RESUMO
Cardiac remodeling is defined as changes in shape and function of the heart in response to aggression (pressure overload). The sarcoplasmic reticulum calcium ATPase cardiac isoform 2a (SERCA2a) is a known factor that influences function. A wide spectrum of studies report a decrease in SERCA2a in heart failure, but none evaluate it's the role in early isolated diastolic dysfunction in supravalvular aortic stenosis (AoS). Our hypothesis was that SERCA2a participates in such dysfunction. Thirty-day-old male Wistar rats (60-80 g) were divided into AoS and Sham groups, which were submitted to surgery with or without aorta clipping, respectively. After 6 weeks, the animals were submitted to echocardiogram and functional analysis by isolated papillary muscle (IPM) in basal condition, hypoxia, and SERCA2a blockage with cyclopiazonic acid at calcium concentrations of 0.5, 1.5, and 2.5 mM. Western-blot analyses were used for SERCA2a and phospholamban detection. Data analysis was carried out with Student's t-test and ANOVA. AoS enhanced left atrium and E and A wave ratio, with preserved ejection fraction. Basal condition in IPM showed similar increases in developed tension (DT) and resting tension (RT) in AoS, and hypoxia was similar between groups. After cyclopiazonic acid blockage, final DT was equally decreased and RT was similar between groups, but the speed of relaxation was decreased in the AoS group. Western-blot was uniform in all evaluations. The hypothesis was confirmed, since functional parameters regarding SERCA2a were changed in the AoS group.
Assuntos
Estenose Aórtica Supravalvular/complicações , Hipertrofia Ventricular Esquerda/fisiopatologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/fisiologia , Disfunção Ventricular Esquerda/fisiopatologia , Animais , Estenose Aórtica Supravalvular/metabolismo , Proteínas de Ligação ao Cálcio/análise , Colágeno/análise , Diástole/fisiologia , Modelos Animais de Doenças , Ecocardiografia , Ventrículos do Coração/patologia , Ventrículos do Coração/fisiopatologia , Hipertrofia Ventricular Esquerda/etiologia , Hipertrofia Ventricular Esquerda/metabolismo , Hipóxia/metabolismo , Hipóxia/fisiopatologia , Indóis , Masculino , Contração Miocárdica/fisiologia , Ratos Wistar , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/análise , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Fatores de Tempo , Disfunção Ventricular Esquerda/etiologia , Disfunção Ventricular Esquerda/metabolismo , Remodelação Ventricular/fisiologiaRESUMO
Cardiac remodeling is defined as changes in shape and function of the heart in response to aggression (pressure overload). The sarcoplasmic reticulum calcium ATPase cardiac isoform 2a (SERCA2a) is a known factor that influences function. A wide spectrum of studies report a decrease in SERCA2a in heart failure, but none evaluate it's the role in early isolated diastolic dysfunction in supravalvular aortic stenosis (AoS). Our hypothesis was that SERCA2a participates in such dysfunction. Thirty-day-old male Wistar rats (60-80 g) were divided into AoS and Sham groups, which were submitted to surgery with or without aorta clipping, respectively. After 6 weeks, the animals were submitted to echocardiogram and functional analysis by isolated papillary muscle (IPM) in basal condition, hypoxia, and SERCA2a blockage with cyclopiazonic acid at calcium concentrations of 0.5, 1.5, and 2.5 mM. Western-blot analyses were used for SERCA2a and phospholamban detection. Data analysis was carried out with Student's t-test and ANOVA. AoS enhanced left atrium and E and A wave ratio, with preserved ejection fraction. Basal condition in IPM showed similar increases in developed tension (DT) and resting tension (RT) in AoS, and hypoxia was similar between groups. After cyclopiazonic acid blockage, final DT was equally decreased and RT was similar between groups, but the speed of relaxation was decreased in the AoS group. Western-blot was uniform in all evaluations. The hypothesis was confirmed, since functional parameters regarding SERCA2a were changed in the AoS group.
Assuntos
Animais , Masculino , Estenose Aórtica Supravalvular/complicações , Hipertrofia Ventricular Esquerda/fisiopatologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/fisiologia , Disfunção Ventricular Esquerda/fisiopatologia , Estenose Aórtica Supravalvular/metabolismo , Proteínas de Ligação ao Cálcio/análise , Colágeno/análise , Diástole/fisiologia , Modelos Animais de Doenças , Ecocardiografia , Ventrículos do Coração/patologia , Ventrículos do Coração/fisiopatologia , Hipertrofia Ventricular Esquerda/etiologia , Hipertrofia Ventricular Esquerda/metabolismo , Hipóxia/metabolismo , Hipóxia/fisiopatologia , Indóis , Contração Miocárdica/fisiologia , Ratos Wistar , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/análise , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Fatores de Tempo , Disfunção Ventricular Esquerda/etiologia , Disfunção Ventricular Esquerda/metabolismo , Remodelação Ventricular/fisiologiaRESUMO
Obesity has been shown to impair myocardial performance. Nevertheless, the mechanisms underlying the participation of calcium (Ca(2+) ) handling on cardiac dysfunction in obesity models remain unknown. L-type Ca(2+) channels and sarcoplasmic reticulum (SR) Ca(2+) -ATPase (SERCA2a), may contribute to the cardiac dysfunction induced by obesity. The purpose of this study was to investigate whether myocardial dysfunction in obese rats is related to decreased activity and/or expression of L-type Ca(2+) channels and SERCA2a. Male 30-day-old Wistar rats were fed standard (C) and alternately four palatable high-fat diets (Ob) for 15 weeks. Obesity was determined by adiposity index and comorbidities were evaluated. Myocardial function was evaluated in isolated left ventricle papillary muscles under basal conditions and after inotropic and lusitropic maneuvers. L-type Ca(2+) channels and SERCA2a activity were determined using specific blockers, while changes in the amount of channels were evaluated by Western blot analysis. Phospholamban (PLB) protein expression and the SERCA2a/PLB ratio were also determined. Compared with C rats, the Ob rats had increased body fat, adiposity index and several comorbidities. The Ob muscles developed similar baseline data, but myocardial responsiveness to post-rest contraction stimulus and increased extracellular Ca(2+) was compromised. The diltiazem promoted higher inhibition on developed tension in obese rats. In addition, there were no changes in the L-type Ca(2+) channel protein content and SERCA2a behavior (activity and expression). In conclusion, the myocardial dysfunction caused by obesity is related to L-type Ca(2+) channel activity impairment without significant changes in SERCA2a expression and function as well as L-type Ca(2+) protein levels.
Assuntos
Canais de Cálcio Tipo L/fisiologia , Cardiomiopatias/fisiopatologia , Obesidade/complicações , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/fisiologia , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo L/biossíntese , Proteínas de Ligação ao Cálcio/metabolismo , Cardiomiopatias/etiologia , Gorduras na Dieta/administração & dosagem , Diltiazem/farmacologia , Masculino , Contração Miocárdica/efeitos dos fármacos , Obesidade/fisiopatologia , Ratos , Ratos Wistar , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/antagonistas & inibidoresRESUMO
Simultaneous recording of cytosolic and sarco-endoplasmic reticulum (SR/ER) luminal free calcium concentrations ([Ca(2+)](i) and [Ca(2+)](L), respectively) supports the notion that release channels (RyRs and IP(3)Rs) use a concealed Ca(2+) source, likely to be associated with intra-SR/ER Ca(2+) binding proteins, whereas SR/ER Ca(2+) leak channels can only access free luminal Ca(2+). We hypothesize that Ca(2+) is trapped by oligomers of luminal Ca(2+)-binding proteins and that the opening of release channels induces the rapid liberation of this "concealed" Ca(2+) source associated with intra-ER Ca(2+) buffers. Our hypothesis may also clarify why SERCA pumps potentiate Ca(2+) release and explain quantal characteristics and refractory states of Ca(2+) release process.
Assuntos
Canais de Cálcio/fisiologia , Sinalização do Cálcio/fisiologia , Cálcio/fisiologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/fisiologia , Retículo Sarcoplasmático/metabolismo , Animais , Cálcio/metabolismo , Canais de Cálcio/metabolismo , Humanos , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Retículo Sarcoplasmático/enzimologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismoRESUMO
Previous studies have shown that food restriction promotes myocardial dysfunction in rats. However, the molecular mechanisms that are responsible are unclear. We investigated the role of sarcoplasmic reticulum Ca2+-ATPase (SERCA2) on myocardial performance in food-restricted rats. Male Wistar-Kyoto rats, 60 days old, were fed a control or restricted diet (daily energy intake reduced to 50% of the control) for 90 days. Expression of Serca2a, phospholamban (PLB), Na+/Ca2+ exchanger (NCX), and thyroid hormone receptor (TRalpha1, TRbeta1) mRNA was determined by quantitative PCR. SERCA2 activity was measured by using 20 micromol/L cyclopiazonic acid (CPA) in a left ventricular papillary muscle preparation during isometric contraction in basal conditions and during post-rest contraction. Serum concentrations of thyroxine (T4) and thyrotropin (TSH) were also determined. The 50%-restricted diet reduced body and ventricular weight and serum T4 and TSH levels. The interaction of CPA and food restriction reduced peak developed tension and maximum rate of tension decline (-dT/dt), but increased the resting tension intensity response during post-rest contraction. PLB and NCX mRNA were upregulated and TRalpha1 mRNA was downregulated by food restriction. These results suggest that food restriction promotes myocardial dysfunction related to impairment of sarcoplasmic reticulum Ca2+ uptake as a result of a hypothyroid state.