RESUMO
Previously, we have shown that an increased cGMP-activated protein Kinase (PKG) activity after phosphodiesterase 5 (PDE5) inhibition by Sildenafil (SIL), leads to myocardial Na+/H+ exchanger (NHE1) inhibition preserving its basal homeostatic function. Since NHE1 is hyperactive in the hypertrophied myocardium of spontaneous hypertensive rats (SHR), while its inhibition was shown to prevent and revert this pathology, the current study was aimed to evaluate the potential antihypertrophic effect of SIL on adult SHR myocardium. We initially tested the inhibitory capability of SIL on NHE1 in isolated cardiomyocytes of SHR by comparing H+ efflux during the recovery from an acid load. After confirmed that effect, eight-month-old SHR were chronically treated for one month with SIL through drinking water. Compared to their littermate controls, SIL-treated rats presented a decreased NHE1 activity, which correlated with a reduction in its phosphorylation level assigned to activation of a PKG-p38 MAP kinase-PP2A signaling pathway. Moreover, treated animals showed a decreased oxidative stress that appears to be a consequence of a decreased mitochondrial NHE1 phosphorylation. Treated SHR showed a significant reduction in the pro-hypertrophic phosphatase calcineurin, despite slight tendency to decrease hypertrophy was detected. When SIL treatment was prolonged to three months, a significant decrease in myocardial hypertrophy and interstitial fibrosis that correlated with a lower myocardial stiffness was observed. In conclusion, the current study provides evidence concerning the ability of SIL to revert established cardiac hypertrophy in SHR, a clinically relevant animal model that resembles human essential hypertension.
Assuntos
Cardiomegalia/prevenção & controle , Miócitos Cardíacos/efeitos dos fármacos , Músculos Papilares/efeitos dos fármacos , Inibidores da Fosfodiesterase 5/farmacologia , Citrato de Sildenafila/farmacologia , Trocador 1 de Sódio-Hidrogênio/metabolismo , Animais , Cardiomegalia/enzimologia , Cardiomegalia/etiologia , Cardiomegalia/fisiopatologia , Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , Modelos Animais de Doenças , Regulação para Baixo , Fibrose , Hipertensão/complicações , Masculino , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/patologia , Músculos Papilares/enzimologia , Músculos Papilares/fisiopatologia , Fosforilação , Proteína Fosfatase 2/metabolismo , Ratos Endogâmicos SHR , Transdução de Sinais , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Copper is an essential metal for homeostasis and the functioning of living organisms. We investigated the effects of a high copper concentration on the myocardial mechanics, investigating the reactive oxygen species (ROS) mediated effects. The developed force of papillary muscles was reduced after acute exposure to a high copper concentration and was prevented by co-incubation with tempol, DMSO and catalase. The reuptake of calcium by the sarcoplasmic reticulum was reduced by copper and restored by tempol. The contractile response to Ca2+ was reduced and reversed by antioxidants. The response to the ß-adrenergic agonist decreased after exposure to copper and was restored by tempol and catalase. In addition, the in situ detection showed increased O2·- and OH·. Contractions dependent on the sarcolemmal Ca2+ influx were impaired by copper and restored by antioxidants. Myosin-ATPase activity decreased significantly after copper exposure. In conclusion, a high copper concentration can acutely impair myocardial excitation-contraction coupling, reduce the capacity to generate force, reduce the Ca2+ inflow and its reuptake, and reduce myosin-ATPase activity, and these effects are mediated by the local production of O2·-, OH· and H2O2. These toxicity effects of copper overload suggest that copper is a risk factor for cardiovascular disease.
Assuntos
Cobre/toxicidade , Músculos Papilares/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Animais , Cálcio/metabolismo , Masculino , Contração Miocárdica/efeitos dos fármacos , Miosinas/metabolismo , Músculos Papilares/metabolismo , Músculos Papilares/fisiologia , Ratos Wistar , Retículo Sarcoplasmático/efeitos dos fármacos , Retículo Sarcoplasmático/metabolismoRESUMO
Iron intoxication is related to reactive oxygen species (ROS) production and organic damage including the cardiovascular system, and is a leading cause of poisoning deaths in children. In this study we examined whether a range of ferrous iron (Fe(2+)) concentrations can interfere differently on the myocardial mechanics, investigating the ROS-mediated effects. Developed force of isolated rat papillary muscles was depressed with a concentration- and time-dependency by Fe(2+) 100-1000µM. The contractile response to Ca(2+) was reduced, but it was partially reversed by co-incubation with catalase and DMSO, but not TEMPOL. In agreement, in situ detection of OH was increased by Fe(2+) whereas O2(-) was unchanged. The myosin-ATPase activity was significantly decreased. Contractions dependent on the sarcolemal Ca(2+) influx were impaired only by Fe(2+) 1000µM, and antioxidants had no effect. In skinned fibers, Fe(2+) reduced the pCa-force relationship, and pCa50 was right-shifted by 0.55. In conclusion, iron overload can acutely impair myocardial contractility by reducing myosin-ATPase activity and myofibrillar Ca(2+) sensitivity. These effects are mediated by local production of OH and H2O2. Nevertheless, in a such high concentration as 1000µM, Fe(2+) appears to depress force also by reducing Ca(2+) influx, probably due to a competition at Ca(2+) channels.
Assuntos
Compostos Ferrosos/farmacologia , Contração Miocárdica/efeitos dos fármacos , Músculos Papilares/efeitos dos fármacos , Animais , Cálcio/metabolismo , Técnicas In Vitro , Sobrecarga de Ferro/metabolismo , Sobrecarga de Ferro/fisiopatologia , Contração Isométrica/efeitos dos fármacos , Masculino , Miosinas/metabolismo , Músculos Papilares/metabolismo , Músculos Papilares/fisiologia , Ratos Wistar , Espécies Reativas de Oxigênio/metabolismoRESUMO
Fish venom cytolysins are multifunctional proteins that in addition to their cytolytic/hemolytic effects display neurotoxic, cardiotoxic and inflammatory activities, being described as "protein lethal factors". A pore-forming cytolysin called Sp-CTx (Scorpaena plumieriCytolytic Toxin) has been recently purified from the venom of the scorpionfish Scorpaena plumieri. It is a glycoprotein with dimeric constitution, comprising subunits of approximately 65 kDa. Previous studies have revealed that this toxin has a vasorelaxant activity that appears to involve the L-arginine-nitric oxide synthase pathway; however its cardiovascular effects have not been fully comprehended. The present study examined the cardiovascular effects of Sp-CTx in vivo and in vitro. In anesthetized rats Sp-CTx (70 µg/kg i.v) produced a biphasic response which consisted of an initial systolic and diastolic pressure increase followed by a sustained decrease of these parameters and the heart rate. In isolated rats hearts Sp-CTx (10(-9) to 5 × 10(-6) M) produced concentration-dependent and transient ventricular positive inotropic effect and vasoconstriction response on coronary bed. In papillary muscle, Sp-CTx (10(-7) M) also produced an increase in contractile isometric force, which was attenuated by the catecholamine releasing agent tyramine (100 µM) and the ß-adrenergic antagonist propranolol (10 µM). On isolated ventricular cardiomyocytes Sp-CTx (1 nM) increased the L-type Ca(2+) current density. The results show that Sp-CTx induces disorders in the cardiovascular system through increase of sarcolemmal calcium influx, which in turn is partially caused by the release of endogenous noradrenaline.
Assuntos
Cardiotoxinas/toxicidade , Circulação Coronária/efeitos dos fármacos , Venenos de Peixe/química , Coração/efeitos dos fármacos , Músculos Papilares/efeitos dos fármacos , Perciformes , Perforina/toxicidade , Animais , Pressão Sanguínea/efeitos dos fármacos , Brasil , Cardiotoxinas/administração & dosagem , Cardiotoxinas/isolamento & purificação , Células Cultivadas , Proteínas de Peixes/administração & dosagem , Proteínas de Peixes/isolamento & purificação , Proteínas de Peixes/toxicidade , Glicoproteínas/administração & dosagem , Glicoproteínas/isolamento & purificação , Glicoproteínas/toxicidade , Coração/fisiologia , Frequência Cardíaca/efeitos dos fármacos , Técnicas In Vitro , Injeções Intravenosas , Masculino , Contração Muscular/efeitos dos fármacos , Miócitos Cardíacos/citologia , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Músculos Papilares/fisiologia , Técnicas de Patch-Clamp , Perforina/administração & dosagem , Perforina/isolamento & purificação , Ratos Wistar , Vasoconstritores/administração & dosagem , Vasoconstritores/isolamento & purificação , Vasoconstritores/toxicidadeRESUMO
Obesity has been shown to impair myocardial performance. Some factors have been suggested as responsible for possible cardiac abnormalities in models of obesity, among them beta-adrenergic (ßA) system, an important mechanism of regulation of myocardial contraction and relaxation. The objective of present study was to evaluate the involvement of ßA system components in myocardial dysfunction induced by obesity. Thirty-day-old male Wistar rats were distributed in control (C, n = 25) and obese (Ob, n = 25) groups. The C group was fed a standard diet and Ob group was fed four unsaturated high-fat diets for 15 weeks. Cardiac function was evaluated by isolated papillary muscle preparation and ßA system evaluated by using cumulative concentrations of isoproterenol and Western blot. After 15 weeks, the Ob rats developed higher adiposity index than C rats and several comorbidities; however, were not associated with changes in systolic blood pressure. Obesity caused structural changes and the myocardial responsiveness to post-rest contraction stimulus and increased extracellular calcium (Ca2+) was compromised. There were no changes in cardiac function between groups after ßA stimulation. The obesity was not accompanied by changes in protein expression of G protein subunit alpha (Gsα) and ßA receptors (ß1AR and ß2AR). In conclusion, the myocardial dysfunction caused by unsaturated high-fat diet-induced obesity, after 15 weeks, is not related to ßAR system impairment at the receptor-signalling pathway.
Assuntos
Coração/fisiopatologia , Obesidade/fisiopatologia , Músculos Papilares/fisiopatologia , Receptores Adrenérgicos beta/metabolismo , Adiposidade/efeitos dos fármacos , Agonistas Adrenérgicos beta/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Western Blotting , Cálcio/farmacologia , Dieta Hiperlipídica/efeitos adversos , Subunidades alfa Gs de Proteínas de Ligação ao GTP/metabolismo , Coração/efeitos dos fármacos , Isoproterenol/farmacologia , Masculino , Contração Miocárdica/efeitos dos fármacos , Obesidade/etiologia , Obesidade/metabolismo , Músculos Papilares/efeitos dos fármacos , Músculos Papilares/metabolismo , Ratos Wistar , Transdução de Sinais/efeitos dos fármacos , Fatores de TempoRESUMO
PURPOSE: To study racemic bupivacaine, non-racemic bupivacaine and ropivacaine on myocardial contractility. METHODS: Isolated Wistar papillary muscles were submitted to 50 and 100 mM racemic bupivacaine (B50 and B100), non-racemic bupivacaine (NR50 and NR100) and ropivacaine (R50 and R100) intoxication. Isometric contraction data were obtained in basal condition (0.2 Hz), after increasing the frequency of stimulation to 1.0 Hz and after 5, 10 and 15 min of local anesthetic intoxication. Data were analyzed as relative changes of variation. RESULTS: Developed tension was higher with R100 than B100 at D1 (4.3 ± 41.1 vs -57.9 ± 48.1). Resting tension was altered with B50 (-10.6 ± 23.8 vs -4.7 ± 5.0) and R50 (-14.0 ± 20.5 vs -0.5 ± 7.1) between D1 and D3. Maximum rate of tension development was lower with B100 (-56.6 ± 38.0) than R50 (-6.3 ± 37.9) and R100 (-1.9 ± 37.2) in D1. B50, B100 and NR100 modified the maximum rate of tension decline from D1 through D2. Time to peak tension was changed with NR50 between D1 and D2. CONCLUSIONS: Racemic bupivacaine depressed myocardial contractile force more than non-racemic bupivacaine and ropivacaine. Non-racemic and racemic bupivacaine caused myocardial relaxation impairment more than ropivacaine.
Assuntos
Amidas/farmacologia , Anestésicos Locais/farmacologia , Bupivacaína/farmacologia , Contração Miocárdica/efeitos dos fármacos , Animais , Bupivacaína/química , Depressão Química , Masculino , Tono Muscular/efeitos dos fármacos , Tono Muscular/fisiologia , Contração Miocárdica/fisiologia , Músculos Papilares/efeitos dos fármacos , Músculos Papilares/fisiologia , Ratos Wistar , Valores de Referência , Ropivacaina , Estereoisomerismo , Fatores de TempoRESUMO
BACKGROUND: Oxidative stress plays a major role in diabetic cardiomyopathy pathogenesis. Anti-oxidant therapy has been investigated in preventing or treating several diabetic complications. However, anti-oxidant action on diabetic-induced cardiac remodeling is not completely clear. This study evaluated the effects of rutin, a flavonoid, on cardiac and myocardial function in diabetic rats. METHODS: Wistar rats were assigned into control (C, n = 14); control-rutin (C-R, n = 14); diabetes mellitus (DM, n = 16); and DM-rutin (DM-R, n = 16) groups. Seven days after inducing diabetes (streptozotocin, 60 mg/kg, i.p.), rutin was injected intraperitoneally once a week (50 mg/kg) for 7 weeks. Echocardiogram was performed and myocardial function assessed in left ventricular (LV) papillary muscles. Serum insulin concentration was measured by ELISA. STATISTICS: One-way ANOVA and Tukey's post hoc test. RESULTS: Glycemia was higher in DM than DM-R and C and in DM-R than C-R. Insulin concentration was lower in diabetic groups than controls (C 2.45 ± 0.67; C-R 2.09 ± 0.52; DM 0.59 ± 0.18; DM-R 0.82 ± 0.21 ng/mL). Echocardiogram showed no differences between C-R and C. DM had increased LV systolic diameter compared to C, and increased left atrium diameter/body weight (BW) ratio and LV mass/BW ratio compared to C and DM-R. Septal wall thickness, LV diastolic diameter/BW ratio, and relative wall thickness were lower in DM-R than DM. Fractional shortening and posterior wall shortening velocity were lower in DM than C and DM-R. In papillary muscle preparation, DM and DM-R presented higher time to peak tension and time from peak tension to 50% relaxation than controls; time to peak tension was lower in DM-R than DM. Under 0.625 and 1.25 mM extracellular calcium concentrations, DM had higher developed tension than C. CONCLUSION: Rutin attenuates cardiac remodeling and left ventricular and myocardial dysfunction caused by streptozotocin-induced diabetes mellitus.
Assuntos
Antioxidantes/farmacologia , Diabetes Mellitus Experimental/tratamento farmacológico , Cardiomiopatias Diabéticas/prevenção & controle , Contração Miocárdica/efeitos dos fármacos , Músculos Papilares/efeitos dos fármacos , Rutina/farmacologia , Função Ventricular Esquerda/efeitos dos fármacos , Animais , Biomarcadores/sangue , Glicemia/metabolismo , Cálcio/metabolismo , Diabetes Mellitus Experimental/sangue , Diabetes Mellitus Experimental/complicações , Cardiomiopatias Diabéticas/sangue , Cardiomiopatias Diabéticas/etiologia , Cardiomiopatias Diabéticas/fisiopatologia , Insulina/sangue , Masculino , Músculos Papilares/metabolismo , Músculos Papilares/fisiopatologia , Ratos Wistar , Remodelação Ventricular/efeitos dos fármacosRESUMO
PURPOSE: To study racemic bupivacaine, non-racemic bupivacaine and ropivacaine on myocardial contractility. METHODS: Isolated Wistar papillary muscles were submitted to 50 and 100 mM racemic bupivacaine (B50 and B100), non-racemic bupivacaine (NR50 and NR100) and ropivacaine (R50 and R100) intoxication. Isometric contraction data were obtained in basal condition (0.2 Hz), after increasing the frequency of stimulation to 1.0 Hz and after 5, 10 and 15 min of local anesthetic intoxication. Data were analyzed as relative changes of variation. RESULTS: Developed tension was higher with R100 than B100 at D1 (4.3 ± 41.1 vs -57.9 ± 48.1). Resting tension was altered with B50 (-10.6 ± 23.8 vs -4.7 ± 5.0) and R50 (-14.0 ± 20.5 vs -0.5 ± 7.1) between D1 and D3. Maximum rate of tension development was lower with B100 (-56.6 ± 38.0) than R50 (-6.3 ± 37.9) and R100 (-1.9 ± 37.2) in D1. B50, B100 and NR100 modified the maximum rate of tension decline from D1 through D2. Time to peak tension was changed with NR50 between D1 and D2. CONCLUSIONS: Racemic bupivacaine depressed myocardial contractile force more than non-racemic bupivacaine and ropivacaine. Non-racemic and racemic bupivacaine caused myocardial relaxation impairment more than ropivacaine. .
Assuntos
Animais , Masculino , Amidas/farmacologia , Anestésicos Locais/farmacologia , Bupivacaína/farmacologia , Contração Miocárdica/efeitos dos fármacos , Bupivacaína/química , Depressão Química , Tono Muscular/efeitos dos fármacos , Tono Muscular/fisiologia , Contração Miocárdica/fisiologia , Músculos Papilares/efeitos dos fármacos , Músculos Papilares/fisiologia , Ratos Wistar , Valores de Referência , Estereoisomerismo , Fatores de TempoRESUMO
New bioactive N-acylhydrazone derivatives synthesized from safrole previously have been found to promote intense vasodilation and antihypertensive activity. In this study, we describe the synthesis and the cardiovascular effects of the new N-acylhydrazone derivative (E)-N-methyl-N'-(thiophen-3-ylmethylene)benzo[d][1,3]dioxole-5-carbohydrazide (LASSBio-1289). Thoracic aorta and left papillary muscles from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were prepared for isometric tension recording. LASSBio-1289 promoted relaxation of endothelium-intact and denuded aortic rings with respective pIC50 (-log IC50) values of 5.07 ± 0.09 and 4.26 ± 0.09 (P < 0.001) for WKY rats and 5.43 ± 0.05 and 5.58 ± 0.07 (P > 0.05) for SHR. The vasodilator activity of LASSBio-1289 was increased in the KCl-contracted aorta. LASSBio-1289 attenuated the contracture elicited by Ca(2+) in depolarized aorta from both WKY rats and SHR. In endothelium-intact aorta from WKY rats, LASSBio-1289-induced relaxation was unchanged after incubation with propranolol, ZM 241385, atropine, diphenhydramine, and HOE140, but was significantly reduced by L-NAME and ODQ. LASSBio-1289 decreased papillary muscles contractility only at concentrations above 200 µm. Acute intravenous injection of LASSBio-1289 (3 mg/kg) produced a significant hypotensive response in SHR but not in WKY rats, suggesting its antihypertensive profile. The antihypertensive effect was also observed in SHR during 14 days of intraperitoneal and oral administration. In conclusion, our data demonstrated that LASSBio-1289 induces both endothelium-independent vasorelaxation involving the inhibition of Ca(2+) influx through L-type Ca(2+) channels in aorta from WKY rats and SHR, and endothelium-dependent relaxation mediated by the NO/cyclic GMP pathway in WKY rats.
Assuntos
Anti-Hipertensivos/farmacologia , Benzodioxóis/farmacologia , Canais de Cálcio Tipo L/metabolismo , Hidrazonas/farmacologia , Vasodilatadores/farmacologia , Animais , Aorta Torácica/efeitos dos fármacos , Aorta Torácica/metabolismo , Cálcio/metabolismo , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/metabolismo , Masculino , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Músculos Papilares/efeitos dos fármacos , Músculos Papilares/metabolismo , Cloreto de Potássio/metabolismo , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY , Vasodilatação/efeitos dos fármacosRESUMO
BACKGROUND: The role of aldosterone blockers during transition from long-term compensated hypertrophy to dilated failure is not completely understood. In this study we evaluated the effects of early administration of spironolactone on cardiac remodeling, myocardial function, and mortality in spontaneously hypertensive rats (SHR). METHODS: Sixteen-month-old SHR received no treatment (SHR-C, n=72) or spironolactone (SHR-SPR, 20 mg/kg/day, n=34) for six months. Echocardiogram was performed before and after treatment. Myocardial function was analyzed in left ventricular (LV) papillary muscle preparations. Myocardial collagen and hydroxyproline concentration were evaluated by morphometry and spectrophotometry, respectively. LV gene expression was assessed by real time RT-PCR. STATISTICS: Student's t test; Log rank test (Kaplan Meyer). RESULTS: SHR-C and SHR-SPR presented mortality rates of 71 and 38%, respectively (p=0.004). Systolic arterial pressure did not differ between groups (SHR-C 199±43; SHR-SPR 200±35 mmHg). Initial and final echocardiograms did not show significant differences in cardiac structures or LV function between groups. Myocardial function was similar between groups at basal and after inotropic stimulation. Collagen fractional area, hydroxyproline concentration, gene expression for α- and ß-myosin heavy chain, atrial natriuretic peptide, and Serca2a were not different between groups. CONCLUSION: Early spironolactone administration reduces mortality without changing cardiac remodeling in spontaneous hypertensive rats.