1
|
Nakipova OV, Averin AS, Kosarsky LS, Ignatiev DA. The Force-Frequency Dependence in the Heart Papillary Muscle of Ground Squirrel as a Reflection of Changes in the Functional State of Animals during the Annual Cycle. Biophysics (Nagoya-shi) 2019. [DOI: 10.1134/s0006350919050191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
2
|
The reduced myofilament responsiveness to calcium contributes to the negative force-frequency relationship in rat cardiomyocytes: role of reactive oxygen species and p-38 map kinase. Pflugers Arch 2017; 469:1663-1673. [DOI: 10.1007/s00424-017-2058-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 08/11/2017] [Indexed: 01/01/2023]
|
3
|
Afanasiev SA, Kondratieva DS, Rebrova TY, Batalov RE, Popov SV. Coupling of the Functional Stability of Rat Myocardium and Activity of Lipid Peroxidation in Combined Development of Postinfarction Remodeling and Diabetes Mellitus. J Diabetes Res 2016; 2016:2548689. [PMID: 26844230 PMCID: PMC4710906 DOI: 10.1155/2016/2548689] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/28/2015] [Accepted: 10/21/2015] [Indexed: 11/18/2022] Open
Abstract
Coupling of the functional stability of rat myocardium and activity of lipid peroxidation processes in combined development of postinfarction remodeling and diabetes mellitus has been studied. The functional stability of myocardium was studied by means of the analysis of inotropic reaction on extrasystolic stimulus, the degree of left ventricular hypertrophy, and the size of scar zone. It was shown that in combined development of postinfarction cardiac remodeling of heart (PICR) with diabetes mellitus (DM) animal body weight decreased in less degree than in diabetic rats. Animals with combined pathology had no heart hypertrophy. The amplitude of extrasystolic contractions in rats with PICR combined with DM had no differences compared to the control group. In myocardium of rats with PICR combined with DM postextrasystolic potentiation was observed in contrast with the rats with PICR alone. The rats with combined pathology had the decreased value of TBA-active products. Thus, the results of study showed that induction of DM on the stage of the development of postinfarction remodeling increases adaptive ability of myocardium. It is manifested in inhibition of increase of LPO processes activity and maintaining of force-interval reactions of myocardium connected with calcium transport systems of sarcoplasmic reticulum of cardiomyocytes.
Collapse
Affiliation(s)
- S. A. Afanasiev
- Federal State Budgetary Scientific Institution “Research Institute for Cardiology”, 111a Kievskaya Street, Tomsk 634012, Russia
| | - D. S. Kondratieva
- Federal State Budgetary Scientific Institution “Research Institute for Cardiology”, 111a Kievskaya Street, Tomsk 634012, Russia
- *D. S. Kondratieva:
| | - T. Yu. Rebrova
- Federal State Budgetary Scientific Institution “Research Institute for Cardiology”, 111a Kievskaya Street, Tomsk 634012, Russia
| | - R. E. Batalov
- Federal State Budgetary Scientific Institution “Research Institute for Cardiology”, 111a Kievskaya Street, Tomsk 634012, Russia
| | - S. V. Popov
- Federal State Budgetary Scientific Institution “Research Institute for Cardiology”, 111a Kievskaya Street, Tomsk 634012, Russia
| |
Collapse
|
4
|
Posnack NG, Brooks D, Chandra A, Jaimes R, Sarvazyan N, Kay M. Physiological response of cardiac tissue to bisphenol A: alterations in ventricular pressure and contractility. Am J Physiol Heart Circ Physiol 2015; 309:H267-75. [PMID: 25980024 DOI: 10.1152/ajpheart.00272.2015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 05/14/2015] [Indexed: 11/22/2022]
Abstract
Biomonitoring studies have indicated that humans are routinely exposed to bisphenol A (BPA), a chemical that is commonly used in the production of polycarbonate plastics and epoxy resins. Epidemiological studies have shown that BPA exposure in humans is associated with cardiovascular disease; however, the direct effects of BPA on cardiac physiology are largely unknown. Previously, we have shown that BPA exposure slows atrioventricular electrical conduction, decreases epicardial conduction velocity, and prolongs action potential duration in excised rat hearts. In the present study, we tested if BPA exposure also adversely affects cardiac contractile performance. We examined the impact of BPA exposure level, sex, and pacing rate on cardiac contractile function in excised rat hearts. Hearts were retrogradely perfused at constant pressure and exposed to 10(-9)-10(-4) M BPA. Left ventricular developed pressure and contractility were measured during sinus rhythm and during pacing (5, 6.5, and 9 Hz). Ca(2+) transients were imaged from whole hearts and from neonatal rat cardiomyocyte layers. During sinus rhythm in female hearts, BPA exposure decreased left ventricular developed pressure and inotropy in a dose-dependent manner. The reduced contractile performance was exacerbated at higher pacing rates. BPA-induced effects on contractile performance were also observed in male hearts, albeit to a lesser extent. Exposure to BPA altered Ca(2+) handling within whole hearts (reduced diastolic and systolic Ca(2+) transient potentiation) and neonatal cardiomyocytes (reduced Ca(2+) transient amplitude and prolonged Ca(2+) transient release time). In conclusion, BPA exposure significantly impaired cardiac performance in a dose-dependent manner, having a major negative impact upon electrical conduction, intracellular Ca(2+) handing, and ventricular contractility.
Collapse
Affiliation(s)
- Nikki Gillum Posnack
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, District of Columbia; and
| | - Daina Brooks
- Department of Biomedical Engineering, School of Engineering and Applied Sciences, The George Washington University, Washington, District of Columbia
| | - Akhil Chandra
- Department of Biomedical Engineering, School of Engineering and Applied Sciences, The George Washington University, Washington, District of Columbia
| | - Rafael Jaimes
- Department of Biomedical Engineering, School of Engineering and Applied Sciences, The George Washington University, Washington, District of Columbia
| | - Narine Sarvazyan
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, District of Columbia; and
| | - Matthew Kay
- Department of Biomedical Engineering, School of Engineering and Applied Sciences, The George Washington University, Washington, District of Columbia
| |
Collapse
|
5
|
Di Carlo MN, Said M, Ling H, Valverde CA, De Giusti VC, Sommese L, Palomeque J, Aiello EA, Skapura DG, Rinaldi G, Respress JL, Brown JH, Wehrens XHT, Salas MA, Mattiazzi A. CaMKII-dependent phosphorylation of cardiac ryanodine receptors regulates cell death in cardiac ischemia/reperfusion injury. J Mol Cell Cardiol 2014; 74:274-83. [PMID: 24949568 PMCID: PMC4131282 DOI: 10.1016/j.yjmcc.2014.06.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 05/22/2014] [Accepted: 06/09/2014] [Indexed: 12/19/2022]
Abstract
Ca(2+)-calmodulin kinase II (CaMKII) activation is deleterious in cardiac ischemia/reperfusion (I/R). Moreover, inhibition of CaMKII-dependent phosphorylations at the sarcoplasmic reticulum (SR) prevents CaMKII-induced I/R damage. However, the downstream targets of CaMKII at the SR level, responsible for this detrimental effect, remain unclear. In the present study we aimed to dissect the role of the two main substrates of CaMKII at the SR level, phospholamban (PLN) and ryanodine receptors (RyR2), in CaMKII-dependent I/R injury. In mouse hearts subjected to global I/R (45/120min), phosphorylation of the primary CaMKII sites, S2814 on cardiac RyR2 and of T17 on PLN, significantly increased at the onset of reperfusion whereas PKA-dependent phosphorylation of RyR2 and PLN did not change. Similar results were obtained in vivo, in mice subjected to regional myocardial I/R (1/24h). Knock-in mice with an inactivated serine 2814 phosphorylation site on RyR2 (S2814A) significantly improved post-ischemic mechanical recovery, reduced infarct size and decreased apoptosis. Conversely, knock-in mice, in which CaMKII site of RyR2 is constitutively activated (S2814D), significantly increased infarct size and exacerbated apoptosis. In S2814A and S2814D mice subjected to regional myocardial ischemia, infarct size was also decreased and increased respectively. Transgenic mice with double-mutant non-phosphorylatable PLN (S16A/T17A) in the PLN knockout background (PLNDM) also showed significantly increased post-ischemic cardiac damage. This effect cannot be attributed to PKA-dependent PLN phosphorylation and was not due to the enhanced L-type Ca(2+) current, present in these mice. Our results reveal a major role for the phosphorylation of S2814 site on RyR2 in CaMKII-dependent I/R cardiac damage. In contrast, they showed that CaMKII-dependent increase in PLN phosphorylation during reperfusion opposes rather than contributes to I/R damage.
Collapse
Affiliation(s)
- Mariano N Di Carlo
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Matilde Said
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Haiyun Ling
- Department of Pharmacology, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0636, USA
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Verónica C De Giusti
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Leandro Sommese
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Darlene G Skapura
- Cardiovascular Research Institute, Department of Molecular Physiology and Biophysics, Department of Medicine (in Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Gustavo Rinaldi
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina
| | - Jonathan L Respress
- Cardiovascular Research Institute, Department of Molecular Physiology and Biophysics, Department of Medicine (in Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Joan Heller Brown
- Department of Pharmacology, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0636, USA
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Department of Molecular Physiology and Biophysics, Department of Medicine (in Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Margarita A Salas
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina.
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, CCT, La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina.
| |
Collapse
|
6
|
Rodriguez JS, Velez Rueda JO, Salas M, Becerra R, Di Carlo MN, Said M, Vittone L, Rinaldi G, Portiansky EL, Mundiña-Weilenmann C, Palomeque J, Mattiazzi A. Increased Na⁺/Ca²⁺ exchanger expression/activity constitutes a point of inflection in the progression to heart failure of hypertensive rats. PLoS One 2014; 9:e96400. [PMID: 24781001 PMCID: PMC4004550 DOI: 10.1371/journal.pone.0096400] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 04/07/2014] [Indexed: 11/19/2022] Open
Abstract
UNLABELLED Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca²⁺-handling alterations are known to occur in SHR. However, the putative modifications of Ca²⁺-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca²⁺, Ca²⁺-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca²⁺ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca²⁺ transient decay and an increase in Na⁺/Ca²⁺ exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca²⁺-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. CONCLUSIONS 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca²⁺ efflux from the cell, constitutes a primary alteration of Ca²⁺-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.
Collapse
Affiliation(s)
- Jesica S. Rodriguez
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - J. Omar Velez Rueda
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Margarita Salas
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Romina Becerra
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Mariano N. Di Carlo
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Matilde Said
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Leticia Vittone
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Gustavo Rinaldi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Enrique L. Portiansky
- Laboratorio de Análisis de Imágenes, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, La Plata, Argentina
| | - Cecilia Mundiña-Weilenmann
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
- * E-mail: (CM-W); (JP)
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
- * E-mail: (CM-W); (JP)
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| |
Collapse
|
7
|
Dvornikov AV, Mi YC, Chan CK. Transient Analysis of Force–Frequency Relationships in Rat Hearts Perfused by Krebs-Henseleit and Tyrode Solutions with Different [Ca2+]o. Cardiovasc Eng Technol 2012. [DOI: 10.1007/s13239-012-0091-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
8
|
Bondke H, Borges AC, Petersen S, Walde T, Baumann G. Non-invasive assessment of myocardial contractility from force-frequency relationship in patients with implanted pacemakers: first results. Europace 2010; 12:968-71. [DOI: 10.1093/europace/euq096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
9
|
Zhang Y, Fraser JA, Schwiening C, Zhang Y, Killeen MJ, Grace AA, Huang CLH. Acute atrial arrhythmogenesis in murine hearts following enhanced extracellular Ca(2+) entry depends on intracellular Ca(2+) stores. Acta Physiol (Oxf) 2010; 198:143-58. [PMID: 19886909 PMCID: PMC3763207 DOI: 10.1111/j.1748-1716.2009.02055.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Aim To investigate the effect of increases in extracellular Ca2+ entry produced by the L-type Ca2+ channel agonist FPL-64176 (FPL) upon acute atrial arrhythmogenesis in intact Langendorff-perfused mouse hearts and its dependence upon diastolic Ca2+ release from sarcoplasmic reticular Ca2+ stores. Methods Confocal microscope studies of Fluo-3 fluorescence in isolated atrial myocytes were performed in parallel with electrophysiological examination of Langendorff-perfused mouse hearts. Results Atrial myocytes stimulated at 1 Hz and exposed to FPL (0.1 μm) initially showed (<10 min) frequent, often multiple, diastolic peaks following the evoked Ca2+ transients whose amplitudes remained close to control values. With continued pacing (>10 min) this reverted to a regular pattern of evoked transients with increased amplitudes but in which diastolic peaks were absent. Higher FPL concentrations (1.0 μm) produced sustained and irregular patterns of cytosolic Ca2+ activity, independent of pacing. Nifedipine (0.5 μm), and caffeine (1.0 mm) and cyclopiazonic acid (CPA) (0.15 μm) pre-treatments respectively produced immediate and gradual reductions in the F/F0 peaks. Such nifedipine and caffeine, or CPA pre-treatments, abolished, or reduced, the effects of 0.1 and 1.0 μm FPL on cytosolic Ca2+ signals. FPL (1.0 μm) increased the incidence of atrial tachycardia and fibrillation in intact Langendorff-perfused hearts without altering atrial effective refractory periods. These effects were inhibited by nifedipine and caffeine, and reduced by CPA. Conclusion Enhanced extracellular Ca2+ entry exerts acute atrial arrhythmogenic effects that is nevertheless dependent upon diastolic Ca2+ release. These findings complement reports that associate established, chronic, atrial arrhythmogenesis with decreased overall inward Ca2+ current.
Collapse
Affiliation(s)
- Y Zhang
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | | | | | | | | | | | | |
Collapse
|
10
|
Kondtratieva DS, Afanasiev SA, Rebrova TY, Tsapko LP, Karpov RS. Rhythmoinotropic myocardial reactions in rats with postinfarction cardiosclerosis against the background of streptozotocin-induced diabetes. Bull Exp Biol Med 2009; 148:181-3. [PMID: 20027322 DOI: 10.1007/s10517-009-0675-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
We studied rhythmoinotropic reactions of the myocardium in rats with postinfarction cardiosclerosis and in rats with postinfarction cardiosclerosis against the background of streptozotocin-induced diabetes. Inotropic myocardial response in rats with postinfarction cardiosclerosis was significantly inhibited after rest periods, while in streptozotocin diabetic rats the rhythmoinotropic myocardial reaction was comparable with the reaction of intact myocardium. The combination of postinfarction cardiosclerosis and diabetes paradoxically contributed to preservation of contractile function of the myocardium in rats.
Collapse
Affiliation(s)
- D S Kondtratieva
- Institute of Cardiology, Tomsk Research Center, Siberian Division of Russian Academy of Medical Sciences, Russia.
| | | | | | | | | |
Collapse
|
11
|
Intraoperative Evaluation von komplexen Mitralklappenrekonstruktionen durch physiologische Provokationstests. ZEITSCHRIFT FUR HERZ THORAX UND GEFASSCHIRURGIE 2009. [DOI: 10.1007/s00398-009-0712-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
12
|
Dilated cardiomyopathy with increased SR Ca2+ loading preceded by a hypercontractile state and diastolic failure in the alpha(1C)TG mouse. PLoS One 2009; 4:e4133. [PMID: 19125184 PMCID: PMC2607013 DOI: 10.1371/journal.pone.0004133] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 11/20/2008] [Indexed: 11/19/2022] Open
Abstract
Mice over-expressing the alpha(1)_subunit (pore) of the L-type Ca2+ channel (alpha(1C)TG) by 4 months (mo) of age exhibit an enlarged heart, hypertrophied myocytes, increased Ca2+ current and Ca2+ transient amplitude, but a normal SR Ca2+ load. With advancing age (8-11 mo), some mice demonstrate advanced hypertrophy but are not in congestive heart failure (NFTG),while others evolve to frank dilated congestive heart failure (FTG). We demonstrate that older NFTG myocytes exhibit a hypercontractile state over a wide range of stimulation frequencies, but maintain a normal SR Ca2+ load compared to age matched non-transgenic (NTG) myocytes. However, at high stimulation rates (2-4 Hz) signs of diastolic contractile failure appear in NFTG cells. The evolution of frank congestive failure in FTG is accompanied by a further increase in heart mass and myocyte size, and phospholamban and ryanodine receptor protein levels and phosphorylation become reduced. In FTG, the SR Ca2+ load increases and Ca2+ release following excitation, increases further. An enhanced NCX function in FTG, as reflected by an accelerated relaxation of the caffeine-induced Ca2+ transient, is insufficient to maintain a normal diastolic Ca2+ during high rates of stimulation. Although a high SR Ca2+ release following excitation is maintained, the hypercontractile state is not maintained at high rates of stimulation, and signs of both systolic and diastolic contractile failure appear. Thus, the dilated cardiomyopathy that evolves in this mouse model exhibits signs of both systolic and diastolic failure, but not a deficient SR Ca2+ loading or release, as occurs in some other cardiomyopathic models.
Collapse
|