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Casis O, Echeazarra L, Sáenz-Díez B, Gallego M. Deciphering the roles of triiodothyronine (T3) and thyroid-stimulating hormone (TSH) on cardiac electrical remodeling in clinical and experimental hypothyroidism. J Physiol Biochem 2024; 80:1-9. [PMID: 38019451 PMCID: PMC10808292 DOI: 10.1007/s13105-023-01000-z] [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: 06/15/2023] [Accepted: 11/20/2023] [Indexed: 11/30/2023]
Abstract
Hypothyroidism is the most frequent endocrine pathology. Although clinical or overt hypothyroidism has been traditionally associated to low T3 / T4 and high thyrotropin (TSH) circulating levels, other forms exist such as subclinical hypothyroidism, characterized by normal blood T3 / T4 and high TSH. In its different forms is estimated to affect approximately 10% of the population, especially women, in a 5:1 ratio with respect to men. Among its consequences are alterations in cardiac electrical activity, especially in the repolarization phase, which is accompanied by an increased susceptibility to cardiac arrhythmias. Although these alterations have traditionally been attributed to thyroid hormone deficiency, recent studies, both clinical trials and experimental models, demonstrate a fundamental role of TSH in cardiac electrical remodeling. Thus, both metabolic thyroid hormones and TSH regulate cardiac ion channel expression in many and varied ways. This means that the different combinations of hormones that predominate in different types of hypothyroidism (overt, subclinic, primary, central) can generate different forms of cardiac electrical remodeling. These new findings are raising the relevant question of whether serum TSH reference ranges should be redefined.
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Affiliation(s)
- Oscar Casis
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain.
| | - Leire Echeazarra
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain
| | - Beatriz Sáenz-Díez
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain
| | - Mónica Gallego
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain
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Gluvic Z, Obradovic M, Stewart AJ, Essack M, Pitt SJ, Samardzic V, Soskic S, Gojobori T, Isenovic ER. Levothyroxine Treatment and the Risk of Cardiac Arrhythmias - Focus on the Patient Submitted to Thyroid Surgery. Front Endocrinol (Lausanne) 2021; 12:758043. [PMID: 34803920 PMCID: PMC8600254 DOI: 10.3389/fendo.2021.758043] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/11/2021] [Indexed: 02/05/2023] Open
Abstract
Levothyroxine (LT4) is used to treat frequently encountered endocrinopathies such as thyroid diseases. It is regularly used in clinical (overt) hypothyroidism cases and subclinical (latent) hypothyroidism cases in the last decade. Suppressive LT4 therapy is also part of the medical regimen used to manage thyroid malignancies after a thyroidectomy. LT4 treatment possesses dual effects: substituting new-onset thyroid hormone deficiency and suppressing the local and distant malignancy spreading in cancer. It is the practice to administer LT4 in less-than-high suppressive doses for growth control of thyroid nodules and goiter, even in patients with preserved thyroid function. Despite its approved safety for clinical use, LT4 can sometimes induce side-effects, more often recorded with patients under treatment with LT4 suppressive doses than in unintentionally LT4-overdosed patients. Cardiac arrhythmias and the deterioration of osteoporosis are the most frequently documented side-effects of LT4 therapy. It also lowers the threshold for the onset or aggravation of cardiac arrhythmias for patients with pre-existing heart diseases. To improve the quality of life in LT4-substituted patients, clinicians often prescribe higher doses of LT4 to reach low normal TSH levels to achieve cellular euthyroidism. In such circumstances, the risk of cardiac arrhythmias, particularly atrial fibrillation, increases, and the combined use of LT4 and triiodothyronine further complicates such risk. This review summarizes the relevant available data related to LT4 suppressive treatment and the associated risk of cardiac arrhythmia.
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Affiliation(s)
- Zoran Gluvic
- Clinic for Internal Medicine, Department of Endocrinology and Diabetes, Zemun Clinical Hospital, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Milan Obradovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Alan J. Stewart
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Magbubah Essack
- King Abdullah University of Science and Technology (KAUST), Computer, Electrical, and Mathematical Sciences and Engineering (CEMSE) Division, Computational Bioscience Research Center (CBRC), Thuwal, Saudi Arabia
| | - Samantha J. Pitt
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Vladimir Samardzic
- Clinic for Internal Medicine, Department of Endocrinology and Diabetes, Zemun Clinical Hospital, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Sanja Soskic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Takashi Gojobori
- King Abdullah University of Science and Technology (KAUST), Computer, Electrical, and Mathematical Sciences and Engineering (CEMSE) Division, Computational Bioscience Research Center (CBRC), Thuwal, Saudi Arabia
| | - Esma R. Isenovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
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Tribulova N, Kurahara LH, Hlivak P, Hirano K, Szeiffova Bacova B. Pro-Arrhythmic Signaling of Thyroid Hormones and Its Relevance in Subclinical Hyperthyroidism. Int J Mol Sci 2020; 21:ijms21082844. [PMID: 32325836 PMCID: PMC7215427 DOI: 10.3390/ijms21082844] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/06/2020] [Accepted: 04/17/2020] [Indexed: 12/18/2022] Open
Abstract
A perennial task is to prevent the occurrence and/or recurrence of most frequent or life-threatening cardiac arrhythmias such as atrial fibrillation (AF) and ventricular fibrillation (VF). VF may be lethal in cases without an implantable cardioverter defibrillator or with failure of this device. Incidences of AF, even the asymptomatic ones, jeopardize the patient's life due to its complication, notably the high risk of embolic stroke. Therefore, there has been a growing interest in subclinical AF screening and searching for novel electrophysiological and molecular markers. Considering the worldwide increase in cases of thyroid dysfunction and diseases, including thyroid carcinoma, we aimed to explore the implication of thyroid hormones in pro-arrhythmic signaling in the pathophysiological setting. The present review provides updated information about the impact of altered thyroid status on both the occurrence and recurrence of cardiac arrhythmias, predominantly AF. Moreover, it emphasizes the importance of both thyroid status monitoring and AF screening in the general population, as well as in patients with thyroid dysfunction and malignancies. Real-world data on early AF identification in relation to thyroid function are scarce. Even though symptomatic AF is rare in patients with thyroid malignancies, who are under thyroid suppressive therapy, clinicians should be aware of potential interaction with asymptomatic AF. It may prevent adverse consequences and improve the quality of life. This issue may be challenging for an updated registry of AF in clinical practice. Thyroid hormones should be considered a biomarker for cardiac arrhythmias screening and their tailored management because of their multifaceted cellular actions.
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Affiliation(s)
- Narcis Tribulova
- Centre of Experimental Medicine, Slovak Academy of Sciences, Institute for Heart Research, 84104 Bratislava, Slovakia
- Correspondence: (N.T.); (B.S.B.); Tel.: +421-2-32295-423 (B.S.B.)
| | - Lin Hai Kurahara
- Department of Cardiovascular Physiology, Faculty of Medicine, Kagawa University, Kagawa 76 0793, Japan; (L.H.K.); (K.H.)
| | - Peter Hlivak
- Department of Arrhythmias and Pacing, National Institute of Cardiovascular Diseases, Pod Krásnou Hôrkou 1, 83348 Bratislava, Slovakia;
| | - Katsuya Hirano
- Department of Cardiovascular Physiology, Faculty of Medicine, Kagawa University, Kagawa 76 0793, Japan; (L.H.K.); (K.H.)
| | - Barbara Szeiffova Bacova
- Centre of Experimental Medicine, Slovak Academy of Sciences, Institute for Heart Research, 84104 Bratislava, Slovakia
- Correspondence: (N.T.); (B.S.B.); Tel.: +421-2-32295-423 (B.S.B.)
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Fernandez-Ruocco J, Gallego M, Rodriguez-de-Yurre A, Zayas-Arrabal J, Echeazarra L, Alquiza A, Fernández-López V, Rodriguez-Robledo JM, Brito O, Schleier Y, Sepulveda M, Oshiyama NF, Vila-Petroff M, Bassani RA, Medei EH, Casis O. High Thyrotropin Is Critical for Cardiac Electrical Remodeling and Arrhythmia Vulnerability in Hypothyroidism. Thyroid 2019; 29:934-945. [PMID: 31084419 PMCID: PMC6648210 DOI: 10.1089/thy.2018.0709] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Background: Hypothyroidism, the most common endocrine disease, induces cardiac electrical remodeling that creates a substrate for ventricular arrhythmias. Recent studies report that high thyrotropin (TSH) levels are related to cardiac electrical abnormalities and increased mortality rates. The aim of the present work was to investigate the direct effects of TSH on the heart and its possible causative role in the increased incidence of arrhythmia in hypothyroidism. Methods: A new rat model of central hypothyroidism (low TSH levels) was created and characterized together with the classical propylthiouracil-induced primary hypothyroidism model (high TSH levels). Electrocardiograms were recorded in vivo, and ionic currents were recorded from isolated ventricular myocytes in vitro by the patch-clamp technique. Protein and mRNA were measured by Western blot and quantitative reverse transcription polymerase chain reaction in rat and human cardiac myocytes. Adult human action potentials were simulated in silico to incorporate the experimentally observed changes. Results: Both primary and central hypothyroidism models increased the L-type Ca2+ current (ICa-L) and decreased the ultra-rapid delayed rectifier K+ current (IKur) densities. However, only primary but not central hypothyroidism showed electrocardiographic repolarization abnormalities and increased ventricular arrhythmia incidence during caffeine/dobutamine challenge. These changes were paralleled by a decrease in the density of the transient outward K+ current (Ito) in cardiomyocytes from animals with primary but not central hypothyroidism. In vitro treatment with TSH for 24 hours enhanced isoproterenol-induced spontaneous activity in control ventricular cells and diminished Ito density in cardiomyocytes from control and central but not primary hypothyroidism animals. In human myocytes, TSH decreased the expression of KCND3 and KCNQ1, Ito, and the delayed rectifier K+ current (IKs) encoding proteins in a protein kinase A-dependent way. Transposing the changes produced by hypothyroidism and TSH to a computer model of human ventricular action potential resulted in enhanced occurrence of early afterdepolarizations and arrhythmia mostly in primary hypothyroidism, especially under β-adrenergic stimulation. Conclusions: The results suggest that suppression of repolarizing K+ currents by TSH underlies most of the electrical remodeling observed in hypothyroidism. This work demonstrates that the activation of the TSH-receptor/protein kinase A pathway in the heart is responsible for the cardiac electrical remodeling and arrhythmia generation seen in hypothyroidism.
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Affiliation(s)
- Julieta Fernandez-Ruocco
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janerio, Brazil
- Centro de Investigaciones Cardiovasculares, Conicet La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Buenos Aires, Argentina
| | - Monica Gallego
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Ainhoa Rodriguez-de-Yurre
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janerio, Brazil
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Julian Zayas-Arrabal
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Leyre Echeazarra
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Amaia Alquiza
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Victor Fernández-López
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Juan M. Rodriguez-Robledo
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - Oscar Brito
- National Institute of Cardiology (INC), Rio de Janeiro, Brazil
| | - Ygor Schleier
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janerio, Brazil
| | - Marisa Sepulveda
- Centro de Investigaciones Cardiovasculares, Conicet La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Buenos Aires, Argentina
| | | | - Martin Vila-Petroff
- Centro de Investigaciones Cardiovasculares, Conicet La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Buenos Aires, Argentina
| | - Rosana A. Bassani
- Center for Biomedical Engineering, University of Campinas, Campinas, Brazil
| | - Emiliano H. Medei
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janerio, Brazil
| | - Oscar Casis
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
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Vieira FF, Olivoto RR, Silva POD, Francisco JC, Fogaça RTH. Functional Effects of Hyperthyroidism on Cardiac Papillary Muscle in Rats. Arq Bras Cardiol 2017; 107:542-549. [PMID: 28558076 PMCID: PMC5210458 DOI: 10.5935/abc.20160179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 06/27/2016] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Hyperthyroidism is currently recognized to affect the cardiovascular system, leading to a series of molecular and functional changes. However, little is known about the functional influence of hyperthyroidism in the regulation of cytoplasmic calcium and on the sodium/calcium exchanger (NCX) in the cardiac muscle. OBJECTIVES To evaluate the functional changes in papillary muscles isolated from animals with induced hyperthyroidism. METHODS We divided 36 Wistar rats into a group of controls and another of animals with hyperthyroidism induced by intraperitoneal T3 injection. We measured in the animals' papillary muscles the maximum contraction force, speed of contraction (+df/dt) and relaxation (-df/dt), contraction and relaxation time, contraction force at different concentrations of extracellular sodium, post-rest potentiation (PRP), and contraction force induced by caffeine. RESULTS In hyperthyroid animals, we observed decreased PRP at all rest times (p < 0.05), increased +df/dt and -df/dt (p < 0.001), low positive inotropic response to decreased concentration of extracellular sodium (p < 0.001), reduction of the maximum force in caffeine-induced contraction (p < 0.003), and decreased total contraction time (p < 0.001). The maximal contraction force did not differ significantly between groups (p = 0.973). CONCLUSION We hypothesize that the changes observed are likely due to a decrease in calcium content in the sarcoplasmic reticulum, caused by calcium leakage, decreased expression of NCX, and increased expression of a-MHC and SERCA2.
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Affiliation(s)
| | - Robson Ruiz Olivoto
- Laboratório de Fisiologia da Contração Muscular, Universidade Federal do Paraná, Brazil
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Alonso H, Fernández-Ruocco J, Gallego M, Malagueta-Vieira LL, Rodríguez-de-Yurre A, Medei E, Casis O. Thyroid stimulating hormone directly modulates cardiac electrical activity. J Mol Cell Cardiol 2015; 89:280-6. [PMID: 26497403 DOI: 10.1016/j.yjmcc.2015.10.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 10/02/2015] [Accepted: 10/19/2015] [Indexed: 11/29/2022]
Abstract
BACKGROUND The electrocardiogram of hypothyroid patients shows a series of abnormalities of cardiac repolarization due to a reduction of some repolarizing K(+) currents and an increase of the L-type calcium current. Experimental and clinical works call into question the unique role of T3 and T4 in these mechanisms and correlate increased serum TSH levels with the repolarization abnormalities in patients with both subclinical and overt hypothyroidism. In this context, the aim of the present study was to investigate the direct effects of TSH upon cardiac electrical properties. METHODS The action potential recording and the ion channel subunits mRNA expression were obtained from left ventricle of adult rats. Additionally, the repolarizing K(+) currents and the L-type Ca(2+) current (ICa-L) were recorded in isolated rat adult ventricular myocytes by the patch-clamp technique. RESULTS 24h exposure to TSH lengthened the action potential and slightly depolarized the resting membrane potential. TSH- receptor activation causes a reduction of the amplitude of Ito and IK1 currents caused by a reduction in channels expression. However, TSH had no effect on ICa-L, IK or IKur. CONCLUSION These results support the idea that some of the electrical disturbances seen in hypothyroid hearts, such as the Ito and IK1 current reduction, could be caused not by low T3 but by the elevation of circulating TSH.
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Affiliation(s)
- H Alonso
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - J Fernández-Ruocco
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil
| | - M Gallego
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - L L Malagueta-Vieira
- Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, Brazil
| | - A Rodríguez-de-Yurre
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain
| | - E Medei
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil
| | - O Casis
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco UPV/EHU, Vitoria, Spain.
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Axelband F, Dias J, Ferrão FM, Einicker-Lamas M. Nongenomic signaling pathways triggered by thyroid hormones and their metabolite 3-iodothyronamine on the cardiovascular system. J Cell Physiol 2010; 226:21-8. [PMID: 20658515 DOI: 10.1002/jcp.22325] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- F Axelband
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
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Thyroid hormones and cardiac arrhythmias. Vascul Pharmacol 2009; 52:102-12. [PMID: 19850152 DOI: 10.1016/j.vph.2009.10.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 10/05/2009] [Indexed: 01/09/2023]
Abstract
Thyroid hormone plays an important role in cardiac electrophysiology and Ca2+ handling through both genomic and nongenomic mechanisms of action, while both actions can interfere. Chronic changes in the amount of circulating thyroid hormone due to thyroid dysfunction or systemic disease result in structural, electrophysiological and Ca2+ handling remodeling, while acute changes may affect basal activity of cardiac cells membrane systems. Consequently, long-term or rapid modulation of sarcolemmal ion channels, Ca2+ cycling proteins and intercellular communicating channels by thyroid hormone may affect heart function as well as susceptibility of the heart to arrhythmias. This aspect including pro- and anti-arrhythmic potential of thyroid hormone is highlighted in this review.
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Effects of angiotensin II blockade on inflammation-induced alterations of pharmacokinetics and pharmacodynamics of calcium channel blockers. Br J Pharmacol 2007; 153:90-9. [PMID: 17965735 DOI: 10.1038/sj.bjp.0707538] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Inflammation elevates plasma verapamil concentrations but diminishes pharmacological response. Angiotensin II is a pro-inflammatory mediator. We examined the effect of angiotensin II receptor blockade on the pharmacokinetics and pharmacodynamics of verapamil, as well as the binding properties and amounts of its target protein in calcium channels, in a rat model of inflammation. EXPERIMENTAL APPROACH We used 4 groups of male Sprague-Dawley rats (220-280 g): inflamed-placebo, inflamed-treated, control-placebo and control-treated. Inflammation as pre-adjuvant arthritis was induced by injecting Mycobacterium butyricum on day 0. From day 6 to 12, 30 mg kg(-1) oral valsartan or placebo was administered twice daily. On day 12, a single oral dose of 25 mg kg(-1) verapamil was administered and prolongation of the PR interval measured and plasma samples collected for verapamil and nor-verapamil analysis. The amounts of the target protein Ca(v)1.2 subunit of L-type calcium channels in heart was measured by Western blotting and ligand binding with (3)H-nitrendipine. KEY RESULTS Inflammation reduced effects of verapamil, although plasma drug concentrations were increased. This was associated with a reduction in ligand binding capacity and amount of the calcium channel target protein in heart extracts. Valsartan significantly reversed the down-regulating effect of inflammation on verapamil's effects on the PR interval, and the lower level of protein binding and the decreased target protein. CONCLUSIONS AND IMPLICATIONS Reduced responses to calcium channel blockers in inflammatory conditions appeared to be due to a reduced amount of target protein that was reversed by the angiotensin II antagonist, valsartan.
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Tang NLS, Chow CC, Ko GTC, Tai MHL, Kwok R, Yao XQ, Cockram CS. The alpha(1S) subunit of the L-type calcium channel is not a predisposition gene for thyrotoxic periodic paralysis. Clin Endocrinol (Oxf) 2007; 66:229-34. [PMID: 17223993 DOI: 10.1111/j.1365-2265.2006.02713.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Thyrotoxic periodic paralysis (TTP) has been associated with genetic variations in the gene encoding the alpha 1 subunit of the L-type calcium channel (CACNA1S). Mutations in CACNA1S are known to account for the majority of cases of familial hypokalaemic periodic paralysis (HOKPP). In this study we have examined 48 genetic polymorphisms in the CACNA1S gene and genotyped a tagging set of representative polymorphisms to determine the role of this gene in TPP. DESIGN AND PATIENTS A genetic association study was carried out with 98 TPP patients and 162 male thyrotoxic controls. Among 47 polymorphisms evaluated for linkage disequilibrium (LD) and the spectrum of haplotypes in the Chinese population, 31 were selected as tagging single-nucleotide polymorphisms (SNPs) for genotyping the whole sample. A new genotyping protocol was used to analyse an insertion/deletion (I/D) polymorphism. RESULTS We studied the LD among 47 polymorphisms in the CACNA1S gene, which comprised a set of high-density markers with an average of one SNP every 2 kb. Subsequently, 31 tagSNPs were genotyped for all the samples. The gene is composed of three LD blocks. With this block structure, we were confident that variations of the gene were comprehensively covered by the tagSNPs. No significant association was found between the polymorphisms and TPP. CONCLUSION We established the LD structure of this calcium channel subunit gene (CACNA1S) for the first time. However, its genetic variations are not associated with TPP in Chinese patients.
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Affiliation(s)
- Nelson L S Tang
- Department of Chemical Pathology, Faculty of Medicine, The Chinese Univerisity of Hong Kong SAR, China.
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12
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Zamoner A, Royer C, Barreto KP, Pessoa-Pureur R, Silva FRMB. Ionic involvement and kinase activity on the mechanism of nongenomic action of thyroid hormones on 45Ca2+ uptake in cerebral cortex from young rats. Neurosci Res 2007; 57:98-103. [PMID: 17067709 DOI: 10.1016/j.neures.2006.09.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Revised: 09/14/2006] [Accepted: 09/20/2006] [Indexed: 11/24/2022]
Abstract
Thyroid hormones (TH) play important roles in brain development. Although most of the nongenomic actions of TH are known to be calcium-dependent, the effects of 3,5,3'-triiodo-L-thyronine (T(3)) or thyroxine (T(4)) on calcium influx in cerebral cortex of rats are not clear. In this study we investigate some mechanisms involved in the effect of T(3) and T(4) on Ca(2+) uptake in slices of cerebral cortex from 10-day-old male rats. Results indicated 10(-6)M T(3) or 10(-7)M T(4) was able to increase (45)Ca(2+) uptake after 30s of hormone exposure. The involvement of L- and T-type voltage-dependent Ca(2+) channels (VDCC) on the effect of TH on (45)Ca(2+) uptake was evidenced by using nifedipine and flunarizine, L- and T-type channel blockers, respectively. Otherwise, chloride currents were not involved in the hormone actions, as demonstrated by using 9-anthracene carboxylic acid, a Cl(-)-channel blocker. In addition, results demonstrated a PKC-dependent mechanism for both T(3) and T(4), as evidenced by stearoylcarnitine chloride, a specific PKC inhibitor. Furthermore, we verified that the T(3) action was also mediated by PKA activity, as demonstrated coincubating T(3) and KT 5720 (PKA inhibitor), and reinforced by using theophylline, a phosphodiesterase inhibitor. In contrast, concerning the effect of T(4), results suggest a partial involvement of PKA activity, and demonstrated that high cAMP levels were not able to support the effect of T(4), suggesting the participation of G inhibitory protein-coupled receptor in the action of this hormone on (45)Ca(2+) uptake. In conclusion, our results evidence a nongenomic action of TH promoting Ca(2+) influx by ionic channels involving mechanisms dependent on kinase activities. It is possible that the modulation of Ca(2+) channels by kinase activities represent an important membrane action of TH signaling mechanism in the central nervous system during development.
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Affiliation(s)
- Ariane Zamoner
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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