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Petkova MA, Dobrzynski H. Do human sinoatrial node cells have t-tubules? TRANSLATIONAL RESEARCH IN ANATOMY 2021. [DOI: 10.1016/j.tria.2021.100131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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2
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Kaur K, Jalife J. Is TGF-β 1 (Transforming Growth Factor-β 1) an Enabler of Myofibroblast-Cardiomyocyte Cross Talk? Circ Arrhythm Electrophysiol 2019; 10:e005289. [PMID: 28500179 DOI: 10.1161/circep.117.005289] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Kuljeet Kaur
- From the Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor (K.K., J.J.); Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain (J.J.); and Centro de Investigación Biomédica en Red, Enfermedades Cardiovasculares, Spain (J.J.)
| | - José Jalife
- From the Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor (K.K., J.J.); Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain (J.J.); and Centro de Investigación Biomédica en Red, Enfermedades Cardiovasculares, Spain (J.J.).
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Frisk M, Koivumäki JT, Norseng PA, Maleckar MM, Sejersted OM, Louch WE. Variable t-tubule organization and Ca2+ homeostasis across the atria. Am J Physiol Heart Circ Physiol 2014; 307:H609-20. [PMID: 24951751 DOI: 10.1152/ajpheart.00295.2014] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Although t-tubules have traditionally been thought to be absent in atrial cardiomyocytes, recent studies have suggested that t-tubules exist in the atria of large mammals. However, it is unclear whether regional differences in t-tubule organization exist that define cardiomyocyte function across the atria. We sought to investigate regional t-tubule density in pig and rat atria and the consequences for cardiomyocyte Ca(2+) homeostasis. We observed t-tubules in approximately one-third of rat atrial cardiomyocytes, in both tissue cryosections and isolated cardiomyocytes. In a minority (≈10%) of atrial cardiomyocytes, the t-tubular network was well organized, with a transverse structure resembling that of ventricular cardiomyocytes. In both rat and pig atrial tissue, we observed higher t-tubule density in the epicardium than in the endocardium. Consistent with high variability in the distribution of t-tubules and Ca(2+) channels among cells, L-type Ca(2+) current amplitude was also highly variable and steeply dependent on capacitance and t-tubule density. Accordingly, Ca(2+) transients showed great variability in Ca(2+) release synchrony. Simultaneous imaging of the cell membrane and Ca(2+) transients confirmed t-tubule functionality. Results from mathematical modeling indicated that a transmural gradient in t-tubule organization and Ca(2+) release kinetics supports synchronization of contraction across the atrial wall and may underlie transmural differences in the refractory period. In conclusion, our results indicate that t-tubule density is highly variable across the atria. We propose that higher t-tubule density in cells localized in the epicardium may promote synchronization of contraction across the atrial wall.
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Affiliation(s)
- Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway;
| | - Jussi T Koivumäki
- Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway; and Center for Cardiological Innovation, Oslo University Hospital, Oslo, Norway
| | - Per A Norseng
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Mary M Maleckar
- Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway; and Center for Cardiological Innovation, Oslo University Hospital, Oslo, Norway
| | - Ole M Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
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Graciotti L, Becker J, Granata AL, Procopio AD, Tessarollo L, Fulgenzi G. Dystrophin is required for the normal function of the cardio-protective K(ATP) channel in cardiomyocytes. PLoS One 2011; 6:e27034. [PMID: 22066028 PMCID: PMC3205025 DOI: 10.1371/journal.pone.0027034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 10/09/2011] [Indexed: 12/19/2022] Open
Abstract
Duchenne and Becker muscular dystrophy patients often develop a cardiomyopathy for which the pathogenesis is still unknown. We have employed the murine animal model of Duchenne muscular dystrophy (mdx), which develops a cardiomyopathy that includes some characteristics of the human disease, to study the molecular basis of this pathology. Here we show that the mdx mouse heart has defects consistent with alteration in compounds that regulate energy homeostasis including a marked decrease in creatine-phosphate (PC). In addition, the mdx heart is more susceptible to anoxia than controls. Since the cardio-protective ATP sensitive potassium channel (KATP) complex and PC have been shown to interact we investigated whether deficits in PC levels correlate with other molecular events including KATP ion channel complex presence, its functionality and interaction with dystrophin. We found that this channel complex is present in the dystrophic cardiac cell membrane but its ability to sense a drop in the intracellular ATP concentration and consequently open is compromised by the absence of dystrophin. We further demonstrate that the creatine kinase muscle isoform (CKm) is displaced from the plasma membrane of the mdx cardiac cells. Considering that CKm is a determinant of KATP channel complex function we hypothesize that dystrophin acts as a scaffolding protein organizing the KATP channel complex and the enzymes necessary for its correct functioning. Therefore, the lack of proper functioning of the cardio-protective KATP system in the mdx cardiomyocytes may be part of the mechanism contributing to development of cardiac disease in dystrophic patients.
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Affiliation(s)
- Laura Graciotti
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
| | - Jodi Becker
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Anna Luisa Granata
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
| | - Antonio Domenico Procopio
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
- Center of Clinical Pathology and Innovative Therapy, INRCA, Ancona, Italy
| | - Lino Tessarollo
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- * E-mail: (GF); (LT)
| | - Gianluca Fulgenzi
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- * E-mail: (GF); (LT)
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Colussi C, Berni R, Rosati J, Straino S, Vitale S, Spallotta F, Baruffi S, Bocchi L, Delucchi F, Rossi S, Savi M, Rotili D, Quaini F, Macchi E, Stilli D, Musso E, Mai A, Gaetano C, Capogrossi MC. The histone deacetylase inhibitor suberoylanilide hydroxamic acid reduces cardiac arrhythmias in dystrophic mice. Cardiovasc Res 2010; 87:73-82. [DOI: 10.1093/cvr/cvq035] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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7
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Kakarla SK, Rice KM, Katta A, Paturi S, Wu M, Kolli M, Keshavarzian S, Manzoor K, Wehner PS, Blough ER. Possible molecular mechanisms underlying age-related cardiomyocyte apoptosis in the F344XBN rat heart. J Gerontol A Biol Sci Med Sci 2010; 65:147-55. [PMID: 20056683 DOI: 10.1093/gerona/glp203] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Despite advances in treatment, age-related cardiac dysfunction still remains a leading cause of cardiovascular death. Recent data have suggested that increases in cardiomyocyte apoptosis may be involved in the pathological remodeling of heart. Here, we examine the effects of aging on cardiomyocyte apoptosis in 6-, 30-, and 36-month-old Fischer344 x Brown Norway F1 hybrid rats (F344XBN). Compared with 6-month hearts, aged hearts exhibited increased TdT-mediated dUTP nick end labeling-positive nuclei, caspase-3 activation, caspase-dependent cleavage of alpha-fodrin and diminished phosphorylation of protein kinase B/Akt (Thr 308). These age-dependent increases in cardiomyocyte apoptosis were associated with alterations in the composition of the cardiac dystrophin glycoprotein complex and elevated cytoplasmic IgG and albumin immunoreactivity. Immunohistochemical analysis confirmed these data and demonstrated qualitative differences in localization of dystrophin-glycoprotein complex (DGC) molecules with aging. Taken together, these data suggest that aging-related increases in cardiac apoptotic activity model may be due, at least in part, to age-associated changes in DGC structure.
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Affiliation(s)
- Sunil K Kakarla
- Laboratory of Molecular Physiology, Robert C. Byrd Biotechnology Science Center, Department of Biological Sciences, 1700 3rd Avenue, Marshall University, Huntington, WV 25755-1090, USA
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L-type Ca2+ channel function is linked to dystrophin expression in mammalian muscle. PLoS One 2008; 3:e1762. [PMID: 18516256 PMCID: PMC2408559 DOI: 10.1371/journal.pone.0001762] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 02/08/2008] [Indexed: 11/19/2022] Open
Abstract
Background In dystrophic mdx skeletal muscle, aberrant Ca2+ homeostasis and fibre degeneration are found. The absence of dystrophin in models of Duchenne muscular dystrophy (DMD) has been connected to altered ion channel properties e.g. impaired L-type Ca2+ currents. In regenerating mdx muscle, ‘revertant’ fibres restore dystrophin expression. Their functionality involving DHPR-Ca2+-channels is elusive. Methods and Results We developed a novel ‘in-situ’ confocal immuno-fluorescence and imaging technique that allows, for the first time, quantitative subcellular dystrophin-DHPR colocalization in individual, non-fixed, muscle fibres. Tubular DHPR signals alternated with second harmonic generation signals originating from myosin. Dystrophin-DHPR colocalization was substantial in wt fibres, but diminished in most mdx fibres. Mini-dystrophin (MinD) expressing fibres successfully restored colocalization. Interestingly, in some aged mdx fibres, colocalization was similar to wt fibres. Most mdx fibres showed very weak membrane dystrophin staining and were classified ‘mdx-like’. Some mdx fibres, however, had strong ‘wt-like’ dystrophin signals and were identified as ‘revertants’. Split mdx fibres were mostly ‘mdx-like’ and are not generally ‘revertants’. Correlations between membrane dystrophin and DHPR colocalization suggest a restored putative link in ‘revertants’. Using the two-micro-electrode-voltage clamp technique, Ca2+-current amplitudes (imax) showed very similar behaviours: reduced amplitudes in most aged mdx fibres (as seen exclusively in young mdx mice) and a few mdx fibres, most likely ‘revertants’, with amplitudes similar to wt or MinD fibres. Ca2+ current activation curves were similar in ‘wt-like’ and ‘mdx-like’ aged mdx fibres and are not the cause for the differences in current amplitudes. imax amplitudes were fully restored in MinD fibres. Conclusions We present evidence for a direct/indirect DHPR-dystrophin interaction present in wt, MinD and ‘revertant’ mdx fibres but absent in remaining mdx fibres. Our imaging technique reliably detects single isolated ‘revertant’ fibres that could be used for subsequent physiological experiments to study mechanisms and therapy concepts in DMD.
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Shaw CA, Larochelle N, Dudley RWR, Lochmuller H, Danialou G, Petrof BJ, Karpati G, Holland PC, Nalbantoglu J. Simultaneous dystrophin and dysferlin deficiencies associated with high-level expression of the coxsackie and adenovirus receptor in transgenic mice. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 169:2148-60. [PMID: 17148677 PMCID: PMC1762479 DOI: 10.2353/ajpath.2006.060570] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The Coxsackie and adenovirus receptor (CAR), a cell adhesion molecule of the immunoglobulin superfamily, is usually confined to the sarcolemma at the neuromuscular junction in mature skeletal muscle fibers. Previously, we reported that adenovirus-mediated gene transfer is greatly facilitated in hemizygous transgenic mice with extrasynaptic CAR expression driven by a muscle-specific promoter. However, in the present study, when these mice were bred to homozygosity, they developed a severe myopathic phenotype and died prematurely. Large numbers of necrotic and regenerating fibers were present in the skeletal muscle of the homozygous CAR transgenics. The myopathy was further characterized by increased levels of caveolin-3 and beta-dystroglycan and decreased levels of dystrophin, dysferlin, and neuronal nitric-oxide synthase. Even the hemizygotes manifested a subtle phenotype, displaying deficits in isometric force generation and perturbed mitogen-activated protein kinase (MAPK-erk1/2) activation during contraction. There are few naturally occurring or engineered mouse lines showing as severe a skeletal myopathy as observed with ectopic expression of CAR in the homozygotes. Taken together, these findings suggest that substantial overexpression of CAR may lead to physiological dysfunction by disturbing sarcolemmal integrity (through dystrophin deficiency), impairing sarcolemmal repair (through dysferlin deficiency), and interfering with normal signaling (through alterations in caveolin-3 and neuronal nitric-oxide synthase levels).
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Affiliation(s)
- Christian A Shaw
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University Health Center and Meakins-Christie Laboratories, 3801 University St., Montreal, Quebec, Canada H3A 2B4
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Duan D. Challenges and opportunities in dystrophin-deficient cardiomyopathy gene therapy. Hum Mol Genet 2006; 15 Spec No 2:R253-61. [PMID: 16987891 PMCID: PMC2581718 DOI: 10.1093/hmg/ddl180] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The last decade has evidenced unprecedented progress in gene therapy of Duchenne and Becker muscular dystrophy (DMD and BMD) skeletal muscle disease. Cardiomyopathy is a leading cause of morbidity and mortality in both patients and carriers of DMD, BMD and X-linked dilated cardiomyopathy. However, there is little advance in heart gene therapy. The gene, the vector, vector delivery, the target tissue and animal models are five fundamental components in developing an effective gene therapy. Intensive effort has been made in optimizing gene transfer vectors and methods. Systemic and/or local delivery of recombinant adeno-associated viral vector have resulted in widespread transduction in the rodent heart. The current challenge is to define other parameters that are essential for a successful gene therapy such as the best candidate gene(s), the optimal expression level and the target tissue. This review focuses on these long-ignored aspects and points out future research directions. In particular, we need to address whether all or only some of the recently developed mini- and microgenes are protective in the heart, whether partial correction can lead to whole heart function improvement, whether over-expression is hazardous and whether correcting skeletal muscle disease can slow down or stop the progression of cardiomyopathy. Discussion is also made on whether the current mouse models can meet these research needs.
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Affiliation(s)
- Dongsheng Duan
- Department of Molecular Microbiology and Immunology, The University of Missouri School of Medicine, One Hospital Dr., Room M610G, MSB Columbia, MO 65212, USA.
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Brooks VL, Haywood JR, Johnson AK. Translation of salt retention to central activation of the sympathetic nervous system in hypertension. Clin Exp Pharmacol Physiol 2006; 32:426-32. [PMID: 15854153 DOI: 10.1111/j.1440-1681.2005.04206.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
1. Increased dietary salt increases blood pressure in many hypertensive individuals, producing salt-sensitive hypertension (SSH). The cause is unknown, but a major component appears to be activation of the sympathetic nervous system. The purpose of this short review is to present one hypothesis to explain how increased dietary salt increases sympathetic activity in SSH. 2. It is proposed that increased salt intake causes salt retention and raises plasma sodium chloride (NaCl) concentrations, which activate sodium/osmoreceptors to trigger sympathoexcitation. Moreover, we suggest that small and often undetectable increases in osmolality can drive significant sympathoexcitation, because the gain of the relationship between osmolality and increased sympathetic activity is enhanced. Multiple factors may contribute to this facilitation, including inappropriately elevated levels of angiotensin II or aldosterone, changes in gene expression or synaptic plasticity and increased sodium concentrations in cerebrospinal fluid. 3. Future studies are required to delineate the brain sites and mechanisms of action and interaction of osmolality and these amplification factors to elicit sustained sympathoexcitation in SSH.
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Affiliation(s)
- Virginia L Brooks
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon 97239, USA.
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Kaprielian RR, Severs NJ. Dystrophin and the cardiomyocyte membrane cytoskeleton in the healthy and failing heart. Heart Fail Rev 2005; 5:221-38. [PMID: 16228906 DOI: 10.1023/a:1009805419285] [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: 11/12/2022]
Abstract
The cardiomyocyte membrane cytoskeleton consists of the costameric proteins that mediate force transduction from the cell to the extracellular matrix, and a sub-membrane network composed of dystrophin and associated proteins. Studies of the precise cellular distribution of dystrophin and of the consequences of genetic mutations leading to abnormal expression of the dystrophin molecule, as occurs in Duchenne and Becker's muscular dystrophies, highlight potential functional roles of this sub-membrane protein complex in cardiomyocytes. Detailed investigation of dystrophin distribution using the complementary cell imaging techniques of immunoconfocal microscopy and freeze-fracture cytochemistry at the electron-microscopical level show that, in contrast to rat cardiomyocytes, the dystrophin network in human cardiomyocytes is locally enriched at costameres. Thus located, the dystrophin network appears to have a mechanical role, involving stabilization of the peripheral plasma membrane during the repetitive distortion associated with cardiac contraction and, in the human myocyte, contributing to lateral force-transduction. Evidence from animal models of muscular dystrophy and from investigation of the interactions of the sub-membrane cytoskeleton with other membrane-associated proteins including ion channels, receptors and enzymes, further suggests a role for dystrophin in organization and regulation of membrane domains. The relative preservation of the membrane cytoskeleton in non-dystrophic dilated cardiomyopathy and in ischemic cardiomyopathy, conditions in which the myocyte contractile apparatus and internal desmin-based cytoskeleton are commonly disrupted, emphasizes the vital role of the membrane cytoskeleton in cell survival. Continued cardiomyocyte survival despite loss of contractile protein organization has implications in the potential for reversibility of left ventricular remodeling that can be achieved in the clinical setting.
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Affiliation(s)
- R R Kaprielian
- National Heart and Lung Institute, Imperial College School of Medicine, London, UK
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Iwata Y, Shigekawa M, Wakabayashi S. Cardiac syntrophin isoforms: Species-dependent expression, association with dystrophin complex and subcellular localization. Mol Cell Biochem 2005; 268:59-66. [PMID: 15724438 DOI: 10.1007/s11010-005-2998-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Syntrophin is known to be a component of the dystrophin-glycoprotein complex (DGC), a membrane/cytoskeleton-anchoring structure that is essential for the maintenance of viability of sarcolemma. We purified DGC from hearts of human and several animal species, and compared their protein composition. While almost all components of DGC were present in various species, proteins with the apparent molecular mass of 50-65 kDa corresponding to syntrophin isoforms were very different among them. Three isoforms of syntrophin (alpha1, beta1, beta2) were expressed in hamster, rat and canine ventricles, whereas only alpha1-isoform was mainly expressed in human and rabbit ventricles. Immunohistochemical analysis revealed that alpha1-and beta2-syntrophins were co-localized in sarcolemma and in T-tubules of canine ventricles. However, despite membrane localization of most syntrophins, subcellular fractionation revealed that part of syntrophins were recovered in the cytosolic fraction devoid of other components of DGC, raising the possibility that syntrophins may play multiple roles in various intracellular sites of cardiac muscle cells. Species-dependent expression and unique subcellular localization of syntrophins in cardiac muscle may contribute to the variable severity of muscle dysgenesis caused by the same primary defect in components of DGC of human and other animal species.
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Affiliation(s)
- Yuko Iwata
- Department of Molecular Physiology, National Cardiovascular Center Research Institute, Fujishiro-dai, Suita, Osaka, Japan.
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Buranakarl C, Mathur S, Brown SA. Effects of dietary sodium chloride intake on renal function and blood pressure in cats with normal and reduced renal function. Am J Vet Res 2004; 65:620-7. [PMID: 15141883 DOI: 10.2460/ajvr.2004.65.620] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine effects of variations in dietary intake of sodium chloride (NaCl) on systemic arterial blood pressure (ABP) in cats with normal and reduced renal function. ANIMALS 21 adult cats (7 with intact kidneys [control cats; group C], 7 with unilateral renal infarction with contralateral nephrectomy [remnant-kidney model; group RK], and 7 with unilateral renal infarction and contralateral renal wrapping and concurrent oral administration of amlodipine [remnant-wrap model; group WA]). PROCEDURE All cats were sequentially fed 3 diets that differed only in NaCl content (50, 100, or 200 mg of Na/kg); each diet was fed for 7 days. The ABP was recorded continuously by radiotelemetry, and renal function (glomerular filtration rate [GFR]) was determined on the sixth day of each feeding period. RESULTS Dietary supplementation with NaCl did not affect ABP, but it increased GFR in groups C and WA. The renin-angiotensin-aldosterone axis was activated in groups RK and WA at the lowest NaCl intake, but supplementation with NaCl suppressed this activation in group WA. The lowest NaCl intake was associated with hypokalemia and a high fractional excretion of potassium that decreased in response to supplementation with NaCl. Arterial baroreceptor resetting was evident after chronic hypertension but was not modified by dietary supplementation with NaCl. CONCLUSIONS AND CLINICAL RELEVANCE Low NaCl intake was associated with inappropriate kaliuresis, reduced GFR, and activation of the renin-angiotensin-aldosterone axis without evidence of a beneficial effect on ABP. Therefore, this common dietary maneuver could contribute to hypokalemic nephropathy and progressive renal injury in cats.
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Affiliation(s)
- Chollada Buranakarl
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
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McMartin GA, Wirch E, Abraham N, Kargacin GJ. Postnatal changes in caldesmon expression and localization in cardiac myocytes. J Anat 2003; 203:369-77. [PMID: 14620377 PMCID: PMC1571179 DOI: 10.1046/j.1469-7580.2003.00228.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Caldesmon is a heat-stable protein found in both muscle and non-muscle tissue. It binds to a number of contractile and cytoskeletal proteins and may be involved in regulating acto-myosin interaction in smooth muscle cells and/or the assembly of microfilaments in muscle and non-muscle cells. We have shown previously that caldesmon is localized at the Z-lines in adult cardiac myocytes and that both the low- and high-molecular-weight forms (/-caldesmon and h-caldesmon, respectively) are present in atrial and ventricular myocytes. Here we examined the expression of caldesmon and its localization in freshly isolated cardiac myocytes during postnatal development and when these myocytes were grown in culture. We found that /-caldesmon is expressed in both neonatal and adult rat ventricular myocytes. The expression of h-caldesmon, however, was not detected in myocytes from newborn animals but increased during the first 2 weeks of postnatal development. Caldesmon was generally not co-localized with alpha-actinin at the Z-lines in neonatal myocytes but became increasingly more so during the first 2 weeks of postnatal development. When myocytes from 5- and 10-day-old rats were grown in primary culture, h-caldesmon expression decreased and caldesmon could not be detected at the Z-lines in the cultured cells. These results indicate that caldesmon plays a role at the Z-lines in adult cardiac myocytes; however, its localization at the Z-lines is not necessary for the prenatal development that occurs at these sites or for the establishment of a contractile phenotype in cultured cardiac myocytes.
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Affiliation(s)
- Gail A McMartin
- Department of Physiology and Biophysics, University of Calgary, Alberta, Canada
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Löhn M, Fürstenau M, Sagach V, Elger M, Schulze W, Luft FC, Haller H, Gollasch M. Ignition of calcium sparks in arterial and cardiac muscle through caveolae. Circ Res 2000; 87:1034-9. [PMID: 11090549 DOI: 10.1161/01.res.87.11.1034] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ca(2+) sparks are localized intracellular Ca(2+) events released through ryanodine receptors (RyRs) that control excitation-contraction coupling in heart and smooth muscle. Ca(2+) spark triggering depends on precise delivery of Ca(2+) ions through dihydropyridine (DHP)-sensitive Ca(2+) channels to RyRs of the sarcoplasmic reticulum (SR), a process requiring a very precise alignment of surface and SR membranes containing Ca(2+) influx channels and RyRs. Because caveolae contain DHP-sensitive Ca(2+) channels and may colocalize with SR, we tested the hypothesis that caveolae are the structural element necessary for the generation of Ca(2+) sparks. Using methyl-ss-cyclodextrin (dextrin) to deplete caveolae, we found that dextrin dose-dependently decreased the frequency, amplitude, and spatial size of Ca(2+) sparks in arterial smooth muscle cells and neonatal cardiomyocytes. However, temporal characteristics of Ca(2+) sparks were not significantly affected. We ruled out the possibility that the decreases in Ca(2+) spark frequency and size are caused by changes in DHP-sensitive L-type channels, SR Ca(2+) load, or changes in membrane potential. Our results suggest a novel signaling model that explains the formation of Ca(2+) sparks in a caveolae microdomain. The transient elevation in [Ca(2+)](i) at the inner mouth of a single caveolemmal Ca(2+) channel induces simultaneous activation and thus opens several RyRs to generate a local Ca(2+) release event, a Ca(2+) spark. Alterations in the molecular assembly and ultrastructure of caveolae may lead to pathophysiological changes in Ca(2+) signaling. Thus, caveolae may be intimately involved in cardiovascular cell dysfunction and disease.
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MESH Headings
- Aging/metabolism
- Animals
- Animals, Newborn
- Caffeine/pharmacology
- Calcium/metabolism
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Caveolae/metabolism
- Caveolae/ultrastructure
- Cell Membrane/metabolism
- Cell Membrane/ultrastructure
- Cell Separation
- Cells, Cultured
- Cholesterol/metabolism
- Cyclodextrins/pharmacology
- Dose-Response Relationship, Drug
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Myocardium/cytology
- Myocardium/metabolism
- Patch-Clamp Techniques
- Phosphodiesterase Inhibitors/pharmacology
- Rats
- Rats, Sprague-Dawley
- Ryanodine/pharmacology
- Sarcoplasmic Reticulum/metabolism
- beta-Cyclodextrins
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Affiliation(s)
- M Löhn
- Franz Volhard Clinic and Max Delbrück Center for Molecular Medicine, Charité University Hospitals, Humboldt University of Berlin, Germany
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Kaprielian RR, Stevenson S, Rothery SM, Cullen MJ, Severs NJ. Distinct patterns of dystrophin organization in myocyte sarcolemma and transverse tubules of normal and diseased human myocardium. Circulation 2000; 101:2586-94. [PMID: 10840009 DOI: 10.1161/01.cir.101.22.2586] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Genetic mutations of dystrophin and associated glycoproteins underlie cell degeneration in several inherited cardiomyopathies, although the precise physiological role of these proteins remains under discussion. We studied the distribution of dystrophin in relation to the force-transducing vinculin-rich costameres in left ventricular cardiomyocytes from normal and failing human hearts to further elucidate the function of this protein complex. METHODS AND RESULTS Single- and double-label immunoconfocal microscopy and parallel high-resolution immunogold fracture-label electron microscopy were used to localize dystrophin and vinculin in human left ventricular myocytes from normal (n=6) and failing hearts (idiopathic dilated cardiomyopathy, n=7, or ischemic heart disease, n=5). In control cardiomyocytes, dystrophin had a continuous distribution at the peripheral sarcolemma, with concentrated bands corresponding to the vinculin-rich costameres. Intracellular labeling extended along transverse (T) tubule membranes. Fracture-label confirmed this distribution, showing significantly greater label on plasma membrane fractures overlying I-bands (I-band 4.1+/-0.3 gold particles/micrometer A-band 3.3+/-0.2 gold particles/micrometer mean+/-SE, P=0.02). Hypertrophied myocytes from failing hearts showed maintenance of this surface distribution except in degenerating cells; there was a clear increase in intracellular dystrophin label reflecting T-tubule hypertrophy. CONCLUSIONS Dystrophin partially colocalizes with costameric vinculin in normal and hypertrophied myocytes, a distribution lost in degenerating cells. This suggests a primarily mechanical role for dystrophin in maintenance of cell membrane integrity in normal and hypertrophied myocytes. The presence of dystrophin in the cardiac T-tubule membrane, in contrast to its known absence in skeletal muscle T-tubules, implies additional roles for dystrophin in membrane domain organization.
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Affiliation(s)
- R R Kaprielian
- Cardiac Medicine, The National Heart and Lung Institute, Imperial College School of Medicine, London, England
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18
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Blatter LA. Cell volume measurements by fluorescence confocal microscopy: theoretical and practical aspects. Methods Enzymol 1999; 307:274-95. [PMID: 10506979 DOI: 10.1016/s0076-6879(99)07018-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Affiliation(s)
- L A Blatter
- Department of Physiology, Loyola University of Chicago, Maywood, Illinois 60153, USA
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19
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Howard PL, Dally GY, Ditta SD, Austin RC, Worton RG, Klamut HJ, Ray PN. Dystrophin isoforms DP71 and DP427 have distinct roles in myogenic cells. Muscle Nerve 1999; 22:16-27. [PMID: 9883853 DOI: 10.1002/(sici)1097-4598(199901)22:1<16::aid-mus5>3.0.co;2-r] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Duchenne muscular dystrophy is caused by mutations in the dystrophin gene, a complex gene that generates a family of distinct isoforms. In immature muscle cells, two dystrophin isoforms are expressed, Dp427 and Dp71. To characterize the function of Dp71 in myogenesis, we have examined the expression of Dp71 in myogenic cells. The localization of Dp71 in these cells is distinct from the localization of Dp427. Whereas Dp427 localizes to focal adhesions and surface membrane during myogenesis, Dp71 localizes to stress fiberlike structures in myogenic cells. Biochemical fractionation of myogenic cells demonstrates that Dp71 cosediments with the actin bundles thus confirming this interaction. Furthermore, transfection of C2C12 myoblasts with constructs encoding Dp71 fused to green fluorescent protein targeted the protein to the actin microfilament bundles. These results demonstrate involvement of Dp71 with the actin cytoskeleton during myogenesis and suggest a role for Dp71 that is distinct from Dp427.
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Affiliation(s)
- P L Howard
- Department of Molecular and Medical Genetics, University of Toronto, Canada
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20
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Potter GS, Johnson RJ, Fink GD. Role of endothelin in hypertension of experimental chronic renal failure. Hypertension 1997; 30:1578-84. [PMID: 9403586 DOI: 10.1161/01.hyp.30.6.1578] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Surgical ablation of renal mass leads to a reduction in kidney function and commonly to the development of hypertension and chronic renal failure (CRF) in rats. The objective of this study was to determine whether endothelin (ET)-1 is involved in the maintenance of the hypertension that accompanies loss of renal mass. First, we demonstrated the antihypertensive efficacy of PD 155080, a selective, orally active ET(A) receptor antagonist, in a group of rats made hypertensive by continuous intravenous infusion of ET-1 (2.5 pmol x kg(-1) x min[-1]) for 7 days. ET-1 produced a sustained hypertension and PD 155080 (56.4 micromol/kg [25mg/kg] BID PO) normalized blood pressure (BP) during the 5 days of drug administration. In a second experiment, Sprague-Dawley rats underwent a 5/6 reduction in renal mass (RRM); 4 weeks later, PD 155080 administered for 7 days resulted in a sustained reduction in BP. Sham-operated rats also showed a slight hypotensive response to PD 155080 administration. Plasma urea nitrogen, plasma creatinine, urinary protein excretion, and creatinine clearance were not altered by PD 155080 administration in RRM or sham rats. In a third experiment, we investigated the contribution of the renin-angiotensin system to BP control in RRM rats given PD 155080. In these rats, PD 155080 reduced BP during 5 treatment days, and this antihypertensive effect was not altered by coadministration of the angiotensin-converting enzyme inhibitor enalapril in the drinking water (508 micromol/L [250 mg/L]). These results demonstrate that (1) ET-1 plays a role in established RRM hypertension through activation of the ET(A) receptor subtype, (2) lowering blood pressure with PD 155080 in RRM rats does not adversely affect renal function, and 3) the antihypertensive effect of ET(A) receptor antagonism is not opposed by the renin-angiotensin system.
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Affiliation(s)
- G S Potter
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824-1317, USA
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21
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Rieder MJ, Roman RJ, Greene AS. Reversal of microvascular rarefaction and reduced renal mass hypertension. Hypertension 1997; 30:120-7. [PMID: 9231831 DOI: 10.1161/01.hyp.30.1.120] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This study examined the microcirculatory and renin-angiotensin system changes following the reversal of hypertension in reduced renal mass rats. Nine-week-old Sprague-Dawley reduced renal mass rats were placed on a low or high sodium diet for 4 or 8 weeks or a combination of 4 weeks of high sodium followed by 4 weeks of low sodium. Blood pressure was directly measured during the development of hypertension and its reversal. Plasma renin activity, angiotensin-converting enzyme activity, and angiotensin II concentrations were measured throughout the experiment. The cremaster and hindlimb muscles were removed, and microvascular density was determined by quantitative stereology. Four weeks of high sodium increased blood pressure (152+/-7 mm Hg) and reduced microvessel density (13.7%). Reduced renal mass hypertension was rapidly reversed after the rats were returned to a low sodium diet (124+/-7 mm Hg after 3 days), and microvascular density returned to control levels. After 4 weeks of high sodium, circulating plasma renin activity and angiotensin II fell by 94% and 82%, respectively. Plasma angiotensin-converting enzyme activity was increased after 2 weeks of high sodium but returned to control levels after 4 weeks of high sodium. This study demonstrates that microvascular density is reduced in reduced renal mass hypertensive rats following exposure to high sodium diet and this is associated with a fall in circulating plasma renin activity and angiotensin II levels. Microvascular density can return to normal levels after a reactivation of the circulating renin-angiotensin system. This study provides further evidence for the hypothesis that modulation of the renin-angiotensin system is important in the regulation of microvascular structure.
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Affiliation(s)
- M J Rieder
- Department of Physiology, Medical College of Wisconsin, Milwaukee 53226, USA
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22
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Abstract
Dystrophin is a key component of the subsarcolemmal skeleton of muscle cells, and lack of dystrophin is the direct cause of Duchenne muscular dystrophy. In skeletal muscle, dystrophin is reported to be localized specifically at costameres, transversely oriented riblike subsarcolemmal plaques that mechanically couple the contractile apparatus to the extracellular matrix. Costameres are characteristically rich in vinculin and are prominent in cardiac as well as skeletal muscle. To define the precise spatial relationship between dystrophin in relation to the costamere in cardiac muscle, we applied high-resolution single- and double-immunolabeling techniques, under a range of preparative conditions, with visualization of vinculin (as a costamere marker) and dystrophin by confocal microscopy and by the freeze-fracture cytochemical technique, fracture label. Immunoconfocal visualization revealed dystrophin as a continuous uniform layer at the cytoplasmic surface of the peripheral plasma membrane of the rat cardiac myocyte at both costameric and noncostameric regions. The pattern of labeling was reproducible with three different antibodies and was independent of time and antibody concentration. Platinum/carbon replicas and thin sections of fracture-label specimens permitted high-resolution visualization of the distribution of dystrophin in plane views of the freeze-fractured plasma membrane and in relation to the sarcomeric banding patterns of the underlying myofibrils. These results confirmed no preferential association of dystrophin with costameres or with any region of the sarcomeres of underlying myofibrils in rat cardiac tissue. We conclude that in contrast to skeletal muscle, dystrophin in cardiac muscle is not exclusively a component of the costamere.
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Affiliation(s)
- S Stevenson
- Imperial College School of Medicine, National Heart and Lung Institute, London, England
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23
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Brooks VL. Interactions between angiotensin II and the sympathetic nervous system in the the long-term control of arterial pressure. Clin Exp Pharmacol Physiol 1997; 24:83-90. [PMID: 9043811 DOI: 10.1111/j.1440-1681.1997.tb01788.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. The role of the renin-angiotensin system in long-term control of sympathetic activity and arterial pressure is reviewed. 2. There is evidence that favours a necessary role for the sympathetic nervous system in long-term arterial pressure regulation. First, appropriate changes in sympathetic activity appear to be produced in response to chronic changes in blood volume or blood pressure. Second, prevention of the normal homeostatic decrease in sympathetic activity in response to an increase in sodium intake produces hypertension. 3. Long-term changes in sympathetic activity cannot be mediated by the baroreceptor reflex, because it adapts to sustained changes in pressure. Therefore, an hypothesis is presented that evokes a key role for angiotensin II (AngII) in determining the chronic level of sympathetic activity. The key feature of this model is that the role of AngII is non-adaptive: chronic changes in extracellular fluid volume produce sustained reciprocal changes in AngII, and long-term increases in AngII produce sustained increases in sympathetic activity. 4. Evidence is reviewed that suggests that a lack of the normal suppression in AngII and/or sympathetic activity in response to an increase in sodium intake produces salt-sensitive hypertension.
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Affiliation(s)
- V L Brooks
- Department of Physiology and Pharmacology, Oregon Health Sciences University, Portland 97210-3098, USA
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24
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Meng H, Leddy JJ, Frank J, Holland P, Tuana BS. The association of cardiac dystrophin with myofibrils/Z-disc regions in cardiac muscle suggests a novel role in the contractile apparatus. J Biol Chem 1996; 271:12364-71. [PMID: 8647839 DOI: 10.1074/jbc.271.21.12364] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Dystrophin serves a variety of roles at the cell membrane through its associations, and defects in the dystrophin gene can give rise to muscular dystrophy and genetic cardiomyopathy. We investigated localization of cardiac dystrophin to determine potential intracellular sites of association. Subcellular fractionation revealed that while the majority of dystrophin was associated with the sarcolemma, about 35% of the 427-kDa form of dystrophin was present in the myofibrils. The dystrophin homolog utrophin was detectable only in the sarcolemmal membrane and was absent from the myofibrils as were other sarcolemmal glycoproteins such as adhalin and the sodium-calcium exchanger. Extraction of myofibrils with KC1 and detergents could not solubilize dystrophin. Dystrophin could only be dissociated from the myofibrillar protein complex in 5 M urea followed by sucrose density gradient centrifugation where it co-fractionated with one of two distinctly sedimenting peaks of actin. Immunoelectron microscopy of intracellular regions of cardiac muscle revealed a selective labeling of Z-discs by hystrophin antibodies. In the genetically determined cardiomyopathic hamster, strain CHF 147, the time course of development of cardiac insufficiency correlated with an overall 75% loss of myofibrillar dystrophin. These findings collectively show that a significant pool of the 427-kDa form of cardiac dystrophin was specifically associated with the contractile apparatus at the Z-discs, and its loss correlated with progression to cardiac insufficiency in genetic cardiomyopathy. The loss of distinct cellular pools of dystrophin may contribute to the tissue-specific pathophysiology in muscular dystrophy.
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Affiliation(s)
- H Meng
- Department of Pharmacology, University of Ottawa, Ontario, Canada
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25
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Satoh H, Delbridge LM, Blatter LA, Bers DM. Surface:volume relationship in cardiac myocytes studied with confocal microscopy and membrane capacitance measurements: species-dependence and developmental effects. Biophys J 1996; 70:1494-504. [PMID: 8785306 PMCID: PMC1225076 DOI: 10.1016/s0006-3495(96)79711-4] [Citation(s) in RCA: 243] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The quantitative analysis of the contribution of ion fluxes through membrane channels to changes of intracellular ion concentrations would benefit from the exact knowledge of the cell volume. It would allow direct correlation of ionic current measurements with simultaneous measurements of ion concentrations in individual cells. Because of various limitations of conventional light microscopy a simple method for accurate cell volume determination is lacking. We have combined the optical sectioning capabilities of fluorescence laser scanning confocal microscopy and the whole-cell patch-clamp technique to study the correlation between cell volume and membrane capacitance. Single cardiac myocytes loaded with the fluorescent dye calcein were optically sectioned to produce a series of confocal images. The volume of cardiac myocytes of three different mammalian species was determined by three-dimensional volume rendering of the confocal images. The calculated cell volumes were 30.4 +/- 7.3 pl (mean +/- SD) in rabbits (n = 28), 30.9 +/- 9.0 pl in ferrets (n = 23), and 34.4 +/- 7.0 pl in rats (n = 21), respectively. There was a positive linear correlation between membrane capacitance and cell volume in each animal species. The capacitance-volume ratios were significantly different among species (4.58 +/- 0.45 pF/pl in rabbit, 5.39 +/- 0.57 pF/pl in ferret, and 8.44 +/- 1.35 pF/pl in rat). Furthermore, the capacitance-volume ratio was dependent on the developmental stage (8.88 +/- 1.14 pF/pl in 6-month-old rats versus 6.76 +/- 0.62 pF/pl in 3-month-old rats). The data suggest that the ratio of surface area:volume of cardiac myocytes undergoes significant developmental changes and differs among mammalian species. We further established that the easily measurable parameters of cell membrane capacitance or the product of cell length and width provide reliable but species-dependent estimates for the volume of individual cells.
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Affiliation(s)
- H Satoh
- Department of Physiology, Loyola University Chicago, Maywood, Illinois 60153, USA
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26
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dos Remedios CG, Berry DA, Carter LK, Coumans JV, Heinke MY, Kiessling PC, Seeto RK, Thorvaldson T, Trahair T, Yeoh T, Yao M, Gunning PW, Hardeman E, Humphery-Smith I, Naidoo D, Keogh A. Different electrophoretic techniques produce conflicting data in the analysis of myocardial samples from dilated cardiomyopathy patients: protein levels do not necessarily reflect mRNA levels. Electrophoresis 1996; 17:235-8. [PMID: 8907547 DOI: 10.1002/elps.1150170140] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A variety of electrophoretic techniques were used to search for potential causes of human dilated cardiomyopathy (DCM). Northern blots were used to quantify alpha-cardiac and alpha-skeletal muscle actins, and beta-myosin heavy chain mRNAs which are the predominant expressed isoform species. We found a wide range of mRNA levels expressed in both DCM and nondiseased (ND) samples of left ventricles. However, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of the same heart samples revealed a stable and constant ratio of actin and myosin. Dystrophin deficiency might account for the DCM symptoms and so dystrophin levels of DCM and ND samples were evaluated using Western blots probed with monoclonal antibodies for the N-, C- and mid-rod portions of this protein. We found that dystrophin levels were constant in all 29 DCM and 5 ND samples suggesting that dystrophin deficiency is probably not a contributing cause. We explored the possibility that terminal failure may be due to an apoptotic-like event in the cardiomyocytes. Zymograms of DCM and ND samples revealed a significant increase in DNase I activity in the DCM group compared to the ND samples. These data raise the possibility that end-stage failure may be associated with apoptosis.
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Affiliation(s)
- C G dos Remedios
- Muscle Research Unit, Department of Anatomy, The University of Sydney, Australia.
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