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Dhalla NS, Mota KO, de Vasconcelos CML, Adameova A. Behavior of Hypertrophied Right Ventricle during the Development of Left Ventricular Failure Due to Myocardial Infarction. Int J Mol Sci 2024; 25:2610. [PMID: 38473855 DOI: 10.3390/ijms25052610] [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: 01/08/2024] [Revised: 02/07/2024] [Accepted: 02/20/2024] [Indexed: 03/14/2024] Open
Abstract
In order to determine the behavior of the right ventricle, we have reviewed the existing literature in the area of cardiac remodeling, signal transduction pathways, subcellular mechanisms, β-adrenoreceptor-adenylyl cyclase system and myocardial catecholamine content during the development of left ventricular failure due to myocardial infarction. The right ventricle exhibited adaptive cardiac hypertrophy due to increases in different signal transduction pathways involving the activation of protein kinase C, phospholipase C and protein kinase A systems by elevated levels of vasoactive hormones such as catecholamines and angiotensin II in the circulation at early and moderate stages of heart failure. An increase in the sarcoplasmic reticulum Ca2+ transport without any changes in myofibrillar Ca2+-stimulated ATPase was observed in the right ventricle at early and moderate stages of heart failure. On the other hand, the right ventricle showed maladaptive cardiac hypertrophy at the severe stages of heart failure due to myocardial infarction. The upregulation and downregulation of β-adrenoreceptor-mediated signal transduction pathways were observed in the right ventricle at moderate and late stages of heart failure, respectively. The catalytic activity of adenylate cyclase, as well as the regulation of this enzyme by Gs proteins, were seen to be augmented in the hypertrophied right ventricle at early, moderate and severe stages of heart failure. Furthermore, catecholamine stores and catecholamine uptake in the right ventricle were also affected as a consequence of changes in the sympathetic nervous system at different stages of heart failure. It is suggested that the hypertrophied right ventricle may serve as a compensatory mechanism to the left ventricle during the development of early and moderate stages of heart failure.
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Affiliation(s)
- Naranjan S Dhalla
- Institute of Cardiovascular Sciences, St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, College of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Karina Oliveira Mota
- Heart Biophysics Laboratory, Department of Physiology, Center for Biological and Health Sciences, Federal University of Sergipe, São Cristóvão 49100-000, Brazil
| | - Carla Maria Lins de Vasconcelos
- Heart Biophysics Laboratory, Department of Physiology, Center for Biological and Health Sciences, Federal University of Sergipe, São Cristóvão 49100-000, Brazil
| | - Adriana Adameova
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Institute for Heart Research, Slovak Academy of Sciences, 8H103 Bratislava, Slovakia
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Kaykı-Mutlu G, Papazisi O, Palmen M, Danser AHJ, Michel MC, Arioglu-Inan E. Cardiac and Vascular α 1-Adrenoceptors in Congestive Heart Failure: A Systematic Review. Cells 2020; 9:E2412. [PMID: 33158106 PMCID: PMC7694190 DOI: 10.3390/cells9112412] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/29/2020] [Accepted: 11/02/2020] [Indexed: 02/07/2023] Open
Abstract
As heart failure (HF) is a devastating health problem worldwide, a better understanding and the development of more effective therapeutic approaches are required. HF is characterized by sympathetic system activation which stimulates α- and β-adrenoceptors (ARs). The exposure of the cardiovascular system to the increased locally released and circulating levels of catecholamines leads to a well-described downregulation and desensitization of β-ARs. However, information on the role of α-AR is limited. We have performed a systematic literature review examining the role of both cardiac and vascular α1-ARs in HF using 5 databases for our search. All three α1-AR subtypes (α1A, α1B and α1D) are expressed in human and animal hearts and blood vessels in a tissue-dependent manner. We summarize the changes observed in HF regarding the density, signaling and responses of α1-ARs. Conflicting findings arise from different studies concerning the influence that HF has on α1-AR expression and function; in contrast to β-ARs there is no consistent evidence for down-regulation or desensitization of cardiac or vascular α1-ARs. Whether α1-ARs are a therapeutic target in HF remains a matter of debate.
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Affiliation(s)
- Gizem Kaykı-Mutlu
- Department of Pharmacology, Faculty of Pharmacy, Ankara University, 06560 Ankara, Turkey; (G.K.-M.); (E.A.-I.)
| | - Olga Papazisi
- Department of Cardiothoracic Surgery, Leiden University Medical Center, 2300 RC Leiden, The Netherlands; (O.P.); (M.P.)
| | - Meindert Palmen
- Department of Cardiothoracic Surgery, Leiden University Medical Center, 2300 RC Leiden, The Netherlands; (O.P.); (M.P.)
| | - A. H. Jan Danser
- Department of Internal Medicine, Division of Pharmacology, Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands;
| | - Martin C. Michel
- Department of Pharmacology, Johannes Gutenberg University, 55131 Mainz, Germany
| | - Ebru Arioglu-Inan
- Department of Pharmacology, Faculty of Pharmacy, Ankara University, 06560 Ankara, Turkey; (G.K.-M.); (E.A.-I.)
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Mitra A, Basak T, Ahmad S, Datta K, Datta R, Sengupta S, Sarkar S. Comparative Proteome Profiling during Cardiac Hypertrophy and Myocardial Infarction Reveals Altered Glucose Oxidation by Differential Activation of Pyruvate Dehydrogenase E1 Component Subunit β. J Mol Biol 2014; 427:2104-20. [PMID: 25451023 DOI: 10.1016/j.jmb.2014.10.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 10/09/2014] [Accepted: 10/29/2014] [Indexed: 12/19/2022]
Abstract
Cardiac hypertrophy and myocardial infarction (MI) are two etiologically different disease forms with varied pathological characteristics. However, the precise molecular mechanisms and specific causal proteins associated with these diseases are obscure to date. In this study, a comparative cardiac proteome profiling was performed in Wistar rat models for diseased and control (sham) groups using two-dimensional difference gel electrophoresis followed by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry. Proteins were identified using Protein Pilot™ software (version 4.0) and were subjected to stringent statistical analysis. Alteration of key proteins was validated by Western blot analysis. The differentially expressed protein sets identified in this study were associated with different functional groups, involving various metabolic pathways, stress responses, cytoskeletal organization, apoptotic signaling and other miscellaneous functions. It was further deciphered that altered energy metabolism during hypertrophy in comparison to MI may be predominantly attributed to induced glucose oxidation level, via reduced phosphorylation of pyruvate dehydrogenase E1 component subunit β (PDHE1-B) protein during hypertrophy. This study reports for the first time the global changes in rat cardiac proteome during two etiologically different cardiac diseases and identifies key signaling regulators modulating ontogeny of these two diseases culminating in heart failure. This study also pointed toward differential activation of PDHE1-B that accounts for upregulation of glucose oxidation during hypertrophy. Downstream analysis of altered proteome and the associated modulators would enhance our present knowledge regarding altered pathophysiology of these two etiologically different cardiac disease forms.
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Affiliation(s)
- Arkadeep Mitra
- Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India
| | - Trayambak Basak
- Genomics and Molecular Medicine Unit, CSIR Institute of Genomics and Integrative Biology, Sukhdev Vihar, Mathura Road, New Delhi 110 020, India
| | - Shadab Ahmad
- Genomics and Molecular Medicine Unit, CSIR Institute of Genomics and Integrative Biology, Sukhdev Vihar, Mathura Road, New Delhi 110 020, India
| | - Kaberi Datta
- Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India
| | - Ritwik Datta
- Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India
| | - Shantanu Sengupta
- Genomics and Molecular Medicine Unit, CSIR Institute of Genomics and Integrative Biology, Sukhdev Vihar, Mathura Road, New Delhi 110 020, India
| | - Sagartirtha Sarkar
- Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India.
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Anversa P, Olivetti G. Cellular Basis of Physiological and Pathological Myocardial Growth. Compr Physiol 2011. [DOI: 10.1002/cphy.cp020102] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Abstract
While the remodeling process in myocardial failure involves changes in ventricular structure and performance, it is now appreciated that it is also associated with changes in thin filament composition and function. As is discussed, changes at the level thick filament may affect thin filament activation in heart failure. Alterations in actin, troponin and tropomyosin isoform composition do not appear to be significant factors in human heart failure. In contrast, proteolytic degradation of troponin subunits are likely to be playing a functional role in some forms of cardiomyopathy (e.g. ischemic). Finally, phosphorylation of troponin I and troponin T by kinases (most notably protein kinase C) substantially affect thin filament function in failing human myocardium. These findings indicate that functional deficits in thin filament function in failing myocardium are largely reversible and create the potential for future targeted therapies in the treatment of this deadly disease.
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Affiliation(s)
- Peter VanBuren
- Department of Medicine, College of Medicine, University of Vermont, VT 05405, USA.
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Konstam MA, Patten RD, Thomas I, Ramahi T, La Bresh K, Goldman S, Lewis W, Gradman A, Self KS, Bittner V, Rand W, Kinan D, Smith JJ, Ford T, Segal R, Udelson JE. Effects of losartan and captopril on left ventricular volumes in elderly patients with heart failure: results of the ELITE ventricular function substudy. Am Heart J 2000; 139:1081-7. [PMID: 10827391 DOI: 10.1067/mhj.2000.105302] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND The mechanism by which angiotensin-converting enzyme inhibitors reduce mortality rates and disease progression in patients with heart failure is likely mediated in part through prevention of adverse ventricular remodeling. This study examined the effects of the angiotensin-converting enzyme inhibitor captopril and the angiotensin II type 1 receptor antagonist losartan on ventricular volumes and function in elderly patients with heart failure and reduced left ventricular ejection fraction (< or =40%). METHODS Patients underwent radionuclide ventriculograms (RVG) at baseline and were randomized to either captopril (n = 16) or losartan (n = 13). After 48 weeks, another RVG was obtained. Therapy was then withdrawn for at least 5 days, and the RVG was repeated while the patient was not receiving the drug. RESULTS At 48 weeks both captopril and losartan significantly reduced left ventricular (LV) end-diastolic volume index (135 +/- 26 to 128 +/- 23 mL/m(2) for losartan, P <.05 vs baseline; 142 +/- 25 to 131 +/- 20 mL/m(2) for captopril, P <.01; mean (SD). Captopril also reduced LV end-systolic volume index (98 +/- 24 to 89 +/- 21 mL/m(2), P <.01 vs. baseline), whereas a nonsignificant trend was observed for the losartan group (97 +/- 23 to 90 +/- 16 mL/m(2), P = not significant). The between-group differences in the changes in LV volumes were not statistically significant. After drug withdrawal, LV end-diastolic volume index remained significantly lower than baseline in the captopril group (P <.01). CONCLUSIONS Both captopril and losartan prevent LV dilation, representing adverse ventricular remodeling, previously seen with placebo treatment. Reverse remodeling was observed in the captopril group. On the basis of these results, the relative effects on LV remodeling do not provide a rationale for a survival benefit of losartan over captopril.
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Affiliation(s)
- M A Konstam
- Tufts University, New England Medical Center, Boston, MA 02111, USA.
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Stanton LW, Garrard LJ, Damm D, Garrick BL, Lam A, Kapoun AM, Zheng Q, Protter AA, Schreiner GF, White RT. Altered patterns of gene expression in response to myocardial infarction. Circ Res 2000; 86:939-45. [PMID: 10807865 DOI: 10.1161/01.res.86.9.939] [Citation(s) in RCA: 257] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The use of cDNA microarrays has made it possible to simultaneously analyze gene expression for thousands of genes. Microarray technology was used to evaluate the expression of >4000 genes in a rat model of myocardial infarction. More than 200 genes were identified that showed differential expression in response to myocardial infarction. Gene expression changes were monitored from 2 to 16 weeks after infarction in 2 regions of the heart, the left ventricle free wall and interventricular septum. A novel clustering program was used to identify patterns of expression within this large set of data. Unique patterns were revealed within the transcriptional responses that illuminate changes in biological processes associated with myocardial infarction.
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Leri A, Liu Y, Malhotra A, Li Q, Stiegler P, Claudio PP, Giordano A, Kajstura J, Hintze TH, Anversa P. Pacing-induced heart failure in dogs enhances the expression of p53 and p53-dependent genes in ventricular myocytes. Circulation 1998; 97:194-203. [PMID: 9445173 DOI: 10.1161/01.cir.97.2.194] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Rapid ventricular pacing in dogs is characterized by a dilated myopathy in which myocyte cell death by apoptosis may play a significant role in the impairment of cardiac pump function. However, the molecular mechanisms implicated in the modulation of programmed cell death under this setting remain to be identified. Moreover, questions have been raised on the specificity and sensitivity of the histochemical detection of DNA strand breaks in nuclei by the terminal deoxynucleotidyl transferase (TdT) reaction. METHODS AND RESULTS Changes in the expression of Bcl-2 and Bax and their transcriptional regulator, p53, were determined by Western blot analysis in myocytes isolated from dogs affected by pacing-induced heart failure. A mobility shift assay for p53 binding activity was also performed. In addition, apoptosis was measured by confocal microscopy, which allowed the simultaneous detection of chromatin alterations and DNA damage. p53 DNA binding activity to the bax promoter was increased in nuclear extracts from myocytes obtained from failing hearts, and this response was associated with enhanced expression of Bax protein, 52%, and attenuation of Bcl-2, -92%. Immunolabeling of p53 in myocyte nuclei, measured by confocal microscopy, was 100% higher in cells from paced hearts. The combination of the TdT assay and confocal microscopy demonstrated that 20 myocyte nuclei per 10(6) were undergoing apoptosis in control myocardium and 4000 per l0(6) after pacing. Moreover, DNA laddering was shown in myocytes by agarose gel electrophoresis of DNA fragments. CONCLUSIONS The activation of p53 and p53-dependent genes may be critical in the modulation of myocyte apoptosis in pacing-induced heart failure.
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Affiliation(s)
- A Leri
- Department of Medicine, New York Medical College, Valhalla 10595, USA
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9
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Abstract
Heterotrimeric GTP-binding and -hydrolyzing proteins (G proteins) link members of a family of seven-helix transmembrane receptors (G protein-coupled receptors, GPCR) to intracellular effectors. The coupling mechanism involves the G protein completing a cycle of activation, dissociation into alpha and beta gamma subunits, deactivation, and reassociation. At the center of this cycle is the alpha subunit, in which activation by GPCR, GTPase activity, and regulation of effector are combined. Whereas G alpha's functional domains and residues had already been inferred from mutagenesis studies, the recent solution of the crystal structure has elucidated the structural basis of alpha subunit function. It is now clear that an irregularity in any GPCR pathway component could cause a physiological defect. This is confirmed by the identification of mutations in GPCR and G alpha's in various human diseases. Although several cardiomyopathies are associated with abnormal GPCR function, mutations are unlikely in these disorders. The last few years, other aspects of G protein function have moved into focus: e.g. posttranslational modifications; effector regulation by beta gamma subunits; GTPase activating protein (GAP) activity of effectors; G protein expression levels etc. When comparing the regulation of G protein functional activity in cAMP and in inositol phosphate generating pathways, an extrapolation can be made to data on the status of these pathways in some cardiovascular diseases.
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Affiliation(s)
- J T Meij
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041, USA
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Cheng W, Reiss K, Li P, Chun MJ, Kajstura J, Olivetti G, Anversa P. Aging does not affect the activation of the myocyte insulin-like growth factor-1 autocrine system after infarction and ventricular failure in Fischer 344 rats. Circ Res 1996; 78:536-46. [PMID: 8635210 DOI: 10.1161/01.res.78.4.536] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
To determine whether the attenuation in the growth capacity of myocytes in the overloaded aging heart is associated with an impairment in the activation of insulin-like growth factor-1 (IGF-1) and its receptor (IGF-1R) in the stressed cells, large myocardial infarcts were produced in Fischer 344 rats at 4 and 16 months of age, and the animals were killed 6 hours, 3 days, and 7 days later. After the documentation of cardiac failure, the unaffected myocytes were enzymatically dissociated, and the expression of IGF-1 and IGF-1R was measured at these three time points after surgery. The level of expression of IGF-1R mRNA increased at 3 days and remained elevated at 7 days in both age groups. In addition, an increase in IGF-1R protein in these cells was found, with no apparent difference with age. This phenomenon was coupled with an upregulation of IGF-1 mRNA of comparable magnitude in the younger and older animals. In contrast, the increases in the dimensional properties of myocytes were delayed and of smaller magnitude in the older infarcted rats. Moreover, the expression of atrial natriuretic factor, used as a molecular marker of myocyte cellular hypertrophy, was greater at 3 days in 4-month-old rats and at 7 days in 16-month-old rats. Thus, aging may affect the hypertrophic response of myocytes after infarction but has no impact on the ability of the cells to enhance the expression of IGF-1 and IGF-1R, which may sustain only in part the growth reserve mechanisms of the pathological heart.
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Affiliation(s)
- W Cheng
- Department of Medicine, New York Medical College, Valhalla 10595, USA
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Nio Y, Matsubara H, Murasawa S, Kanasaki M, Inada M. Regulation of gene transcription of angiotensin II receptor subtypes in myocardial infarction. J Clin Invest 1995; 95:46-54. [PMID: 7814645 PMCID: PMC295367 DOI: 10.1172/jci117675] [Citation(s) in RCA: 314] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Increasing evidence suggests that angiotensin II (AngII) acts as a modulator for ventricular remodeling after myocardial infarction. Using competitive reverse-transcriptase polymerase chain reaction, nuclear runoff, and binding assays, we examined the regulation of AngII type 1a and 1b (AT1a-R and AT1b-R) and type 2 receptor (AT2-R) expression in the infarcted rat heart as well as the effects of AngII receptor antagonists. AT1a-R mRNA levels were increased in the infarcted (4.2-fold) and noninfarcted portions (2.2-fold) of the myocardium 7 d after myocardial infarction as compared with those in sham-operated controls, whereas AT1b-R mRNA levels were unchanged. The amount of detectable AT2-R mRNA increased in infarcted (3.1-fold) and noninfarcted (1.9-fold) portions relative to that in the control. The transcription rates for AT1a-R and AT2-R genes, determined by means of a nuclear runoff assay, were significantly increased in the infarcted heart. The AngII receptor numbers were elevated (from 12 to 35 fmol/mg protein) in the infarcted myocardium in which the increases in AT1-R and AT2-R were 3.2- and 2.3-fold, respectively, while the receptor affinity was unchanged. Therapy with AT1-R antagonist for 7 d reduced the increase in AT1-R and AT2-R expressions in the infarcted heart together with a decrease in blood pressure, whereas therapy with an AT2-R antagonist did not affect mRNA levels and blood pressure. Neither AT1-R nor AT2-R antagonists affected the infarct sizes. These results demonstrated that myocardial infarction causes an increase in the gene transcription and protein expression of cardiac AT1a-R and AT2-R, whereas the AT1b-R gene is unaffected, and that therapy with an AT1-R antagonist, but not with an AT2-R antagonist, is effective in reducing the increased expression of AngII receptor subtypes induced by myocardial infarction.
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Affiliation(s)
- Y Nio
- Second Department of Internal Medicine, Kansai Medical University, Osaka, Japan
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Meggs LG, Coupet J, Huang H, Cheng W, Li P, Capasso JM, Homcy CJ, Anversa P. Regulation of angiotensin II receptors on ventricular myocytes after myocardial infarction in rats. Circ Res 1993; 72:1149-62. [PMID: 8495545 DOI: 10.1161/01.res.72.6.1149] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To determine the effects of acute myocardial infarction on the regulation of angiotensin II (Ang II) receptors and contractile performance of left and right ventricular myocytes, coronary artery ligation was surgically induced in rats, and Ang II receptor density and affinity and the mechanical properties of surviving muscle cells were examined 1 week later. Physiological determinations of cardiac pump function revealed the presence of ventricular failure, which was associated at the cellular level with a depression in the velocity of myocyte shortening and relengthening, a prolongation of time to peak shortening, and a reduction in the extent of cell shortening. These abnormalities in single-cell function were more prominent in left than in right ventricular myocytes. Cellular hypertrophy was documented by increases in cell length and width, which were also greater in the spared myocytes of the infarcted left ventricle. Reactive hypertrophy was accompanied by a 1.84- and 1.85-fold increase in the density of Ang II receptors on left and right myocytes, respectively. On the other hand, the affinity of Ang II receptors for the radiolabeled antagonist was not altered. However, Ang II-stimulated phosphoinositol turnover was enhanced by 3.7- and 2.5-fold in left and right myocytes, respectively, after infarction. Ventricular myocytes were found to possess the AT1 receptor subtype exclusively. In conclusion, myocardial infarction leads to impairment in the contractile behavior of the remaining cells and to the activation of Ang II receptors and effector pathway associated with these receptors, which may be involved in the reactive growth adaptation of the viable myocytes.
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Affiliation(s)
- L G Meggs
- Department of Medicine, New York Medical College, Valhalla 10595
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Meggs LG, Huang H, Li P, Capasso JM, Anversa P. Chronic nonocclusive coronary artery constriction in rats. Beta-adrenoceptor signal transduction and ventricular failure. J Clin Invest 1991; 88:1940-6. [PMID: 1661293 PMCID: PMC295773 DOI: 10.1172/jci115518] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
To determine the effects of chronic coronary artery constriction on the relationship between cardiac function and regulation of beta-adrenoceptor signal transduction, the left main coronary artery was narrowed in rats and the animals were killed 5 mo later. An average reduction in coronary luminal diameter of 44% was obtained and this change resulted in an increase in left ventricular end-diastolic pressure and a decrease in positive and negative dP/dt. Significant increases in left and right ventricular weights indicative of global cardiac hypertrophy were observed. Radioligand binding studies of beta-adrenoreceptors, agonist-stimulated adenylate cyclase activity, and ADP ribosylation of 45-kD substrate by cholera toxin were all depressed in the failing left ventricle. In contrast, in the hypertrophic non-failing right ventricle, beta-adrenoreceptor density was preserved and receptor antagonist affinity was increased. In spite of these findings at the receptor level, agonist stimulated cyclic AMP generation was reduced in the right ventricular myocardium. The quantity of the 45-kD substrate was also decreased. In conclusion, longterm nonocclusive coronary artery stenosis of moderate degree has profound detrimental effects on the contractile performance of the heart in association with marked attenuation of adrenergic support mechanisms.
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Affiliation(s)
- L G Meggs
- Department of Medicine, New York Medical College, Valhalla 10595
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Abstract
To determine whether myocyte mitotic division occurs in the adult mammalian heart and whether this cellular process is affected by aging, we measured the percentage of myocyte nuclei showing metaphase chromosomes in myocytes isolated from the left and right ventricles of rats at 8-12, 19-24, and 28-32 months after birth. Metaphase chromosomes were found at all ages in both ventricles. However, from 8-12 to 28-32 months, the fraction of nuclei exhibiting metaphase chromosomes increased 6.3-fold and 2.3-fold in the left and right ventricles, respectively. Thus, myocyte cellular hyperplasia is present in the adult and aging myocardium as a compensatory mechanism to regenerate tissue mass and recover function, which are lost with the progression of life and senescence.
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Affiliation(s)
- P Anversa
- Department of Medicine, New York Medical College, Valhalla 10595
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