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Milan HFM, Almazloum AA, Bassani RA, Bassani JWM. Membrane polarization at the excitation threshold induced by external electric fields in cardiomyocytes of rats at different developmental stages. Med Biol Eng Comput 2023; 61:2637-2647. [PMID: 37405671 DOI: 10.1007/s11517-023-02868-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 06/07/2023] [Indexed: 07/06/2023]
Abstract
External electric fields (E), used for cardiac pacing and defibrillation/cardioversion, induce a spatially variable change in cardiomyocyte transmembrane potential (ΔVm) that depends on cell geometry and E orientation. This study investigates E-induced ΔVm in cardiomyocytes from rats at different ages, which show marked size/geometry variation. Using a tridimensional numerical electromagnetic model recently proposed (NM3D), it was possible: (a) to evaluate the suitability of the simpler, prolate spheroid analytical model (PSAM) to calculate amplitude and location of ΔVm maximum (ΔVmax) for E = 1 V.cm-1; and (b) to estimate the ΔVmax required for excitation (ΔVT) from experimentally determined threshold E values (ET). Ventricular myocytes were isolated from neonatal, weaning, adult, and aging Wistar rats. NM3D was constructed as the extruded 2D microscopy cell image, while measured minor and major cell dimensions were used for PSAM. Acceptable ΔVm estimates can be obtained with PSAM from paralelepidal cells for small θ. ET, but not ΔVT, was higher for neonate cells. ΔVT was significantly greater in the cell from older animals, which indicate lower responsiveness to E associated with aging, rather than with altered cell geometry/dimensions. ΔVT might be used as a non-invasive indicator of cell excitability as it is little affected by cell geometry/size.
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Affiliation(s)
- Hugo F M Milan
- Department of Electronics and Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Cidade Universitária Zeferino Vaz, Av. Albert Einstein 400, Campinas, SP, 13083-852, Brazil.
| | - Ahmad A Almazloum
- Department of Electronics and Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Cidade Universitária Zeferino Vaz, Av. Albert Einstein 400, Campinas, SP, 13083-852, Brazil
| | - Rosana A Bassani
- Department of Electronics and Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Cidade Universitária Zeferino Vaz, Av. Albert Einstein 400, Campinas, SP, 13083-852, Brazil
- LabNECC, Center for Biomedical Engineering (CEB), University of Campinas (UNICAMP), R. Alexander Fleming 163, Cidade Universitária Zeferino Vaz, Campinas, SP, 13083-881, Brazil
| | - José W M Bassani
- Department of Electronics and Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Cidade Universitária Zeferino Vaz, Av. Albert Einstein 400, Campinas, SP, 13083-852, Brazil
- LabNECC, Center for Biomedical Engineering (CEB), University of Campinas (UNICAMP), R. Alexander Fleming 163, Cidade Universitária Zeferino Vaz, Campinas, SP, 13083-881, Brazil
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Salameh S, Ogueri V, Posnack NG. Adapting to a new environment: postnatal maturation of the human cardiomyocyte. J Physiol 2023; 601:2593-2619. [PMID: 37031380 PMCID: PMC10775138 DOI: 10.1113/jp283792] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 03/16/2023] [Indexed: 04/10/2023] Open
Abstract
The postnatal mammalian heart undergoes remarkable developmental changes, which are stimulated by the transition from the intrauterine to extrauterine environment. With birth, increased oxygen levels promote metabolic, structural and biophysical maturation of cardiomyocytes, resulting in mature muscle with increased efficiency, contractility and electrical conduction. In this Topical Review article, we highlight key studies that inform our current understanding of human cardiomyocyte maturation. Collectively, these studies suggest that human atrial and ventricular myocytes evolve quickly within the first year but might not reach a fully mature adult phenotype until nearly the first decade of life. However, it is important to note that fetal, neonatal and paediatric cardiac physiology studies are hindered by a number of limitations, including the scarcity of human tissue, small sample size and a heavy reliance on diseased tissue samples, often without age-matched healthy controls. Future developmental studies are warranted to expand our understanding of normal cardiac physiology/pathophysiology and inform age-appropriate treatment strategies for cardiac disease.
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Affiliation(s)
- Shatha Salameh
- Department of Pharmacology & Physiology, George Washington University, Washington, DC, USA
- Sheikh Zayed Institute for Pediatric Surgical Innovation, Children’s National Hospital, Washington, DC, USA
| | - Vanessa Ogueri
- Children’s National Heart Institute, Children’s National Hospital, Washington, DC, USA
| | - Nikki Gillum Posnack
- Department of Pharmacology & Physiology, George Washington University, Washington, DC, USA
- Sheikh Zayed Institute for Pediatric Surgical Innovation, Children’s National Hospital, Washington, DC, USA
- Children’s National Heart Institute, Children’s National Hospital, Washington, DC, USA
- Department of Pediatrics, George Washington University, Washington, DC, USA
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Oshiyama NF, Pereira AHM, Cardoso AC, Franchini KG, Bassani JWM, Bassani RA. Developmental differences in myocardial transmembrane Na + transport: Implications for excitability and Na + handling. J Physiol 2022; 600:2651-2667. [PMID: 35489088 DOI: 10.1113/jp282661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 04/20/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Previous studies showed that myocardial preparations from immature rats are less sensitive to electrical field stimulation than adult preparations. Freshly-isolated ventricular myocytes from neonatal rats showed lower excitability than adult cells, e.g., less negative threshold membrane potential and greater membrane depolarization required for action potential triggering. In addition to differences in mRNA levels for Na+ channels isoforms and greater Na+ current (INa ) density, Na+ channel voltage-dependence was shifted to the right in immature myocytes, which seems to be sufficient to decrease excitability, according to computer simulations. Only in neonatal myocytes did cyclic activity promote marked cytosolic Na+ accumulation, which was prevented by abolition of systolic Ca2+ transients by blockade of Ca2+ currents. Developmental changes in INa may account for the difference in action potential initiation parameters, but not for cytosolic Na+ accumulation, which seems to be due mainly to Na+ /Ca2+ exchanger-mediated Na+ influx. ABSTRACT Little is currently known about possible developmental changes in myocardial Na+ handling, which may have impact on cell excitability and Ca2+ content. Resting intracellular Na+ concentration ([Na+ ]i ), measured in freshly-isolated rat ventricular myocytes with CoroNa-green, was not significantly different in neonates (3-5 days old) and adults, but electrical stimulation caused marked [Na+ ]i rise only in neonates. Inhibition of L-type Ca2+ current by CdCl2 abolished not only systolic Ca2+ transients, but also activity-dependent intracellular Na+ accumulation in immature cells. This indicates that the main Na+ influx pathway during activity is the Na+ /Ca2+ exchanger, rather than voltage-dependent Na+ current (INa ), which was not affected by CdCl2 . In immature myocytes, INa density was 2-fold greater, inactivation was faster, and the current peak occurred at less negative transmembrane potential (Em ) than in adults. Na+ channel steady-state activation and inactivation curves in neonates showed a rightward shift, which should increase channel availability at diastolic Em , but also require greater depolarization for excitation, which was observed experimentally and reproduced in computer simulations. Ventricular mRNA levels of Nav 1.1, Nav 1.4 and Nav 1.5 pore-forming isoforms were greater in neonate ventricles, while decrease was seen for the β1 subunit. Both molecular and biophysical changes in the channel profile may contribute to the differences in INa density and voltage-dependence, and also to the less negative threshold Em in neonates, compared to adults. The apparently lower excitability in immature ventricle may confer protection against the development of spontaneous activity in this tissue. Abstract figure legend Little is currently known about possible developmental changes in myocardial Na+ transport, which may have impact on cell excitability and other physiological aspects. At the mRNA level, neonatal rat ventricle expresses a greater variety of Na+ channel isoforms than in adults. In immature ventricular cardiomyocytes, Na+ current (INa ) density was greater, but voltage-dependence is shifted to less negative potentials than in adults. This should increase channel availability at diastolic membrane potential, but also require greater depolarization for excitation, which was observed experimentally and reproduced in computer simulation. We also observed that electrical stimulation caused marked intracellular Na+ accumulation only in neonates, which was abolished when Ca2+ transients and the Na+ /Ca2+ exchanger (NCX) were inhibited by Cd2+ + Ni2+ . Thus, it seems that the main Na+ influx pathway during activity in neonates is the NCX, rather than voltage-dependent INa , which was not affected by these blockers. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Natália F Oshiyama
- Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas, Campinas, SP, Brazil.,National Laboratory for Cell Calcium Study, (LabNECC), Center for Biomedical Engineering, University of Campinas, Campinas, SP, Brazil
| | - Ana H M Pereira
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (LNBio/CNPEM), Campinas, SP, Brazil
| | - Alisson C Cardoso
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (LNBio/CNPEM), Campinas, SP, Brazil
| | - Kleber G Franchini
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (LNBio/CNPEM), Campinas, SP, Brazil.,Department of Internal Medicine, School of Medicine, University of Campinas, Campinas, SP, Brazil
| | - José W M Bassani
- Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas, Campinas, SP, Brazil.,National Laboratory for Cell Calcium Study, (LabNECC), Center for Biomedical Engineering, University of Campinas, Campinas, SP, Brazil
| | - Rosana A Bassani
- Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas, Campinas, SP, Brazil.,National Laboratory for Cell Calcium Study, (LabNECC), Center for Biomedical Engineering, University of Campinas, Campinas, SP, Brazil
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Sources of Ca 2+ for contraction of the heart tube of Tenebrio molitor (Coleoptera: Tenebrionidae). J Comp Physiol B 2018; 188:929-937. [PMID: 30218147 DOI: 10.1007/s00360-018-1183-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 09/06/2018] [Indexed: 10/28/2022]
Abstract
Insect and vertebrate hearts share the ability to generate spontaneously their rhythmic electrical activity, which triggers the fluid-propelling mechanical activity. Although insects have been used as models in studies on the impact of genetic alterations on cardiac function, there is surprisingly little information on the generation of the inotropic activity in their hearts. The main goal of this study was to investigate the sources of Ca2+ for contraction in Tenebrio molitor hearts perfused in situ, in which inotropic activity was assessed by the systolic variation of the cardiac luminal diameter. Increasing the pacing rate from 1.0 to 2.5 Hz depressed contraction amplitude and accelerated relaxation. To avoid inotropic interference of variations in spontaneous rate, which have been shown to occur in insect heart during maneuvers that affect Ca2+ cycling, experiments were performed under electrical pacing at near-physiological rates. Raising the extracellular Ca2+ concentration from 0.5 to 8 mM increased contraction amplitude in a manner sensitive to L-type Ca2+ channel blockade by D600. Inotropic depression was observed after treatment with caffeine or thapsigargin, which impair Ca2+ accumulation by the sarcoplasmic reticulum (SR). D600, but not inhibition of the sarcolemmal Na+/Ca2+ exchanger by KB-R7943, further depressed inotropic activity in thapsigargin-treated hearts. From these results, it is possible to conclude that in T. molitor heart, as in vertebrates: (a) inotropic and lusitropic activities are modulated by the heart rate; and (b) Ca2+ availability for contraction depends on both Ca2+ influx via L-type channels and Ca2+ release from the SR.
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Mattiazzi A, Bassani RA, Escobar AL, Palomeque J, Valverde CA, Vila Petroff M, Bers DM. Chasing cardiac physiology and pathology down the CaMKII cascade. Am J Physiol Heart Circ Physiol 2015; 308:H1177-91. [PMID: 25747749 DOI: 10.1152/ajpheart.00007.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 02/16/2015] [Indexed: 11/22/2022]
Abstract
Calcium dynamics is central in cardiac physiology, as the key event leading to the excitation-contraction coupling (ECC) and relaxation processes. The primary function of Ca(2+) in the heart is the control of mechanical activity developed by the myofibril contractile apparatus. This key role of Ca(2+) signaling explains the subtle and critical control of important events of ECC and relaxation, such as Ca(2+) influx and SR Ca(2+) release and uptake. The multifunctional Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) is a signaling molecule that regulates a diverse array of proteins involved not only in ECC and relaxation but also in cell death, transcriptional activation of hypertrophy, inflammation, and arrhythmias. CaMKII activity is triggered by an increase in intracellular Ca(2+) levels. This activity can be sustained, creating molecular memory after the decline in Ca(2+) concentration, by autophosphorylation of the enzyme, as well as by oxidation, glycosylation, and nitrosylation at different sites of the regulatory domain of the kinase. CaMKII activity is enhanced in several cardiac diseases, altering the signaling pathways by which CaMKII regulates the different fundamental proteins involved in functional and transcriptional cardiac processes. Dysregulation of these pathways constitutes a central mechanism of various cardiac disease phenomena, like apoptosis and necrosis during ischemia/reperfusion injury, digitalis exposure, post-acidosis and heart failure arrhythmias, or cardiac hypertrophy. Here we summarize significant aspects of the molecular physiology of CaMKII and provide a conceptual framework for understanding the role of the CaMKII cascade on Ca(2+) regulation and dysregulation in cardiac health and disease.
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Affiliation(s)
- Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, The National Scientific and Technical Research Council-La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina;
| | - Rosana A Bassani
- Centro de Engenharia Biomédica, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | - Ariel L Escobar
- Biological Engineering and Small Scale Technologies, School of Engineering, University of California, Merced, California; and
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, The National Scientific and Technical Research Council-La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares, The National Scientific and Technical Research Council-La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Martín Vila Petroff
- Centro de Investigaciones Cardiovasculares, The National Scientific and Technical Research Council-La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Donald M Bers
- Department of Pharmacology, University of California Davis, Davis, California
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Louch WE, Koivumäki JT, Tavi P. Calcium signalling in developing cardiomyocytes: implications for model systems and disease. J Physiol 2015; 593:1047-63. [PMID: 25641733 PMCID: PMC4358669 DOI: 10.1113/jphysiol.2014.274712] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 12/28/2014] [Indexed: 12/15/2022] Open
Abstract
Adult cardiomyocytes exhibit complex Ca(2+) homeostasis, enabling tight control of contraction and relaxation. This intricate regulatory system develops gradually, with progressive maturation of specialized structures and increasing capacity of Ca(2+) sources and sinks. In this review, we outline current understanding of these developmental processes, and draw parallels to pathophysiological conditions where cardiomyocytes exhibit a striking regression to an immature state of Ca(2+) homeostasis. We further highlight the importance of understanding developmental physiology when employing immature cardiomyocyte models such as cultured neonatal cells and stem cells.
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Affiliation(s)
- William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo0424, Oslo, Norway
- K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo0316, Oslo, Norway
| | - Jussi T Koivumäki
- Simula Research Laboratory, Center for Cardiological Innovation and Center for Biomedical ComputingOslo, Norway
| | - Pasi Tavi
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern FinlandKuopio, Finland
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Zhang C, Shan XL, Liao YL, Zhao P, Guo W, Wei HC, Lu R. Effects of stachydrine on norepinephrine-induced neonatal rat cardiac myocytes hypertrophy and intracellular calcium transients. Altern Ther Health Med 2014; 14:474. [PMID: 25488774 PMCID: PMC4295334 DOI: 10.1186/1472-6882-14-474] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 11/27/2014] [Indexed: 01/12/2023]
Abstract
Background Leonurus heterophyllus sweet has been suggested to have cardioprotective effects against heart diseases, including ischemic diseases and ventricular remodeling. However, the active ingredients of the herb and the underlying mechanisms are poorly understood. The aim of the present study was to investigate the effects of stachydrine (STA), a major constituent of Leonurus heterophyllus sweet, on norepinephrine (NE) induced hypertrophy and the changes of calcium transients in neonatal rat cardiomyocytes. Methods Ventricular myocytes from 1-day-old Wistar rats were isolated and cultured in DMEM/F12 with 1 μmol/L norepinephrine in the presence or absence of 10 μmol/L STA for 72 h. Cardiomyocytes hypertrophy was evaluated by cell surface area, total protein/DNA content, β/α-MHC mRNA ratio. While calcium handling function was evaluated by Ca2+-transient amplitude and decay, SERCA2a activity and expression, PLN expression and phosphorylation. β1-adrenergic receptor system activation was evaluated by the content of cAMP and the activation of PKA. Results NE treatment increases the cell surface area, protein synthesis, the expression level of β-MHC and β/α-MHC ratio. These effects were attenuated by STA. NE-induced hypertrophy was associated with increased Ca2+-transient amplitude, accelerated decay of the Ca2+-transient, increased phospholamban expression, hyper-phosphorylation at both the serine-16 and threonine-17 residues, increased intracellular cAMP level, and PKA overactivation. All of which were significantly inhibited by STA. Conclusion These data suggest that STA attenuates norepinephrine-induced cardiomyocyte hypertrophy and has potential protective effects against β-adrenergic receptor induced Ca2+ mishandling.
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Puglisi JL, Goldspink PH, Gomes AV, Utter MS, Bers DM, Solaro RJ. Influence of a constitutive increase in myofilament Ca(2+)-sensitivity on Ca(2+)-fluxes and contraction of mouse heart ventricular myocytes. Arch Biochem Biophys 2014; 552-553:50-9. [PMID: 24480308 PMCID: PMC4043955 DOI: 10.1016/j.abb.2014.01.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 01/02/2014] [Accepted: 01/18/2014] [Indexed: 11/25/2022]
Abstract
Chronic increases in myofilament Ca(2+)-sensitivity in the heart are known to alter gene expression potentially modifying Ca(2+)-homeostasis and inducing arrhythmias. We tested age-dependent effects of a chronic increase in myofilament Ca(2+)-sensitivity on induction of altered alter gene expression and activity of Ca(2+) transport systems in cardiac myocytes. Our approach was to determine the relative contributions of the major mechanisms responsible for restoring Ca(2+) to basal levels in field stimulated ventricular myocytes. Comparisons were made from ventricular myocytes isolated from non-transgenic (NTG) controls and transgenic mice expressing the fetal, slow skeletal troponin I (TG-ssTnI) in place of cardiac TnI (cTnI). Replacement of cTnI by ssTnI induces an increase in myofilament Ca(2+)-sensitivity. Comparisons included myocytes from relatively young (5-7months) and older mice (11-13months). Employing application of caffeine in normal Tyrode and in 0Na(+) 0Ca(2+) solution, we were able to dissect the contribution of the sarcoplasmic reticulum Ca(2+) pump (SR Ca(2+)-ATPase), the Na(+)/Ca(2+) exchanger (NCX), and "slow mechanisms" representing the activity of the sarcolemmal Ca(2+) pump and the mitochondrial Ca(2+) uniporter. The relative contribution of the SR Ca(2+)-ATPase to restoration of basal Ca(2+) levels in younger TG-ssTnI myocytes was lower than in NTG (81.12±2.8% vs 92.70±1.02%), but the same in the older myocytes. Younger and older NTG myocytes demonstrated similar contributions from the SR Ca(2+)-ATPase and NCX to restoration of basal Ca(2+). However, the slow mechanisms for Ca(2+) removal were increased in the older NTG (3.4±0.3%) vs the younger NTG myocytes (1.4±0.1%). Compared to NTG, younger TG-ssTnI myocytes demonstrated a significantly bigger contribution of the NCX (16±2.7% in TG vs 6.9±0.9% in NTG) and slow mechanisms (3.3±0.4% in TG vs 1.4±0.1% in NTG). In older TG-ssTnI myocytes the contributions were not significantly different from NTG (NCX: 4.9±0.6% in TG vs 5.5±0.7% in NTG; slow mechanisms: 2.5±0.3% in TG vs 3.4±0.3% in NTG). Our data indicate that constitutive increases in myofilament Ca(2+)-sensitivity alter the relative significance of the NCX transport system involved in Ca(2+)-homeostasis only in a younger group of mice. This modification may be of significance in early changes in altered gene expression and electrical stability hearts with increased myofilament Ca-sensitivity.
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Affiliation(s)
- Jose L Puglisi
- Department of Pharmacology, University of California Davis, Davis, CA 95616, United States
| | - Paul H Goldspink
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Aldrin V Gomes
- Department of Neurobiology, Physiology, and Behavior, University of California Davis, Davis, CA 95616, United States
| | - Megan S Utter
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Donald M Bers
- Department of Pharmacology, University of California Davis, Davis, CA 95616, United States
| | - R John Solaro
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, United States.
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Bassani RA, Gilioli R, Oliveira ES, Hoehr NF. Blood Calcium Levels in Immature Rats: Influence of Extracellular Calcium Concentration on Myocardial Calcium Handling. Exp Anim 2012; 61:399-405. [DOI: 10.1538/expanim.61.399] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Affiliation(s)
| | - Rovilson Gilioli
- Multidisciplinary Center for Biological Investigation on Laboratory Animals Science, University of Campinas
| | | | - Nelci F. Hoehr
- Department of Clinical Pathology, School of Medical Sciences. University of Campinas
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Ziman AP, Gómez-Viquez NL, Bloch RJ, Lederer WJ. Excitation-contraction coupling changes during postnatal cardiac development. J Mol Cell Cardiol 2010; 48:379-86. [PMID: 19818794 PMCID: PMC3097073 DOI: 10.1016/j.yjmcc.2009.09.016] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 09/14/2009] [Accepted: 09/26/2009] [Indexed: 01/09/2023]
Abstract
Cardiac contraction is initiated by the release of Ca(2+) from intracellular stores in response to an action potential, in a process known as "excitation-contraction coupling" (ECC). Here we investigate the maturation of ECC in the rat heart during postnatal development. We provide new information on how proteins of the sarcoplasmic reticulum (SR) and the t-tubules (TTs) assemble to form the structures that support EC coupling during postnatal development. We show that the surface membrane protein, caveolin-3 (Cav3), is a good protein marker for TTs in ventricular myocytes and compared it quantitatively to junctophilin-2 (JP2), a protein found on the SR at sites of SR-TT junctions, or couplons. Although JP2 and Cav3 associate primarily with the SR and TTs, respectively, we found that they occupy the appropriate sites at maturing structures in synchrony, as visualized with high resolution, quantitative 3-dimensional imaging. We also found the surprising result that while both ryanodine receptor type 2, (RyR2) and JP2 proteins are localized to the same membrane and sub-compartments, they assume their positions at very different rates: RyR2 moves to the SR membrane at the Z-disc very early in development while JP2 only appears in the SR membrane as the TTs mature. Our data suggest that, although RyR2 appears to be prepositioned at the sites ultimately occupied by dyad junctions, JP2 arrives at these sites in synchrony with the development of the TTs at the Z-discs. Finally, we report that EC coupling efficiency changes with development, in concert with these structural changes. Thus we provide the first well-integrated information that links the developing organization of proteins underlying EC coupling (RyR2, DHPR, Cav3 and JP2) to the developing efficacy of EC coupling.
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Affiliation(s)
- Andrew P Ziman
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, 725 West Lombard St Baltimore, MD 21201, USA
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Guo A, Yang HT. Ca2+removal mechanisms in mouse embryonic stem cell-derived cardiomyocytes. Am J Physiol Cell Physiol 2009; 297:C732-41. [DOI: 10.1152/ajpcell.00025.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In mammalian adult cardiomyocytes, sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA) plays a major role in controlling the decline of cytosolic free Ca2+concentration ([Ca2+]i) in comparison with sarcolemmal Na+/Ca2+exchanger (NCX). However, the functional importance of SERCA and NCX in cytosolic Ca2+removal during early cardiomyogenesis is still debated. In this study, the functional contributions of Ca2+transporters to [Ca2+]idecline in mouse embryonic stem cell-derived cardiomyocytes (mESCMs), a suitable model for investigation of early cardiogenesis, at various differentiation stages were investigated. We estimated that even at early differentiation stages of mESCMs, SERCA was responsible for ∼76% of total Ca2+removal, while NCX was responsible for ∼21%. The contributions of SERCA and NCX to cytosolic Ca2+clearance were increased to ∼88% and decreased to ∼10%, respectively, at the late differentiation stage. Dynamical analysis of the transient decay phases in normal and Na+-free solutions suggests that the contribution of NCX to [Ca2+]idecline is more apparent in the terminal slow decay phase than that in the initial fast phase. When SR function was suppressed in type 2 ryanodine receptor-null mESCMs or with ryanodine receptor and SERCA inhibitors (ryanodine and thapsigargin), NCX acted as the main pathway for [Ca2+]idecline. We conclude that the rapid [Ca2+]idecline is mainly achieved by the SR uptake even at the early differentiation stage of mESCMs, while NCX acts as the main Ca2+remover when SR function is suppressed. These findings suggest a critical role of SR in the regulation of [Ca2+]ihomeostasis even in differentiating cardiomyocytes.
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Affiliation(s)
- Ang Guo
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and Shanghai Jiao Tong University School of Medicine
| | - Huang-Tian Yang
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and Shanghai Jiao Tong University School of Medicine
- Shanghai Stem Cell Institute, Shanghai Jiao Tong University School of Medicine; and
- Shanghai Key Laboratory of Vascular Biology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Costa AR, Torres LB, Medei E, Ricardo RA, França JP, Smaili S, Nascimento JHM, Oshiro MEM, Bassani JWM, Ferreira AT, Tucci PJF. The negative inotropic action of canrenone is mediated by L-type calcium current blockade and reduced intracellular calcium transients. Br J Pharmacol 2009; 158:580-7. [PMID: 19663883 DOI: 10.1111/j.1476-5381.2009.00329.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND AND PURPOSE Adding spironolactone to standard therapy in heart failure reduces morbidity and mortality, but the underlying mechanisms are not fully understood. We analysed the effect of canrenone, the major active metabolite of spironolactone, on myocardial contractility and intracellular calcium homeostasis. EXPERIMENTAL APPROACH Left ventricular papillary muscles and cardiomyocytes were isolated from male Wistar rats. Contractility of papillary muscles was assessed with force transducers, Ca(2+) transients by fluorescence and Ca(2+) fluxes by electrophysiological techniques. KEY RESULTS Canrenone (300-600 micromol L(-1)) reduced developed tension, maximum rate of tension increase and maximum rate of tension decay of papillary muscles. In cardiomyocytes, canrenone (50 micromol L(-1)) reduced cell shortening and L-type Ca(2+) channel current, whereas steady-state activation and inactivation, and reactivation curves were unchanged. Canrenone also decreased the Ca(2+) content of the sarcoplasmic reticulum, intracellular Ca(2+) transient amplitude and intracellular diastolic Ca(2+) concentration. However, the time course of [Ca(2+)](i) decline during transients evoked by caffeine was not affected by canrenone. CONCLUSION AND IMPLICATIONS Canrenone reduced L-type Ca(2+) channel current, amplitude of intracellular Ca(2+) transients and Ca(2+) content of sarcoplasmic reticulum in cardiomyocytes. These changes are likely to underlie the negative inotropic effect of canrenone.
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Affiliation(s)
- A R Costa
- Cardiology Division, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil.
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de Oliveira PX, Bassani RA, Bassani JWM. Lethal effect of electric fields on isolated ventricular myocytes. IEEE Trans Biomed Eng 2009; 55:2635-42. [PMID: 18990634 DOI: 10.1109/tbme.2008.2001135] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Defibrillator-type shocks may cause electric and contractile dysfunction. In this study, we determined the relationship between probability of lethal injury and electric field intensity (E in isolated rat ventricular myocytes, with emphasis on field orientation and stimulus waveform. This relationship was sigmoidal with irreversible injury for E > 50 V/cm . During both threshold and lethal stimulation, cells were twofold more sensitive to the field when it was applied longitudinally (versus transversally) to the cell major axis. For a given E, the estimated maximum variation of transmembrane potential (Delta V(max)) was greater for longitudinal stimuli, which might account for the greater sensitivity to the field. Cell death, however, occurred at lower maximum Delta V(max) values for transversal shocks. This might be explained by a less steep spatial decay of transmembrane potential predicted for transversal stimulation, which would possibly result in occurrence of electroporation in a larger membrane area. For the same stimulus duration, cells were less sensitive to field-induced injury when shocks were biphasic (versus monophasic). Ours results indicate that, although significant myocyte death may occur in the E range expected during clinical defibrillation, biphasic shocks are less likely to produce irreversible cell injury.
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Affiliation(s)
- Pedro Xavier de Oliveira
- Departamento de Engenharia Biomédica, Faculdade de Engenharia Elétrica e de Computacão (FEEC), Universidade Estadual de Campinas, 13084-971 Campinas, São Paulo, Brazil.
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Wang LJ, Sobie EA. Mathematical model of the neonatal mouse ventricular action potential. Am J Physiol Heart Circ Physiol 2008; 294:H2565-75. [PMID: 18408122 DOI: 10.1152/ajpheart.01376.2007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Therapies for heart disease are based largely on our understanding of the adult myocardium. The dramatic differences in action potential (AP) shape between neonatal and adult cardiac myocytes, however, indicate that a different set of molecular interactions in neonatal myocytes necessitates different treatment for newborns. Computational modeling is useful for synthesizing data to determine how interactions between components lead to systems-level behavior, but this technique has not been used extensively to study neonatal heart cell function. We created a mathematical model of the neonatal (day 1) mouse myocyte by modifying, on the basis of experimental data, the densities and/or formulations of ion transport mechanisms in an adult cell model. The new model reproduces the characteristic AP shape of neonatal cells, with a brief plateau phase and longer duration than the adult (action potential duration at 80% repolarization = 60.1 vs. 12.6 ms). The simulation results are consistent with experimental data, including 1) decreased density and altered inactivation of transient outward K+ currents, 2) increased delayed rectifier K+ currents, 3) Ca2+ entry through T-type as well as L-type Ca2+ channels, 4) increased Ca2+ influx through Na+/Ca2+ exchange, and 5) Ca2+ transients resulting from transmembrane Ca2+ entry rather than release from the sarcoplasmic reticulum (SR). Simulations performed with the model generated novel predictions, including increased SR Ca2+ leak and elevated intracellular Na+ concentration in neonatal compared with adult myocytes. This new model can therefore be used for testing hypotheses and obtaining a better quantitative understanding of differences between neonatal and adult physiology.
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Affiliation(s)
- Linda J Wang
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York, USA
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Huang J, Hove-Madsen L, Tibbits GF. SR Ca2+refilling upon depletion and SR Ca2+uptake rates during development in rabbit ventricular myocytes. Am J Physiol Cell Physiol 2007; 293:C1906-15. [DOI: 10.1152/ajpcell.00241.2007] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
While it has been reported that a sparse sarcoplasmic reticulum (SR) and a low SR Ca2+pump density exist at birth, we and others have recently shown that significant amounts of Ca2+are stored in the neonatal rabbit heart SR. Here we try to determine developmental changes in SR Ca2+loading mechanisms and Ca2+pump efficacy in rabbit ventricular myocytes. SR Ca2+loading (loadSR) and k0.5(Ca2+concentration at half-maximal SR Ca2+uptake) were higher and lower, respectively, in younger age groups. Inhibition of the L-type calcium current ( ICa) with 15 μM nifedipine dramatically reduced loadSRin older but not in younger age groups. In contrast, subsequent inhibition of the Na+/Ca2+exchanger (NCX) with 10 μM KB-R7943 strongly reduced loadSRin the younger but not the older age groups. Accordingly, the time integral of the inward NCX current (tail INCX) elicited on repolarization was highly sensitive to nifedipine in the older groups and sensitive to KB-R7943 in the younger groups. Interestingly, slow SR loading took place in the presence of both nifedipine and KB-R7943 in all age groups, although it was less prominent in the older groups. We conclude that the SR loading capacity at the earliest postnatal stages is at least as large as that of adult myocytes. However, reverse-mode NCX plays a prominent role in SR Ca2+loading at early postnatal stages while ICais the main source of SR Ca2+loading at late postnatal and adult stages.
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Carvalho BMR, Bassani RA, Franchini KG, Bassani JWM. Enhanced calcium mobilization in rat ventricular myocytes during the onset of pressure overload-induced hypertrophy. Am J Physiol Heart Circ Physiol 2006; 291:H1803-13. [PMID: 16648178 DOI: 10.1152/ajpheart.01345.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Early cardiovascular changes evoked by pressure overload (PO) may reveal adaptive strategies that allow immediate survival to the increased hemodynamic load. In this study, systolic and diastolic Ca2+ cycling was analyzed in left ventricular rat myocytes before ( day 2, PO-2d group) and after ( day 7, PO-7d group) development of hypertrophy subsequent to aortic constriction, as well as in myocytes from time-matched sham-operated rats (sham group). Ca2+ transient amplitude was significantly augmented in the PO-2d group. In the PO-7d group, intracellular Ca2+ concentration ([Ca2+]i) was reduced during diastole, and mechanical twitch relaxation (but not [Ca2+]i decline) was slowed. In PO groups, fractional sarcoplasmic reticulum (SR) Ca2+ release at a twitch, SR Ca2+ content, SR Ca2+ loss during diastole, and SR-dependent integrated Ca2+ flux during twitch relaxation were significantly greater than in sham-operated groups, whereas the relaxation-associated Ca2+ flux carried by the Na+/Ca2+ exchanger was not significantly changed. In the PO-7d group, mRNA levels of cardiac isoforms of SR Ca2+-ATPase (SERCA2a), phospholamban, calsequestrin, ryanodine receptor, and NCX were not significantly altered, but the SERCA2a-to-phospholamban ratio was increased 2.5-fold. Moreover, greater sensitivity to the inotropic effects of the β-adrenoceptor agonist isoproterenol was observed in the PO-7d group. The results indicate enhanced Ca2+ cycling between SR and cytosol early after PO imposition, even before hypertrophy development. Increase in SR Ca2+ uptake may contribute to enhancement of excitation-contraction coupling (augmented SR Ca2+ content and release) and protection against arrhythmogenesis due to buildup of [Ca2+]i during diastole.
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Affiliation(s)
- Beatriz M R Carvalho
- Centro de Engenharia Biomédica, Universidade Estadual de Campinas, Caixa Postal 6040, 13084-971 Campinas, SP, Brazil
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Lorenzen-Schmidt I, Stuyvers BD, ter Keurs HE, Date MO, Hoshijima M, Chien KR, McCulloch AD, Omens JH. Young MLP deficient mice show diastolic dysfunction before the onset of dilated cardiomyopathy. J Mol Cell Cardiol 2006; 39:241-50. [PMID: 15978612 PMCID: PMC4484861 DOI: 10.1016/j.yjmcc.2005.05.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 04/29/2005] [Accepted: 05/11/2005] [Indexed: 11/30/2022]
Abstract
Targeted deletion of cytoskeletal muscle LIM protein (MLP) in mice consistently leads to dilated cardiomyopathy (DCM) after one or more months. However, next to nothing is known at present about the mechanisms of this process. We investigated whether diastolic performance including passive mechanics and systolic behavior are altered in 2-week-old MLP knockout (MLPKO) mice, in which heart size, fractional shortening and ejection fraction are still normal. Right ventricular trabeculae were isolated from 2-week-old MLPKO and wildtype mice and placed in an apparatus that allowed force measurements and sarcomere length measurements using laser diffraction. During a twitch from the unloaded state at 1 Hz, MLPKO muscles relengthened to slack length more slowly than controls, although the corresponding force relaxation time was unchanged. Active developed stress at a diastolic sarcomere length of 2.00 microm was preserved in MLPKO trabeculae over a wide range of pacing frequencies. Force relaxation under the same conditions was consistently prolonged compared with wildtype controls, whereas time to peak and maximum rate of force generation were not significantly altered. Ca2+ content of the sarcoplasmic reticulum (SR) and the quantities of Ca2+ handling proteins were similar in both genotypes. In summary, young MLPKO mice revealed substantial alterations in passive myocardial properties and relaxation time, but not in most systolic characteristics. These results indicate that the progression to heart failure in the MLPKO model may be driven by diastolic myocardial dysfunction and abnormal passive properties rather than systolic dysfunction.
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Affiliation(s)
- Ilka Lorenzen-Schmidt
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA
| | - Bruno D. Stuyvers
- Department of Biophysics and Physiology, University of Calgary, Calgary, Alta., Canada T2N 1N4
| | - Henk E.D.J. ter Keurs
- Department of Biophysics and Physiology, University of Calgary, Calgary, Alta., Canada T2N 1N4
| | - Moto-o Date
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0613, USA
| | - Masahiko Hoshijima
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0613, USA
| | - Kenneth R. Chien
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0613, USA
| | - Andrew D. McCulloch
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA
| | - Jeffrey H. Omens
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0613, USA
- Corresponding author. Tel.: +1 858 534 8102; fax: +1 858 534 0522.
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Huang J, Hove-Madsen L, Tibbits GF. Na+/Ca2+ exchange activity in neonatal rabbit ventricular myocytes. Am J Physiol Cell Physiol 2004; 288:C195-203. [PMID: 15317663 DOI: 10.1152/ajpcell.00183.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Much less is known about the contributions of the Na(+)/Ca(2+) exchanger (NCX) and sarcoplasmic reticulum (SR) Ca(2+) pump to cell relaxation in neonatal compared with adult mammalian ventricular myocytes. Based on both biochemical and molecular studies, there is evidence of a much higher density of NCX at birth that subsequently decreases during the next 2 wk of development. It has been hypothesized, therefore, that NCX plays a relatively more important role for cytosolic Ca(2+) decline in neonates as well as, perhaps, a role in excitation-contraction coupling in reverse mode. We isolated neonatal ventricular myocytes from rabbits in four different age groups: 3, 6, 10, and 20 days of age. Using an amphotericin-perforated patch-clamp technique in fluo-3-loaded myocytes, we measured the caffeine-induced inward NCX current (I(NCX)) and the Ca(2+) transient. We found that the integral of I(NCX), an indicator of SR Ca(2+) content, was greatest in myocytes from younger age groups when normalized by cell surface area and that it decreased with age. The velocity of Ca(2+) extrusion by NCX (V(NCX)) was linear with [Ca(2+)] and did not indicate saturation kinetics until [Ca(2+)] reached 1-3 microM for each age group. There was a significantly greater time delay between the peaks of I(NCX) and the Ca(2+) transient in myocytes from the youngest age groups. This observation could be related to structural differences in the subsarcolemmal microdomains as a function of age.
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Affiliation(s)
- Jingbo Huang
- Cardiac Membrane Research Laboratory, Simon Fraser University, Burnaby, British Columbia, Canada
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Creazzo TL, Burch J, Godt RE. Calcium buffering and excitation-contraction coupling in developing avian myocardium. Biophys J 2004; 86:966-77. [PMID: 14747332 PMCID: PMC1303944 DOI: 10.1016/s0006-3495(04)74172-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2003] [Accepted: 09/23/2003] [Indexed: 12/20/2022] Open
Abstract
This report provides a detailed analysis of developmental changes in cytoplasmic free calcium (Ca(2+)) buffering and excitation-contraction coupling in embryonic chick ventricular myocytes. The peak magnitude of field-stimulated Ca(2+) transients declined by 41% between embryonic day (ED) 5 and 15, with most of the decline occurring between ED5 and 11. This was due primarily to a decrease in Ca(2+) currents. Sarcoplasmic reticulum (SR) Ca(2+) content increased 14-fold from ED5 to 15. Ca(2+) transients in voltage-clamped myocytes after blockade of SR function permitted computation of the fast Ca buffer power of the cytosol as expressed as generalized values of B(max) and K(D). B(max) rose with development whereas K(D) did not change significantly. The computed SR Ca(2+) contribution to the Ca(2+) transient and gain factor for Ca(2+)-induced Ca(2+) release increased markedly between ED5 and 11 and slightly thereafter. These results paralleled the maturation of SR and peripheral couplings reported by others and demonstrated a strong relationship between structure and function in development of excitation-contraction coupling. Modeling of buffer power from estimates of the major cytosolic Ca binding moieties yielded a B(max) and K(D) in reasonable agreement with experiment. From ED5 to 15, troponin C was the major Ca(2+) binding moiety, followed by SR and calmodulin.
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Affiliation(s)
- Tony L Creazzo
- Neonatal/Perinatal Research Institute, Department of Pediatrics/Neonatology Division, Duke University Medical Center, Durham, North Carolina 27710, USA.
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