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Pulmonary veins (PV) are the main source of ectopy, triggering atrial fibrillation. This study investigated the roles of G protein-coupled inwardly rectifying potassium (GIRK) channels in the PV and the left atrium (LA) of the rat. Simultaneous intracellular microelectrode recording from the LA and the PV of the rat found that in the presence or absence of acetylcholine, the GIRK channel blocker tertiapin-Q induced AP duration elongation in the LA and the loss of over-shooting AP in the PV, suggesting the presence of constitutively active GIRK channels in these tissues. Patch-clamp recordings from isolated myocytes showed that tertiapin-Q inhibited a basal inwardly rectified background current in PV cells with little effect in LA cells. Experiments with ROMK1 and KCa1.1 channel blockers ruled out the possibility of an off-target effect. Western blot showed that GIRK4 subunit expression was greater in PV cardiomyocytes, which may explain the differences observed between PV and LA in response to tertiapin-Q. In conclusion, GIRK channels blockade abolishes AP only in the PV, providing a molecular target to induce electrical disconnection of the PV from the LA.
Assuntos
Fibrilação Atrial , Veias Pulmonares , Animais , Ratos , Acetilcolina , Western Blotting , Miócitos CardíacosRESUMO
INTRODUCTION AND OBJECTIVE: Nowadays, investigations of heart physiology and pathophysiology rely more and more upon image analysis, whether for the detection and characterization of events in single cells or for the mapping of events and their characteristics across an entire tissue. These investigations require extensive skills in image analysis and/or expensive software, and their reproducibility may be a concern. Our objective was to build a robust, reliable and open-source software tool to quantify excitation-contraction related experimental data at multiple scales, from single isolated cells to the whole heart. METHODS AND RESULTS: A free and open-source ImageJ plugin, Spiky, was developed to detect and analyze peaks in experimental data streams. It allows rapid and easy analysis of action potentials, intracellular calcium transient and contraction data from cardiac research experiments. As shown in the provided examples, both classical bi-dimensional data (XT signals) and video data obtained from confocal microscopy and optical mapping experiments (XYT signals) can be analyzed. Spiky was written in ImageJ Macro Language and JAVA, and works under Windows, Mac and Linux operating systems. CONCLUSION: Spiky provides a complete working interface to process and analyze cardiac physiology research data.
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INTRODUCTION: Gabapentinoids are ligands of the α2-δ subunit of voltage-gated calcium channels (Cav) that have been associated with a risk of peripheral edema and acute heart failure in connection with a potentially dual mechanism, vascular and cardiac. OBJECTIVES & METHODS: All cases of peripheral edema or heart failure involving gabapentin or pregabalin reported to the French Pharmacovigilance Centers between January 1, 1994 and April 30, 2020 were included to describe their onset patterns (e.g., time to onset). Based on these data, we investigated the impact of gabapentinoids on the myogenic tone of rat third-order mesenteric arteries and on the electrophysiological properties of rat ventricular cardiomyocytes. RESULTS: A total of 58 reports were included (gabapentin n = 5, pregabalin n = 53). The female-to-male ratio was 4:1 and the median age was 77 years (IQR 57-85, range 32-95). The median time to onset were 23 days (IQR 10-54) and 17 days (IQR 3-30) for non-cardiogenic edema and acute heart failure, respectively. Cardiogenic and non-cardiogenic peripheral edema occurred frequently after a dose escalation (27/45, 60%), and the course was rapidly favorable after discontinuation of gabapentinoid (median 7 days, IQR 5-13). On rat mesenteric arteries, gabapentinoids significantly decreased the myogenic tone to the same extent as verapamil and nifedipine. Acute application of gabapentinoids had no significant effect on Cav1.2 currents of ventricular cardiomyocytes. CONCLUSION: Gabapentinoids can cause concentration-dependent peripheral edema of early onset. The primary mechanism of non-cardiogenic peripheral edema is vasodilatory edema secondary to altered myogenic tone, independent of Cav1.2 blockade under the experimental conditions tested.
Assuntos
Edema , Gabapentina , Insuficiência Cardíaca , Idoso , Idoso de 80 Anos ou mais , Experimentação Animal , Animais , Edema/induzido quimicamente , Feminino , Gabapentina/efeitos adversos , Insuficiência Cardíaca/induzido quimicamente , Humanos , Masculino , Pessoa de Meia-Idade , Farmacovigilância , Pregabalina/efeitos adversos , RatosRESUMO
The modulation of SK3 ion channels can be efficiently and selectively achieved by using the amphiphilic compound Ohmline (a glyco-glycero-ether-lipid). We report herein a series of Ohmline analogues featuring the replacement of one ether function by a thioether function located at the same position or shifted close to its initial position. The variation of the lipid chain length and the preparation of two analogues featuring either one sulfoxide or one sulfone moiety complete this series. Patch clamp measurements indicate that the presence of the thioether function (compounds 7 and 17a) produces strong activators of SK3 channels, whereas the introduction of a sulfoxide or a sulfone function at the same place produces amphiphiles devoid of an effect on SK3 channels. Compounds 7 and 17a are the first amphiphilic compounds featuring strong activation of SK3 channels (close to 200% activation). The cytosolic calcium concentration determined from fluorescence at 3 different times for compound 7b (13 min, 1 h, 24 h) revealed that the effect is different suggesting that the compound could be metabolized over time. This compound could be used as a strong SK3 activator for a short time. The capacity of 7b to activate SK3 was then used to induce vasorelaxation via an endothelium-derived hyperpolarization (EDH) pathway. For the first time, we report that an amphiphilic compound can affect the endothelium dependent vasorelaxation.
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Éteres/farmacologia , Glicolipídeos/farmacologia , Canais de Potássio Ativados por Cálcio de Condutância Baixa/metabolismo , Compostos de Sulfidrila/farmacologia , Tensoativos/farmacologia , Animais , Movimento Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Éteres/química , Glicolipídeos/química , Humanos , Masculino , Ratos , Ratos Wistar , Compostos de Sulfidrila/química , Tensoativos/síntese química , Tensoativos/química , Vasodilatação/efeitos dos fármacosRESUMO
Ectopic activity in the pulmonary vein cardiac muscle sleeves can both induce and maintain human atrial fibrillation. A central issue in any study of the pulmonary veins is their difference from the left atrial cardiac muscle. Here, we attempt to summarize the physiological phenomena underlying the occurrence of ectopic electrical activity in animal pulmonary veins. We emphasize that the activation of multiple signaling pathways influencing not only myocyte electrophysiology but also the means of excitation-contraction coupling may be required for the initiation of triggered or automatic activity. We also gather information regarding not only the large-scale structure of cardiac muscle sleeves but also recent studies suggesting that cellular heterogeneity may contribute to the generation of arrythmogenic phenomena and to the distinction between pulmonary vein and left atrial heart muscle.
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Fibrilação Atrial , Veias Pulmonares , Animais , Átrios do Coração , MiocárdioRESUMO
BACKGROUND/OBJECTIVES: Hibiscus sabdariffa L. (H. sabdariffa (HS)) extract has a vascular relaxant effect on isolated rat thoracic aorta, but data on small resistance arteries, which play an important role on the development of hypertension, are still missing. The purposes of this study were (1) to assess the effect on isolated mesenteric arteries (MA) from normotensive (Wistar and Wistar-Kyoto (WKY)) and spontaneous hypertensive rats (SHR); (2) to elucidate the mechanism(s) of action underling the relaxant effect in light of bioactive components. METHODS: Vascular effects of HS aqueous fraction (AF) on isolated MA rings, as well as its mechanisms of action, were assessed using the contractility and intracellular microelectrode technique. The patch clamp technique was used to evaluate the effect of HS AF on the L-type calcium current. Extraction and enrichment of AF were carried out using liquid-liquid extraction, and the yield was analyzed using HPLC. RESULTS: The HS AF induced a concentration-dependent relaxant effect on MA rings of SHR (EC50 = 0.83 ± 0.08 mg/mL), WKY (EC50 = 0.46 ± 0.04 mg/mL), and Wistar rats (EC50 = 0.44 ± 0.08 mg/mL) pre-contracted with phenylephrine (10 µM). In Wistar rats, the HS AF maximum relaxant effect was not modified after endothelium removal or when a guanylate cyclase inhibitor (ODQ, 10 µM) and a selective ß2-adrenergic receptor antagonist (ICI-118551, 1 µM) were incubated with the preparation. Otherwise, it was reduced by 34.57 ± 10.66% when vascular rings were pre-contracted with an 80 mM [K+] solution (p < 0.001), which suggests an effect on ionic channels. HS AF 2 mg/mL significantly decreased the peak of the L-type calcium current observed in cardiac myocytes by 24.4%. Moreover, though the vasorelaxant effect of HS, AF was reduced by 27% when the nonselective potassium channels blocker (tetraethylammonium (TEA) 20 mM) was added to the bath (p < 0.01). The extract did not induce a membrane hyperpolarization of smooth muscle cells, which might suggest an absence of a direct effect on background potassium current. CONCLUSION: These results highlight that the antihypertensive effect of HS probably involves a vasorelaxant effect on small resistance arteries, which is endothelium independent. L-type calcium current reduction contributes to this effect. The results could also provide a link between the vasorelaxant effect and the bioactive compounds, especially anthocyanins.
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Canais de Cálcio/efeitos dos fármacos , Hibiscus/química , Hipertensão/tratamento farmacológico , Artérias Mesentéricas/efeitos dos fármacos , Extratos Vegetais/farmacologia , Vasodilatadores/farmacologia , Animais , Anti-Hipertensivos/farmacologia , Canais de Cálcio/fisiologia , Flores , Hipertensão/fisiopatologia , Masculino , Artérias Mesentéricas/fisiopatologia , Técnicas de Patch-Clamp , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio/efeitos dos fármacos , Canais de Potássio/fisiologia , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
Pulmonary veins (PV) are involved in the pathophysiology of paroxysmal atrial fibrillation. In the rat, left atrium (LA) and PV cardiomyocytes have different reactions to α1-adrenergic receptor activation. In freely beating atria-PV preparations, we found that electrical field potential (EFP) originated from the sino-atrial node propagated through the LA and the PV. The α1-adrenergic receptor agonist cirazoline induced a progressive loss of EFP conduction in the PV whereas it was maintained in the LA. This could be reproduced in preparations electrically paced at 5 Hz in LA. During pacing at 10 Hz in the PV where high firing rate ectopic foci can occur, cirazoline stopped EFP conduction from the PV to the LA, which allowed the sino-atrial node to resume its pace-making function. Loss of conduction in the PV was associated with depolarization of the diastolic membrane potential of PV cardiomyocytes. Adenosine, which reversed the cirazoline-induced depolarization of the diastolic membrane potential of PV cardiomyocytes, restored full over-shooting action potentials and EFP conduction in the PV. In conclusion, selective activation of α1-adrenergic receptors results in the abolition of electrical conduction within the PV. These results highlight a potentially novel pharmacological approach to treat paroxysmal atrial fibrillation by targeting directly the PV myocardium.
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Fibrilação Atrial/fisiopatologia , Veias Pulmonares/metabolismo , Receptores Adrenérgicos alfa 1/metabolismo , Potenciais de Ação/fisiologia , Antagonistas de Receptores Adrenérgicos alfa 1/metabolismo , Antagonistas de Receptores Adrenérgicos alfa 1/farmacologia , Animais , Fibrilação Atrial/metabolismo , Condutividade Elétrica , Átrios do Coração/fisiopatologia , Sistema de Condução Cardíaco/fisiopatologia , Frequência Cardíaca , Masculino , Potenciais da Membrana , Miocárdio/patologia , Miócitos Cardíacos/patologia , Veias Pulmonares/fisiologia , Ratos , Ratos Wistar , Receptores Adrenérgicos alfa 1/fisiologia , Nó Sinoatrial/fisiopatologiaRESUMO
The composition of periprostatic adipose tissue (PPAT) has been shown to play a role in prostate cancer (PCa) progression. We recently reported an inverse association between PCa aggressiveness and elevated PPAT linoleic acid (LA) and eicosapentaenoic acid (EPA) content. In the present study, we identified a new signaling pathway with a positive feedback loop between the epithelial-to-mesenchymal transition (EMT) transcription factor Zeb1 and the Ca2+-activated K+ channel SK3, which leads to an amplification of Ca2+ entry and cellular migration. Using in vitro experiments and ex vivo cultures of human PCa slices, we demonstrated that LA and EPA exert anticancer effects, by modulating Ca2+ entry, which was involved in Zeb1 regulation and cancer cellular migration. This functional approach using human prostate tumors highlights the clinical relevance of our observations, and may allow us to consider the possibility of targeting cancer spread by altering the lipid microenvironment.
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In prostate cancer research, there is a lack of valuable preclinical models. Tumor cell heterogeneity and sensitivity to microenvironment signals, such as hypoxia or extracellular calcium concentration, are difficult to reproduce. Here, we developed and characterized an ex vivo tissue culture model preserving these properties. Prostate tissue slices from 26 patients were maintained ex vivo under optimized culture conditions. The expression of markers associated with proliferation, androgen-receptor signaling, and hypoxia was assessed by immunostaining. A macroscope was used to achieve real-time calcium fluorescence optical imaging. Tissue morphology was maintained successfully without necrosis for 5 days. Compared with native tumors and tissue cultured with androgens, androgen deprivation in the medium led to decreased expression of both androgen receptor and its target gene products, prostate specific antigen (PSA) and ETS-related gene (ERG). Ex vivo cultured slices also were sensitive to hypoxia because carbonic anhydrase IX and zinc finger E-box binding homeobox 1 (Zeb1) protein levels increased in 1% oxygen. Exposure of slices to supraphysiological extracellular Ca2+ concentration induced a robust and rapid Ca2+ entry, with a greater response in tumor compared with nontumor tissue. This ex vivo model reproduces the morphologic and functional characteristics of human prostate cancer, including sensitivity to androgen deprivation and induced response to hypoxia and extracellular Ca2+. It therefore could become an attractive tool for drug response prediction studies.
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Sinalização do Cálcio , Cálcio/metabolismo , Modelos Biológicos , Neoplasias da Próstata/metabolismo , Microambiente Tumoral , Idoso , Antígenos de Neoplasias/metabolismo , Anidrase Carbônica IX/metabolismo , Hipóxia Celular , Humanos , Calicreínas/metabolismo , Masculino , Pessoa de Meia-Idade , Proteínas de Neoplasias/metabolismo , Antígeno Prostático Específico/metabolismo , Neoplasias da Próstata/patologia , Neoplasias da Próstata/terapia , Técnicas de Cultura de Tecidos , Regulador Transcricional ERG/metabolismo , Homeobox 1 de Ligação a E-box em Dedo de Zinco/metabolismoRESUMO
Summary: Simultaneous recordings of myocytes contractility and their cytoplasmic calcium concentration allow powerful studies, particularly on heart failure and other cardiac dysfunctions. Such studies require dedicated and expensive experimental devices that are difficult to use. Thus we propose SarConfoCal, the first and only software to simultaneously analyse both cytoplasmic calcium variations (from fluorescence signal) and myocytes contractility (from sarcomere length measurement) on laser scanning confocal microscopy images. SarConfoCal is easy to set up and use, especially by people without programming skills. Availability and implementation: The software is freely distributed under the GNU General Public License. Download and setup instructions are available at http://pccv.univ-tours.fr/ImageJ/SarConfoCal . It is provided as a toolset for ImageJ (the open-source program for image analysis provided by the National Institutes of Health). SarConfoCal has been tested under Windows, Mac and Linux operating systems. Contact: come.pasqualin@univ-tours.fr. Supplementary information: Supplementary data are available at Bioinformatics online.
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Cálcio/análise , Microscopia Confocal/métodos , Células Musculares/ultraestrutura , Sarcômeros/ultraestrutura , Software , Animais , Humanos , Células Musculares/química , Sarcômeros/químicaRESUMO
Accurate measurement of cardiomyocyte contraction is a critical issue for scientists working on cardiac physiology and physiopathology of diseases implying contraction impairment. Cardiomyocytes contraction can be quantified by measuring sarcomere length, but few tools are available for this, and none is freely distributed. We developed a plug-in (SarcOptiM) for the ImageJ/Fiji image analysis platform developed by the National Institutes of Health. SarcOptiM computes sarcomere length via fast Fourier transform analysis of video frames captured or displayed in ImageJ and thus is not tied to a dedicated video camera. It can work in real time or offline, the latter overcoming rotating motion or displacement-related artifacts. SarcOptiM includes a simulator and video generator of cardiomyocyte contraction. Acquisition parameters, such as pixel size and camera frame rate, were tested with both experimental recordings of rat ventricular cardiomyocytes and synthetic videos. It is freely distributed, and its source code is available. It works under Windows, Mac, or Linux operating systems. The camera speed is the limiting factor, since the algorithm can compute online sarcomere shortening at frame rates >10 kHz. In conclusion, SarcOptiM is a free and validated user-friendly tool for studying cardiomyocyte contraction in all species, including human.
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Processamento de Imagem Assistida por Computador/métodos , Contração Miocárdica/fisiologia , Miócitos Cardíacos/fisiologia , Sarcômeros/fisiologia , Algoritmos , Animais , Análise de Fourier , Ratos , SoftwareRESUMO
The transverse tubule system in mammalian striated muscle is highly organized and contributes to optimal and homogeneous contraction. Diverse pathologies such as heart failure and atrial fibrillation include disorganization of t-tubules and contractile dysfunction. Few tools are available for the quantification of the organization of the t-tubule system. We developed a plugin for the ImageJ/Fiji image analysis platform developed by the National Institutes of Health. This plugin (TTorg) analyzes raw confocal microscopy images. Analysis options include the whole image, specific regions of the image (cropping), and z-axis analysis of the same image. Batch analysis of a series of images with identical criteria is also one of the options. There is no need to either reorientate any specimen to the horizontal or to do a thresholding of the image to perform analysis. TTorg includes a synthetic "myocyte-like" image generator to test the plugin's efficiency in the user's own experimental conditions. This plugin was validated on synthetic images for different simulated cell characteristics and acquisition parameters. TTorg was able to detect significant differences between the organization of the t-tubule systems in experimental data of mouse ventricular myocytes isolated from wild-type and dystrophin-deficient mice. TTorg is freely distributed, and its source code is available. It provides a reliable, easy-to-use, automatic, and unbiased measurement of t-tubule organization in a wide variety of experimental conditions.
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Algoritmos , Análise de Fourier , Miócitos Cardíacos/ultraestrutura , Software , Animais , Processamento de Imagem Assistida por Computador/métodos , Camundongos , Camundongos Knockout , Microscopia Confocal/métodos , Músculo Estriado/ultraestruturaRESUMO
INTRODUCTION: Ectopic activity arising from pulmonary veins (PV) plays a prominent role in the onset of atrial fibrillation in humans. Rat PV cardiac muscle cells have a lower resting membrane potential (RMP) than the left atria (LA) and presents in the presence of norepinephrine an automatic activity, which occurs in bursts. This study investigated the role of Na channels upon the RMP and the catecholaminergic automatic activity (CAA) in PV cardiac muscle. METHODS AND RESULTS: RMP and CAA experiments were performed in male Wistar rat PV. Whole-cell INa was recorded in isolated PV and LA cardiomyocytes. PV has a higher tetrodotoxin (TTX)-sensitive basal Na(+) permeability than the LA, due to a â¼ 5 mV more negative Na window current in the former tissue. TTX, quinidine, and ranolazine (1 to 10 µM each) decreased CAA incidence and arrhythmias by increasing burst intervals because of a reduction of the slope of slow depolarization between bursts. TTX and ranolazine also reduced burst duration. At 1 Hz, 10 µM quinidine, ranolazine, and TTX inhibited peak INa by 33%, 28%, and 98%, respectively. Each reduced the Na window current. There was no evidence for a TTX- or ranolazine-sensitive late Na current. CONCLUSION: Na channels confer a TTX-sensitive basal Na(+) permeability to rat PV cardiac muscle cells and contribute to the slope of slow depolarization between bursts of CAA. Na channel blockers act mostly via reduction of the Na window current. Ranolazine also has an anti-α1 adrenergic effect, which contributed to its antiarrhythmic effect.
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Catecolaminas/metabolismo , Permeabilidade da Membrana Celular/fisiologia , Veias Pulmonares/metabolismo , Sódio/metabolismo , Tetrodotoxina/farmacologia , Animais , Permeabilidade da Membrana Celular/efeitos dos fármacos , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Técnicas de Cultura de Órgãos , Veias Pulmonares/efeitos dos fármacos , Ratos , Ratos Wistar , Canais de Sódio/metabolismoRESUMO
Heart failure is characterized by a great number of metabolic and histological defects, however, previous studies did not provide strong evidence of a correlation between the antioxidant status of myocardial tissue itself and cardiac function. The goal of our study was to assess, in patients with heart failure consecutive to dilated cardiomyopathy (DCM), alterations in norepinephrine (NE), lipid peroxidation (malonedialdehyde: MDA) and iron levels in different parts of the myocardium and aorta, in relation to functional parameters. Biopsied heart samples were obtained from 12 DCM patients and from 4 brain-dead organ donors (Controls). The left ventricular ejection fraction (LVEF) was reduced to 19.1±2.6% in DCM. For all patients, the distribution of NE in the atria, ventricles and vessels was different, but NE content in control hearts was systematically higher than in cardiomyopathy patients. MDA levels tended to be higher in the different samples from the DCM group in comparison with the values obtained in the C group; the values were significantly decreased (p<0.05) in endocardium and the aortic samples. In the right atrium there was a significant correlation between NE content and LVEF and between MDA and iron concentrations. These findings could give further insights into the relationship between iron metabolism disturbances and the severity of cardiovascular diseases.
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Aorta/metabolismo , Cardiomiopatia Dilatada/metabolismo , Endocárdio/metabolismo , Átrios do Coração/metabolismo , Insuficiência Cardíaca/metabolismo , Ventrículos do Coração/metabolismo , Miocárdio/metabolismo , Adolescente , Adulto , Aorta/patologia , Aorta/fisiopatologia , Biópsia , Cardiomiopatia Dilatada/patologia , Cardiomiopatia Dilatada/fisiopatologia , Endocárdio/patologia , Endocárdio/fisiopatologia , Feminino , Átrios do Coração/patologia , Átrios do Coração/fisiopatologia , Insuficiência Cardíaca/patologia , Insuficiência Cardíaca/fisiopatologia , Ventrículos do Coração/patologia , Ventrículos do Coração/fisiopatologia , Humanos , Ferro/análise , Peroxidação de Lipídeos , Masculino , Malondialdeído/análise , Pessoa de Meia-Idade , Miocárdio/patologia , Norepinefrina/análise , Estresse Oxidativo , Volume SistólicoRESUMO
Myocardial ischemia-reperfusion injury is associated with an imbalance between the formation and the scavenging of reactive oxygen species. In this context, the protective role of the antioxidant metallothionein, a thiol-rich protein that is induced in different organs in response to heavy metals and oxidative conditions, has mainly been investigated in metallothionein-knockout mice or metallothionein-overexpressing mice. The aim of this study was to evaluate whether the administration of cadmium has a protective effect against cardiac ischemia-reperfusion injury and whether this is associated with induction of in vivo cardiac metallothionein. Forty-eight hours after an injection of 0, 1, or 2 mg/kg cadmium, isolated perfused rat hearts were submitted to 30 min of total global ischemia and 30 min of reperfusion. The ischemia-reperfusion sequence was associated with a significant decrease in cardiac metallothionein levels. Pretreatment with cadmium at a dose of 2 mg/kg (i) prevented this decrease and (ii) improved the postischemic recuperation of the coronary flow, the ventricular developed pressure, and therefore, the global postischemic functional recovery. These results showed that pretreatment of rats with 2 mg/kg cadmium induced cardioprotection against ischemia-reperfusion injuries, perhaps through an in vivo metallothionein induction that may be related to a metal activation of antioxidant systems.
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Cloreto de Cádmio/administração & dosagem , Cardiotônicos/administração & dosagem , Metalotioneína/biossíntese , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Animais , Cloreto de Cádmio/uso terapêutico , Cardiotônicos/uso terapêutico , Radicais Livres/antagonistas & inibidores , Radicais Livres/toxicidade , Técnicas In Vitro , Masculino , Metalotioneína/fisiologia , Traumatismo por Reperfusão Miocárdica/metabolismo , Perfusão/métodos , Ratos , Ratos WistarRESUMO
Ectopic activity in cardiac muscle within pulmonary veins (PVs) is associated with the onset and the maintenance of atrial fibrillation in humans. The mechanism underlying this ectopic activity is unknown. Here we investigate automatic activity generated by catecholaminergic stimulation in the rat PV. Intracellular microelectrodes were used to record electrical activity in isolated strips of rat PV and left atrium (LA). The resting cardiac muscle membrane potential was lower in PV [-70 +/- 1 (SE) mV, n = 8] than in LA (-85 +/- 1 mV, n = 8). No spontaneous activity was recorded in PV or LA under basal conditions. Norepinephrine (10(-5) M) induced first a hyperpolarization (-8 +/- 1 mV in PV, -3 +/- 1 mV in LA, n = 8 for both) then a slowly developing depolarization (+21 +/- 2 mV after 15 min in PV, +1 +/- 2 mV in LA) of the resting membrane potential. Automatic activity occurred only in PV; it was triggered at approximately -50 mV, and it occurred as repetitive bursts of slow action potentials. The diastolic membrane potential increased during a burst and slowly depolarized between bursts. Automatic activity in the PV was blocked by either atenolol or prazosine, and it could be generated with a mixture of cirazoline and isoprenaline. In both tissues, cirazoline (10(-6) M) induced a depolarization (+37 +/- 2 mV in PV, n = 5; +5 +/- 1 mV in LA, n = 5), and isoprenaline (10(-7) M) evoked a hyperpolarization (-11 +/- 3 mV in PV, n = 7; -3 +/- 1 mV in LA, n = 6). The differences in membrane potential and reaction to adrenergic stimulation lead to automatic electrical activity occurring specifically in cardiac muscle in the PV.
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Catecolaminas/fisiologia , Coração/fisiologia , Veias Pulmonares/fisiologia , Agonistas Adrenérgicos/farmacologia , Antagonistas Adrenérgicos/farmacologia , Animais , Eletrofisiologia , Átrios do Coração , Técnicas In Vitro , Masculino , Potenciais da Membrana/efeitos dos fármacos , Microeletrodos , Miocárdio , Ratos , Ratos WistarRESUMO
The study was undertaken to assess the hemodynamic effects induced by a single dose of the phosphodiesterase 4 (PDE4) inhibitor, CI-1044, which is known to cause mesenteric vascular alterations in rats. In the present study, an administration of 160 mg/kg of CI-1044 caused perivascular and interstitial inflammation, with infiltrates of admixed neutrophils and macrophages but without evidence of vascular necrosis (ileum, 15/20 rats; duodenum + jejunum, 7/20 rats). Four hours after administration, blood pressure was decreased (- 13%). A fluorescent microsphere technique demonstrated that, in these conditions, cardiac output was doubled (+ 100%) and total peripheral resistance was decreased (- 54%). The largest increases in blood flow were measured in the duodenum (+ 101%), in the jejunum (+ 110%), and in the ileum (+ 192%). Therefore, the mesentery was the most sensitive organ affected by the drug and, within this area, parts with the highest incidence of vascular alteration were those which had shown the highest increase in flow. In addition, isolated precontracted mesenteric resistance arteries dissected from untreated animals were fully relaxed when incubated with increasing concentrations of CI-1044 up to 2.5 x 10(-5)M. At this latter concentration, contractile abilities and sensitivities to the physiological agonist noradrenaline (NA) and to the thromboxane analogue U46619 were significantly attenuated (- 28 and - 27%, respectively). This effect could lead to a decreased response to NA and possibly to other agonists in vivo consistent with the vasodilation observed with the microsphere technique. These data provide evidence that the PDE4 inhibitor CI-1044 induces changes of vascular tone that could lead to histological alterations in the mesenteric area.
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Azepinas/farmacologia , Inflamação/metabolismo , Artérias Mesentéricas/efeitos dos fármacos , Niacinamida/análogos & derivados , Inibidores da Fosfodiesterase 4 , Circulação Esplâncnica/efeitos dos fármacos , Ácido 15-Hidroxi-11 alfa,9 alfa-(epoximetano)prosta-5,13-dienoico/metabolismo , Análise de Variância , Animais , Azepinas/administração & dosagem , Pressão Sanguínea/efeitos dos fármacos , Débito Cardíaco/efeitos dos fármacos , Duodeno/efeitos dos fármacos , Duodeno/metabolismo , Coração/efeitos dos fármacos , Coração/fisiologia , Hemodinâmica/efeitos dos fármacos , Íleo/efeitos dos fármacos , Íleo/metabolismo , Jejuno/efeitos dos fármacos , Jejuno/metabolismo , Masculino , Artérias Mesentéricas/metabolismo , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Necrose/metabolismo , Niacinamida/administração & dosagem , Niacinamida/farmacologia , Norepinefrina/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
BACKGROUND: Regional alterations in norepinephrine (NE) and lipid peroxidation in the myocardium of patients with heart failure is not well known. This study was designed to investigate regional myocardial NE levels and lipid peroxidation index and their relationships with the functional parameters in two pathologic conditions: dilated cardiomyopathy (DCM) and ischemic cardiomyopathy (ICM). METHODS: Biopsied heart samples were obtained from 13 DCM and 10 ICM patients (orthotopic cardiac transplantation). Tissue NE was assayed by high-pressure liquid chromatography with electrochemical detection. Tissue lipid peroxidation (malondialdehyde, MDA) was evaluated by the thiobarbituric acid (TBA) reaction. RESULTS: Non-failing hearts (controls, n = 4) were included in this study for comparison. Left ventricular dysfunction was present at rest with a mean left ventricular ejection fraction (LVEF) of 19.1 +/- 2.6% for DCM patients and 17.4 +/- 2.0% for ICM patients. The amount of NE in control hearts was significantly lower (p < 0.05) than in DCM or ICM hearts. For all patients, there were several differences in distribution of NE among the sub-divisions of the atria and ventricles studied. NE content was significantly higher in the right atria than in the left atria or ventricles. A significant correlation between LVEF and NE concentrations was observed in the left septum of ICM and DCM patients and in the left ventricle of the ICM group. In DCM and ICM patients, some parts of the left ventricle showed higher levels of lipid peroxides compared with controls. MDA levels in patients with DCM varied little from one region to another, whereas in ICM patients there was considerable variation. CONCLUSIONS: This study is the first demonstration of a correlation between the values of pre-operative LVEF and cardiac NE concentrations in specific parts of the myocardium. This effect could not be generalized to the entire heart. The pattern of myocardial MDA distribution did not follow that of the NE distribution.
Assuntos
Cardiomiopatia Dilatada/metabolismo , Insuficiência Cardíaca/metabolismo , Isquemia Miocárdica/metabolismo , Miocárdio/química , Norepinefrina/análise , Biópsia , Cardiomiopatia Dilatada/complicações , Cardiomiopatia Dilatada/patologia , Feminino , Insuficiência Cardíaca/patologia , Humanos , Peroxidação de Lipídeos , Masculino , Pessoa de Meia-Idade , Isquemia Miocárdica/complicações , Isquemia Miocárdica/patologia , Índice de Gravidade de DoençaRESUMO
The aim of this study was to investigate the in vitro vasomotor properties of rat extra-and intralobar pulmonary veins (PVs) related to their localization and to assess the modulatory role of endothelium on these properties. Segments from PVs were mounted in small vessel myograph and stretched at various diameters (D(10), D(20), D(30)) corresponding to intraluminal pressures of 10, 20 or 30 mmHg. At D(10) or D(20), contractile responses to phenylephrine, U46619 and angiotensin II of distal intralobar part of PVs were smaller compared with those of proximal extralobar part, but no longer different when distal part was stretched at D(30). When submitted to an NO donor, sodium nitroprusside, distal part of PV relaxed more strongly when stretched at D(30) compared with D(10). Acetylcholine and bradykinin were devoid of relaxing effect on distal parts stretched at D(10), but in contrast to acetylcholine, bradykinin slightly relaxed preparations stretched at D(30). Isoprenaline strongly relaxed PVs ( approximately 80% of initial precontraction), with the distal part exhibiting a higher sensitivity to the agonist compared with the proximal part. This relaxation was also observed with salbutamol and suppressed with ICI 118551, which is in favour of the involvement of beta(2)-adrenoceptors in this effect. Preincubation of the preparations with N(G)-nitro-l-arginine methyl ester (10(-4) m) and indomethacin (10(-5) m) did not modify the contractile responses to U46619, nor the relaxing response to isoprenaline, which support that endothelium does not appear to play a significant modulatory role in these responses. Histological and electron microscopical examinations of proximal and distal sections of the same vein show that the layers of smooth muscle cells and cardiomyocytes were thicker in the proximal compared with the distal part. This study shows that, because of morphological heterogeneity of the PVs, the site of dissection and the initial condition of tension can play a significant role upon the sensitivity and the magnitude of the responses to both contractile and relaxing agonists.
Assuntos
Veias Pulmonares/fisiologia , Vasoconstrição/fisiologia , Vasodilatação/fisiologia , Ácido 15-Hidroxi-11 alfa,9 alfa-(epoximetano)prosta-5,13-dienoico/farmacologia , Acetilcolina/farmacologia , Agonistas de Receptores Adrenérgicos beta 2 , Antagonistas de Receptores Adrenérgicos beta 2 , Agonistas Adrenérgicos beta/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Albuterol/farmacologia , Angiotensina II/farmacologia , Animais , Bradicinina/farmacologia , Brônquios , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/fisiologia , Átrios do Coração , Técnicas In Vitro , Isoproterenol/farmacologia , Masculino , Nitroprussiato/farmacologia , Fenilefrina/farmacologia , Propanolaminas/farmacologia , Veias Pulmonares/anatomia & histologia , Veias Pulmonares/efeitos dos fármacos , Ratos , Ratos Wistar , Receptores Adrenérgicos beta 2/fisiologia , Vasoconstrição/efeitos dos fármacos , Vasoconstritores/farmacologia , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologiaRESUMO
Metallothionein (MT), induced in different organs in response to heavy metals and oxidative conditions, exerts antioxidant properties and thus could be implicated in cardiovascular physiopathology. The aim of this study was to investigate the capacity of cadmium (Cd) and isoproterenol to induce in vivo MT not only in rat liver and kidneys but also in heart and aorta. Tissue MT levels, catalase (CAT) and glutathione peroxidase (GPX) activities were assayed at different times after Cd or isoproterenol injection. Cd induced a dose-dependent induction of MT with a higher response in the liver than in the kidney, aorta and heart. The hepatic increase was early (12 h) and maintained (72 h), whereas the elevation was maximal around 48 h for the other organs. Isoproterenol induced a transient (12 h) hepatic and a biphasic (12 and 36 h) renal and cardiac increase. CAT activity was decreased in the liver and increased in the heart with the higher Cd doses. Isoproterenol increased the cardiac GPX activity. In conclusion, the results demonstrate that MT can be induced in rat liver and kidneys but also in heart after a Cd or isoproterenol injection. This enhancement of cardiac and vascular MT levels could be used to study the potential protective effect of MT in cardiovascular diseases.