s)
- C E Zaugg
- Department of Medicine and Cardiovascular Research Institute, University of California San Francisco, USA
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Abstract
For more than a decade, the inhibition of the renin-angiotensin system in heart failure has been regarded as pure vasodilator therapy. Consequently, the role of the renin-angiotension system has been seen as contributing to hemodynamic overload by vasoconstriction and volume retention. Meanwhile, clinical experience was indicated that important additional aspects of ACE-inhibition in heart failure are attenuation of the enhanced neuroendocrine activity and reversal or prevention of inappropriate trophic reactions of the overloaded myocardium. In overloaded hearts there is enhanced intracardiac formation of angiotensin due to enhanced expression of angiotensinogen and ACE, and due to accumulation of circulating, nephrogenic active renin. In human hearts, a mast-cell-derived chymase, which is not blocked by ACE-inhibition, contributes to intracardiac angiotensin formation. The enhanced intracardiac angiotensin-II formation in overloaded hearts is involved in coronary constriction, impairment of diastolic relaxation, myocyte enlargement and interstitial fibrosis, which aggravate the diastolic impairment. The major problem in overloaded, hypertrophied cardiocytes is the dedifferentiation with instabilization of Ca(++)-homeostasis due to an altered program of gene expression. Dedifferentiated cardiocytes have a reduced expression of sarcoplasmic reticulum Ca(++)-ATPase and an enhanced expression of the sarcolemmal Na+/Ca(++)-exchanger, resulting in an attenuation of active diastole (Ca(++)-reaccumulation into the sarcoplasmic reticulum), a depressed force-frequency relation, and an enhanced susceptibility for fatal arrhythmias. Furthermore, an enhanced local renin-angiotensin system in distensible coronary and systemic arteries seems to contribute to a reduced releasability of endothelium-derived relaxing factor, probably by reducing bradykinin availability. This modulation of endothelial function appears to contribute to the localization and progression of atheroma development in presence of risks factors for atherosclerosis.
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Affiliation(s)
- J Holtz
- Institut für Pathophysiologie, Martin-Luther-Universität, Halle-Wittenberg, FRG
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