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1.
J Immigr Minor Health ; 22(4): 691-700, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32072377

RESUMO

Latinas face barriers to contraceptive and preconception care. Using a Reproductive Health Self-Assessment Tool (RH-SAT) before primary care visits may help overcome these barriers. Twenty Spanish-speaking women at a Federally Qualified Health Center in Chicago received the RH-SAT before their visit then completed a phone interview about their perceptions of the RH-SAT. Transcripts were thematically analyzed using a modified grounded theoretical approach. All participants self-reported Hispanic/Latina ethnicity, either of Mexican (N = 19) or Puerto Rican (N = 1) origin. Participants (1) believed the RH-SAT was easy to use and its content was useful for women with a variety of reproductive goals; (2) felt it provided new information about preparing for pregnancy and contraception; (3) were prompted by the RH-SAT to self-reflect and ask questions not previously considered; and (4) felt it could help overcome barriers some women experience in discussing reproductive health. Participants felt the RH-SAT provided new information and would prompt them to discuss contraception and/or preparing for pregnancy with their clinician. This tool has the potential to facilitate patient-clinician discussion of reproductive health in primary care and overcome barriers experienced by some Spanish-speaking women.


Assuntos
Hispânico ou Latino/psicologia , Idioma , Atenção Primária à Saúde/organização & administração , Serviços de Saúde Reprodutiva/organização & administração , Provedores de Redes de Segurança/organização & administração , Inquéritos e Questionários/normas , Adolescente , Adulto , Chicago/epidemiologia , Anticoncepção/métodos , Competência Cultural , Serviços de Planejamento Familiar/organização & administração , Feminino , Humanos , México/etnologia , Pessoa de Meia-Idade , Percepção , Porto Rico/etnologia , Autoavaliação (Psicologia) , Adulto Jovem
2.
J Mol Cell Cardiol ; 120: 74-83, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29807024

RESUMO

Right heart failure is the major cause of death in Pulmonary Artery Hypertension (PAH) patients but is not a current, specific therapeutic target. Pre-clinical studies have shown that adrenoceptor blockade can improve cardiac function but the mechanisms of action within right ventricular (RV) myocytes are unknown. We tested whether the ß1-adrenoceptor blocker metoprolol could improve RV myocyte function in an animal model of PAH, by attenuating adverse excitation-contraction coupling remodeling. PAH with RV failure was induced in rats by monocrotaline injection. When PAH was established, animals were given 10 mg/kg/day metoprolol (MCT + BB) or vehicle (MCT). The median time to the onset of heart failure signs was delayed from 23 days (MCT), to 31 days (MCT + BB). At 23 ±â€¯1 days post-injection, MCT + BB showed improved in vivo cardiac function, measured by echocardiography. RV hypertrophy was reduced despite persistent elevated afterload. RV myocyte contractility during field stimulation was improved at higher pacing frequencies in MCT + BB. Preserved t-tubule structure, more uniform evoked Ca2+ release, increased SERCA2a expression and faster ventricular repolarization (measured in vivo by telemetry) may account for the improved contractile function. Sarcoplasmic reticulum Ca2+ overload was prevented in MCT + BB myocytes resulting in fewer spontaneous Ca2+ waves, with a lower pro-arrhythmic potential. Our novel finding of attenuation of defects in excitation contraction coupling by ß1-adrenoceptor blockade with delays in the onset of HF, identifies the RV as a promising therapeutic target in PAH. Moreover, our data suggest existing therapies for left ventricular failure may also be beneficial in PAH induced RV failure.


Assuntos
Antagonistas de Receptores Adrenérgicos beta 1/uso terapêutico , Cálcio/metabolismo , Hipertensão Pulmonar/tratamento farmacológico , Metoprolol/uso terapêutico , Miócitos Cardíacos/metabolismo , Artéria Pulmonar/fisiopatologia , Disfunção Ventricular Direita/tratamento farmacológico , Antagonistas de Receptores Adrenérgicos beta 1/administração & dosagem , Análise de Variância , Animais , Modelos Animais de Doenças , Ecocardiografia , Eletrocardiografia , Insuficiência Cardíaca/metabolismo , Hipertensão Pulmonar/diagnóstico por imagem , Hipertrofia Ventricular Direita/tratamento farmacológico , Masculino , Metoprolol/administração & dosagem , Ratos , Ratos Wistar , Volume Sistólico/efeitos dos fármacos , Disfunção Ventricular Direita/diagnóstico por imagem
3.
Clin Exp Pharmacol Physiol ; 45(4): 384-389, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29193283

RESUMO

Passive properties of the myocardium influence diastolic filling and cardiac output. In heart failure, changes in contributors to the passive properties of the ventricle, such as titin and collagen, and loss of the metabolic enzyme creatine kinase, increase resistance to filling resulting in diastolic dysfunction. Pulmonary artery hypertension (PAH) arises from interactions between the pulmonary vasculature and the right ventricle (RV) which ultimately leads to RV failure. Beta1-adrenergic receptor blockers (BB) act on the myocardium and are beneficial in left heart failure but are not used in PAH. We investigated whether BB improved survival and RV function in a rat model of PAH. Rats were injected with monocrotaline (60 mg/kg) to induce PAH and RV failure, or saline as controls (CON). When PAH was established, rats were treated with metoprolol (10 mg/kg per day) (MCT+BB) or vehicle (sucrose) (MCT); CON were treated with vehicle. In vivo measurement of RV compliance using pressure-volume catheter, indicated diastolic dysfunction in the RV of MCT rats was improved with BB treatment. Expression of creatine kinase protein and mRNA was lower in MCT rats compared to CON, with a trend for reversion by BB treatment. Isolated CON RV myocytes had a positive contraction response to faster pacing, whereas it was negative in MCT. MCT+BB cells had an intermediate response, indicating improved ability to respond to increased demand. BB improved diastolic function, partially restored metabolic enzymes and augmented contractility in PAH. These data support the hypothesis that BB may be beneficial in PAH by supporting RV function.


Assuntos
Antagonistas Adrenérgicos beta/farmacologia , Creatina Quinase/metabolismo , Diástole/efeitos dos fármacos , Hipertensão Pulmonar/tratamento farmacológico , Hipertensão Pulmonar/fisiopatologia , Antagonistas Adrenérgicos beta/uso terapêutico , Animais , Humanos , Hipertensão Pulmonar/enzimologia
4.
Womens Health Issues ; 27(3): 322-328, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-27931733

RESUMO

INTRODUCTION: Given the potential benefits of preventive reproductive health care for both women and children, it is important that clinicians routinely offer preconception and contraceptive counseling in ways that are responsive to patients' wishes. The goal of this study is to gain knowledge about the components of preventive reproductive health care that patients at Federally Qualified Health Centers value, and to elicit patient perspectives on how best to deliver this care. METHODS: We conducted three focus groups with African American women (n = 21) at two Federally Qualified Health Centers in Chicago. The groups were facilitated using an open-ended, semistructured interview guide. We asked women to reflect on past experiences, advice they would give their teenage daughters, and how to design an ideal clinic. All groups were recorded and transcribed verbatim. Transcripts were coded and analyzed using an inductive approach with ATLAS.ti software. RESULTS: Although participants wanted comprehensive information about sex and pregnancy, they reported receiving no information at all, or many negative messages. The idea of timing and spacing pregnancies was generally embraced by participants. They described an ideal clinic as having a patient population diverse in income, trusting relationships with providers, comprehensive services, and educational opportunities. CONCLUSIONS: The women in our study expressed a desire for more information and comprehensive care in the setting of an equitable clinic where they feel respected as individuals. Our findings support the idea behind the patient-centered medical home and challenge prior literature, which suggests the concept of pregnancy planning does not resonate with low-income African American women.


Assuntos
Negro ou Afro-Americano , Centros Comunitários de Saúde/organização & administração , Serviços de Planejamento Familiar/organização & administração , Disparidades em Assistência à Saúde/etnologia , Cuidado Pré-Concepcional/organização & administração , Qualidade da Assistência à Saúde , Serviços de Saúde Reprodutiva/organização & administração , Saúde Reprodutiva/etnologia , Adolescente , Adulto , Atitude do Pessoal de Saúde , Chicago , Feminino , Grupos Focais , Humanos , Entrevistas como Assunto , Pessoa de Meia-Idade , Gravidez , Pesquisa Qualitativa , Adulto Jovem
5.
J Mol Cell Cardiol ; 86: 1-8, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26116865

RESUMO

Our objective was to investigate the role of creatine kinase in the contractile dysfunction of right ventricular failure caused by pulmonary artery hypertension. Pulmonary artery hypertension and right ventricular failure were induced in rats by monocrotaline and compared to saline-injected control animals. In vivo right ventricular diastolic pressure-volume relationships were measured in anesthetized animals; diastolic force-length relationships in single enzymatically dissociated myocytes and myocardial creatine kinase levels by Western blot. We observed diastolic dysfunction in right ventricular failure indicated by significantly steeper diastolic pressure-volume relationships in vivo and diastolic force-length relationships in single myocytes. There was a significant reduction in creatine kinase protein expression in failing right ventricle. Dysfunction also manifested as a shorter diastolic sarcomere length in failing myocytes. This was associated with a Ca(2+)-independent mechanism that was sensitive to cross-bridge cycling inhibition. In saponin-skinned failing myocytes, addition of exogenous creatine kinase significantly lengthened sarcomeres, while in intact healthy myocytes, inhibition of creatine kinase significantly shortened sarcomeres. Creatine kinase inhibition also changed the relatively flat contraction amplitude-stimulation frequency relationship of healthy myocytes into a steeply negative, failing phenotype. Decreased creatine kinase expression leads to diastolic dysfunction. We propose that this is via local reduction in ATP:ADP ratio and thus to Ca(2+)-independent force production and diastolic sarcomere shortening. Creatine kinase inhibition also mimics a definitive characteristic of heart failure, the inability to respond to increased demand. Novel therapies for pulmonary artery hypertension are needed. Our data suggest that cardiac energetics would be a potential ventricular therapeutic target.


Assuntos
Creatina Quinase/metabolismo , Insuficiência Cardíaca/enzimologia , Hipertensão Pulmonar/enzimologia , Disfunção Ventricular Direita/enzimologia , Trifosfato de Adenosina/metabolismo , Animais , Cálcio/metabolismo , Creatina Quinase/biossíntese , Diástole , Insuficiência Cardíaca/patologia , Humanos , Hipertensão Pulmonar/patologia , Miocárdio/enzimologia , Miocárdio/patologia , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/patologia , Artéria Pulmonar/enzimologia , Artéria Pulmonar/patologia , Ratos , Sarcômeros/enzimologia , Sarcômeros/patologia , Disfunção Ventricular Direita/patologia
6.
Prog Biophys Mol Biol ; 115(2-3): 162-72, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25016242

RESUMO

We demonstrate the synergistic benefits of using multiple technologies to investigate complex multi-scale biological responses. The combination of reductionist and integrative methodologies can reveal novel insights into mechanisms of action by tracking changes of in vivo phenomena to alterations in protein activity (or vice versa). We have applied this approach to electrical and mechanical remodelling in right ventricular failure caused by monocrotaline-induced pulmonary artery hypertension in rats. We show arrhythmogenic T-wave alternans in the ECG of conscious heart failure animals. Optical mapping of isolated hearts revealed discordant action potential duration (APD) alternans. Potential causes of the arrhythmic substrate; structural remodelling and/or steep APD restitution and dispersion were observed, with specific remodelling of the Right Ventricular Outflow Tract. At the myocyte level, [Ca(2+)]i transient alternans were observed together with decreased activity, gene and protein expression of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA). Computer simulations of the electrical and structural remodelling suggest both contribute to a less stable substrate. Echocardiography was used to estimate increased wall stress in failure, in vivo. Stretch of intact and skinned single myocytes revealed no effect on the Frank-Starling mechanism in failing myocytes. In isolated hearts acute stretch-induced arrhythmias occurred in all preparations. Significant shortening of the early APD was seen in control but not failing hearts. These observations may be linked to changes in the gene expression of candidate mechanosensitive ion channels (MSCs) TREK-1 and TRPC1/6. Computer simulations incorporating MSCs and changes in ion channels with failure, based on altered gene expression, largely reproduced experimental observations.


Assuntos
Arritmias Cardíacas/fisiopatologia , Acoplamento Excitação-Contração , Sistema de Condução Cardíaco/fisiopatologia , Hipertensão Pulmonar/fisiopatologia , Mecanotransdução Celular , Disfunção Ventricular Direita/fisiopatologia , Animais , Arritmias Cardíacas/induzido quimicamente , Módulo de Elasticidade , Sistema de Condução Cardíaco/efeitos dos fármacos , Hipertensão Pulmonar/induzido quimicamente , Ativação do Canal Iônico , Canais Iônicos/metabolismo , Monocrotalina , Estimulação Física/métodos , Ratos , Ratos Wistar , Estresse Mecânico , Biologia de Sistemas/métodos , Disfunção Ventricular Direita/induzido quimicamente , Remodelação Ventricular
7.
J Mol Cell Cardiol ; 56: 91-6, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23261965

RESUMO

Microtubules are components of the cardiac cytoskeleton that can proliferate in response to pressure-overload in animal and human heart failure. We wished to test whether there was a proliferation of the microtubule cytoskeleton in the right ventricle of rats with pulmonary hypertension induced by monocrotaline (MCT) and whether this contributed to contractile dysfunction. Male Wistar rats were injected with 60mg/kg of MCT in saline or an equivalent volume of saline (CON). MCT produced clinical signs of heart failure within 4weeks of injection. Expression of right ventricular mRNA for α-tubulin was measured by real-time reverse transcription polymerase chain reaction. Free and polymerised fractions of ß-tubulin protein were assessed using Western blot analysis and immunofluorescence microscopy was used to assess tyrosinated and acetylated (stabilized) microtubules. Right ventricular myocyte contraction was measured in response to the microtubule de-polymeriser colchicine (10µmol/l for at least 1h). Compared to CON, in MCT right ventricles there was a small but statistically significant increase in the expression of mRNA for α-tubulin (P<0.001); total (P<0.05) and polymerised fraction (P<0.01) of ß-tubulin protein and level of acetylated tubulin (P<0.01). However colchicine treatment did not increase the contraction of MCT myocytes (P>0.05) or affect their response to increased stimulation frequency. Our observations support the hypothesis that microtubule proliferation is a common response to pulmonary hypertension in failing right ventricles but suggest that the effect this has on contraction depends upon the specific experimental or clinical conditions that prevail and the subsequent level of microtubule proliferation.


Assuntos
Ventrículos do Coração/patologia , Hipertensão Pulmonar/metabolismo , Microtúbulos/metabolismo , Miócitos Cardíacos/metabolismo , Animais , Células Cultivadas , Colchicina/farmacologia , Hipertensão Pulmonar/induzido quimicamente , Hipertensão Pulmonar/patologia , Masculino , Microtúbulos/patologia , Monocrotalina , Tamanho do Órgão , Multimerização Proteica , Processamento de Proteína Pós-Traducional , Ratos , Ratos Wistar , Sarcômeros/metabolismo , Tubulina (Proteína)/metabolismo , Moduladores de Tubulina/farmacologia
8.
Am J Physiol Heart Circ Physiol ; 302(11): H2381-95, 2012 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-22427523

RESUMO

Pulmonary hypertension provokes right heart failure and arrhythmias. Better understanding of the mechanisms underlying these arrhythmias is needed to facilitate new therapeutic approaches for the hypertensive, failing right ventricle (RV). The aim of our study was to identify the mechanisms generating arrhythmias in a model of RV failure induced by pulmonary hypertension. Rats were injected with monocrotaline to induce either RV hypertrophy or failure or with saline (control). ECGs were measured in conscious, unrestrained animals by telemetry. In isolated hearts, electrical activity was measured by optical mapping and myofiber orientation by diffusion tensor-MRI. Sarcoplasmic reticular Ca(2+) handling was studied in single myocytes. Compared with control animals, the T-wave of the ECG was prolonged and in three of seven heart failure animals, prominent T-wave alternans occurred. Discordant action potential (AP) alternans occurred in isolated failing hearts and Ca(2+) transient alternans in failing myocytes. In failing hearts, AP duration and dispersion were increased; conduction velocity and AP restitution were steeper. The latter was intrinsic to failing single myocytes. Failing hearts had greater fiber angle disarray; this correlated with AP duration. Failing myocytes had reduced sarco(endo)plasmic reticular Ca(2+)-ATPase activity, increased sarcoplasmic reticular Ca(2+)-release fraction, and increased Ca(2+) spark leak. In hypertrophied hearts and myocytes, dysfunctional adaptation had begun, but alternans did not develop. We conclude that increased electrical and structural heterogeneity and dysfunctional sarcoplasmic reticular Ca(2+) handling increased the probability of alternans, a proarrhythmic predictor of sudden cardiac death. These mechanisms are potential therapeutic targets for the correction of arrhythmias in hypertensive, failing RVs.


Assuntos
Arritmias Cardíacas/fisiopatologia , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/fisiopatologia , Hipertensão Pulmonar/complicações , Disfunção Ventricular Direita/fisiopatologia , Potenciais de Ação/fisiologia , Animais , Cálcio/metabolismo , ATPases Transportadoras de Cálcio/metabolismo , Eletrocardiografia , Masculino , Modelos Animais , Miócitos Cardíacos/patologia , Ratos , Ratos Wistar , Retículo Sarcoplasmático/metabolismo
9.
Am J Physiol Heart Circ Physiol ; 302(2): H402-11, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22037189

RESUMO

Exercise intolerance is a cardinal symptom of right ventricular heart failure (RV HF) and skeletal muscle adaptations play a role in this limitation. We determined regional remodeling of muscle structure and mitochondrial function in a rat model of RV HF induced by monocrotaline injection (MCT; 60 mg·kg(-1); n = 11). Serial sections of the plantaris were stained for fiber type, succinate dehydrogenase (SDH) activity and capillaries. Mitochondrial function was assessed in permeabilized fibers using respirometry, and isolated complex activity by blue native gel electrophoresis (BN PAGE). All measurements were compared with saline-injected control animals (CON; n = 12). Overall fiber cross-sectional area was smaller in MCT than CON: 1,843 ± 114 vs. 2,322 ± 120 µm(2) (P = 0.009). Capillary-to-fiber ratio was lower in MCT in the oxidative plantaris region (1.65 ± 0.09 vs. 1.93 ± 0.07; P = 0.03), but not in the glycolytic region. SDH activity (P = 0.048) and maximal respiratory rate (P = 0.012) were each ∼15% lower in all fibers in MCT. ADP sensitivity was reduced in both skeletal muscle regions in MCT (P = 0.032), but normalized by rotenone. A 20% lower complex I/IV activity in MCT was confirmed by BN PAGE. MCT-treatment was associated with lower mitochondrial volume density (lower SDH activity), quality (lower complex I activity), and fewer capillaries per fiber area in oxidative skeletal muscle. These features are consistent with structural and functional remodeling of the determinants of oxygen supply potential and utilization that may contribute to exercise intolerance and reduced quality of life in patients with RV HF.


Assuntos
Insuficiência Cardíaca/fisiopatologia , Coração/fisiopatologia , Mitocôndrias/metabolismo , Músculo Esquelético/fisiopatologia , Miocárdio/metabolismo , Disfunção Ventricular Direita/fisiopatologia , Animais , Insuficiência Cardíaca/metabolismo , Masculino , Músculo Esquelético/metabolismo , Consumo de Oxigênio/fisiologia , Ratos , Ratos Wistar , Succinato Desidrogenase/metabolismo , Disfunção Ventricular Direita/metabolismo
10.
Am J Physiol Heart Circ Physiol ; 300(6): H2230-7, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21398591

RESUMO

Mechanisms associated with right ventricular (RV) hypertension and arrhythmias are less understood than those in the left ventricle (LV). The aim of our study was to investigate whether and by what mechanisms a proarrhythmic substrate exists in a rat model of RV hypertension and hypertrophy. Rats were injected with monocrotaline (MCT; 60 mg/kg) to induce pulmonary artery hypertension or with saline (CON). Myocardial levels of mRNA for genes expressing ion channels were measured by real-time RT-PCR. Monophasic action potential duration (MAPD) was recorded in isolated Langendorff-perfused hearts. MAPD restitution was measured, and arrhythmias were induced by burst stimulation. Twenty-two to twenty-six days after treatment, MCT animals had RV hypertension, hypertrophy, and decreased ejection fractions compared with CON. A greater proportion of MCT hearts developed sustained ventricular tachycardias/fibrillation (0.83 MCT vs. 0.14 CON). MAPD was prolonged in RV and less so in the LV of MCT hearts. There were decreased levels of mRNA for K(+) channels. Restitution curves of MCT RV were steeper than CON RV or either LV. Dispersion of MAPD was greater in MCT hearts and was dependent on stimulation frequency. Computer simulations based on ion channel gene expression closely predicted experimental changes in MAPD and restitution. We have identified a proarrhythmic substrate in the hearts of MCT-treated rats. We conclude that steeper RV electrical restitution and rate-dependant RV-LV action potential duration dispersion may be contributing mechanisms and be implicated in the generation of arrhythmias associated with in RV hypertension and hypertrophy.


Assuntos
Arritmias Cardíacas/fisiopatologia , Hipertensão Pulmonar/induzido quimicamente , Hipertensão Pulmonar/fisiopatologia , Hipertrofia Ventricular Direita/induzido quimicamente , Hipertrofia Ventricular Direita/fisiopatologia , Monocrotalina/efeitos adversos , Potenciais de Ação/fisiologia , Animais , Canais de Cálcio/fisiologia , Simulação por Computador , Modelos Animais de Doenças , Estimulação Elétrica , Masculino , Canais de Potássio/fisiologia , Ratos , Ratos Wistar , Volume Sistólico/fisiologia , Taquicardia Ventricular/fisiopatologia
11.
Basic Res Cardiol ; 104(6): 643-52, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19415411

RESUMO

Regular exercise can lead to electrical remodelling of the heart. The cellular mechanisms associated with these changes are not well understood, and are difficult to study in human tissue but are important given that exercise is recommended to the general population. We have investigated the role played by the transient outward K+ current (I(to)) in the changes in electrical activity seen in response to voluntary exercise training in rats. Female rats undertook 6 weeks of voluntary wheel running exercise (TRN) or were sedentary controls (SED). Monophasic action potentials (MAPs) were recorded from the surface of whole hearts. Whole cell patch clamp recordings of I(to); mRNA and protein levels of selected targets in sub-epicardial (EPI) and sub-endocardial myocardium of SED and TRN hearts were compared. In TRN rats, heart weight:body weight was significantly increased and epicardial MAPs significantly prolonged. I(to) density was reduced in TRN EPI myocytes, such that the transmural gradient of I(to) was significantly reduced (P < 0.05). Computer modelling of these changes in I(to) predicted the observed changes in action potential profile. However, transmural gradients in mRNA and protein expression for Kv4.2 or mRNA levels of the Kv4.2 regulators; KChIP2 and Irx-5 were not significantly altered by voluntary exercise. We conclude that voluntary exercise electrical remodelling is caused, at least in part, by a decrease in EPI I(to), possibly because of fewer functional channels in the membrane, which results in a fall in the transmural action potential duration gradient.


Assuntos
Potenciais de Ação/fisiologia , Coração/fisiologia , Pericárdio/fisiologia , Condicionamento Físico Animal/fisiologia , Canais de Potássio/metabolismo , Animais , Western Blotting , Simulação por Computador , Endocárdio/metabolismo , Endocárdio/fisiologia , Feminino , Coração/anatomia & histologia , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteínas Interatuantes com Canais de Kv/genética , Proteínas Interatuantes com Canais de Kv/metabolismo , Miócitos Cardíacos/fisiologia , Técnicas de Patch-Clamp , Pericárdio/anatomia & histologia , Potássio/metabolismo , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Remodelação Ventricular/fisiologia
12.
Exp Physiol ; 93(9): 1065-75, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18487315

RESUMO

Regular exercise is beneficial to cardiovascular health. We tested whether mild voluntary exercise training modifies key myocardial parameters [ventricular mass, intracellular calcium ([Ca2+]i) handling and the response to beta-adrenoceptor (beta-AR) stimulation] in a manner distinct from that reported for beneficial, intensive training and pathological hypertrophic stimuli. Female rats performed voluntary wheel-running exercise for 6-7 weeks. The mRNA expression of target proteins was measured in left ventricular tissue using real-time reverse transcriptase-polymerase chain reaction. Simultaneous measurement of cell shortening and [Ca2+]i transients were made in single left ventricular myocytes and the inotropic response to beta1- and beta2-AR stimulation was measured. Voluntary exercise training resulted in cardiac hypertrophy, the heart weight to body weight ratio being significantly greater in trained compared with sedentary animals. However, voluntary exercise caused no significant alteration in the size or time course of myocyte shortening and [Ca2+]i transients or in the mRNA levels of key proteins that regulate Ca2+ handling. The positive inotropic response to beta1-AR stimulation and the level of beta1-AR mRNA were unaltered by voluntary exercise but both mRNA levels and inotropic response to beta2-AR stimulation were significantly reduced in trained animals. The beta2-AR inotropic response was restored by exposure to pertussis toxin. We propose that in contrast to pathological stimuli and to beneficial, intense exercise training, modulation of Ca2+ handling is not a major adaptive mechanism in the response to mild voluntary exercise. In addition, and in a reversal of the situation seen in heart failure, voluntary exercise training maintains the beta1-AR response but reduces the beta2-AR response. Therefore, although voluntary exercise induces cardiac hypertrophy, there are distinct differences between its effects on key myocardial regulatory mechanisms and those of hypertrophic stimuli that eventually cause cardiac decompensation.


Assuntos
Miócitos Cardíacos/metabolismo , Condicionamento Físico Animal/fisiologia , Receptores Adrenérgicos beta 2/metabolismo , Transdução de Sinais/fisiologia , Animais , Cálcio/metabolismo , Cardiomegalia/metabolismo , Cardiotônicos/farmacologia , Feminino , Isoproterenol/farmacologia , Miócitos Cardíacos/citologia , Miócitos Cardíacos/efeitos dos fármacos , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores Adrenérgicos beta 1/metabolismo , Receptores Adrenérgicos beta 2/genética
13.
Prog Biophys Mol Biol ; 97(2-3): 268-81, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18485455

RESUMO

Mechanical stimulation has important consequences for myocardial function. However, this stimulation and the response to it, is not uniform. The right ventricle is thinner walled and operates at lower pressure than the left ventricle. Within the ventricles, differences in the orientation of myocardial fibres exist. These differences produce inhomogeneity in the stress and strain between and across the ventricles. Possibly as a result of these variations in mechanical stimulation, there are well characterised inhomogeneities in gene expression and protein function within the ventricular myocardium, for example in the transient outward K+ current and its associated Kv channels. Perhaps not surprisingly, it is becoming apparent that gradients of expression and function exist for proteins that are intimately involved in the response to mechanical stimulation in the heart, for example in the left ventricle of the rat there is a transmural gradient in mRNA and current density of the mechanosensitive two-pore domain K+ channel TREK-1 (ENDO>EPI). In healthy hearts it is assumed that these gradients are important for normal function and therefore that their disruption in diseased myocardium is involved in the dysfunction that occurs.


Assuntos
Coração/fisiologia , Mecanotransdução Celular/fisiologia , Miocárdio/metabolismo , Canais de Potássio de Domínios Poros em Tandem/fisiologia , Animais , Expressão Gênica , Ratos , Função Ventricular
14.
Eur J Pharmacol ; 512(2-3): 117-20, 2005 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-15840395

RESUMO

We measured the contractile response of left ventricular cardiac myocytes from female rats to selective beta(1)-adrenoceptor stimulation (isoprenaline, 10(-8) M and 10(-7) M in the presence of 10(-7) M ICI 118,551 a beta2-adrenoceptor inverse agonist). A heterogenic response to stimulation, inversely related to the extent of cell shortening prior to adrenergic stimulation, was observed. Challenge of cardiac myocytes with a selective beta1-antagonist, atenolol (10(-7) M), suggests the heterogenic response is not caused by basal beta1-adrenoceptor activity. Thus, basal myocyte contractility determines the response to beta1-adrenoceptor stimulation, this should be taken into account when experimental conditions are designed.


Assuntos
Miócitos Cardíacos/fisiologia , Receptores Adrenérgicos beta 1/fisiologia , Função Ventricular , Agonistas de Receptores Adrenérgicos beta 1 , Antagonistas de Receptores Adrenérgicos beta 1 , Agonistas Adrenérgicos beta/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Animais , Atenolol/farmacologia , Forma Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Feminino , Ventrículos do Coração/citologia , Ventrículos do Coração/efeitos dos fármacos , Isoproterenol/farmacologia , Modelos Lineares , Miócitos Cardíacos/citologia , Miócitos Cardíacos/efeitos dos fármacos , Propanolaminas/farmacologia , Ratos , Ratos Sprague-Dawley
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