Chronic aerobic exercise associated to low-dose L-NAME improves contractility without changing calcium handling in rat cardiomyocytes

Nitric oxide (NO) inhibition by high-dose NG-nitro-L-arginine methyl ester (L-NAME) is associated with several detrimental effects on the cardiovascular system. However, low-dose L-NAME increases NO synthesis, which in turn induces physiological cardiovascular benefits, probably by activating a protective negative feedback mechanism. Aerobic exercise, likewise, improves several cardiovascular functions in healthy hearts, but its effects are not known when chronically associated with low-dose L-NAME. Thus, we tested whether the association between low-dose L-NAME administration and chronic aerobic exercise promotes beneficial effects to the cardiovascular system, evaluating the cardiac remodeling process. Male Wistar rats were randomly assigned to control (C), L-NAME (L), chronic aerobic exercise (Ex), and chronic aerobic exercise associated to L-NAME (ExL). Aerobic training was performed with progressive intensity for 12 weeks; L-NAME (1.5 mg·kg-1·day-1) was administered by orogastric gavage. Low-dose L-NAME alone did not change systolic blood pressure (SBP), but ExL significantly increased SBP at week 8 with normalization after 12 weeks. Furthermore, ExL promoted the elevation of left ventricle (LV) end-diastolic pressure without the presence of cardiac hypertrophy and fibrosis. Time to 50% shortening and relaxation were reduced in ExL, suggesting a cardiomyocyte contractile improvement. In addition, the time to 50% Ca2+ peak was increased without alterations in Ca2+ amplitude and time to 50% Ca2+ decay. In conclusion, the association of chronic aerobic exercise and low-dose L-NAME prevented cardiac pathological remodeling and induced cardiomyocyte contractile function improvement; however, it did not alter myocyte affinity and sensitivity to intracellular Ca2+ handling.

Bradycardic and Antiarrhythmic Effects of the D-Limonene in Rats / Efeitos Bradicárdicos e Antiarrítmicos do D-Limoneno em Ratos

Abstract Background: D-limonene (DL) is a monoterpene and is the major component in the essential oil of citrus fruit. It presents antihyperglycemic and vasodilatation activities. Objectives: This study evaluated the cardiovascular effects and potential antiarrhythmic of DL in rats. Methods: Hemodynamic and electrocardiographic (ECG) parameters were measured in male Wistar rats, which under anesthesia had been cannulated in the abdominal aorta and lower vena cava and had electrodes subcutaneously implanted. In the in vitro approach, the heart was removed and perfused using the Langendorff technique. The significance level adopted was 5% (p < 0.05). Results: DL, in doses of 10, 20, and 40 mg/kg (i.v), produced intense and persistent bradycardia associated with hypotension. Bradycardia with prolonged QTc was observed in the ECG in vivo recording. In the in vivo model of arrhythmia induced by Bay K8644, DL (10 mg/kg) decreased the arrhythmia score from 15.33 ± 3.52 to 4.0 ± 2.64 u.a (p < 0.05, n = 4). In isolated perfused hearts, DL (10-3 M) promoted significant reductions in heart rate (from 228.6 ± 8.5 ms to 196.0 ± 9.3 bpm; p < 0.05) and left ventricular development pressure (from 25.2 ± 3.4 to 5.9 ± 1.8 mmHg; n = 5, p < 0.05). Conclusions: DL produces bradycardia and antiarrhythmic activity in rat heart.

Resumo Fundamento: O D-limoneno (DL) é um monoterpeno e o principal componente do óleo essencial de frutas cítricas. Ele apresenta atividades anti-hiperglicêmicas e vasodilatadoras. Objetivos: Este estudo avaliou os efeitos cardiovasculares e antiarrítmicos potenciais do DL em ratos. Métodos: Os parâmetros hemodinâmicos e eletrocardiográficos (ECG) foram mensurados em ratos Wistar machos que, sob anestesia, tiveram a aorta abdominal e a veia cava inferior canuladas e receberam eletrodos implantados subcutaneamente. Na abordagem in vitro, o coração foi removido e perfundido utilizando a técnica de Langendorff. O nível de significância adotado foi de 5% (p < 0,05). Resultados: DL, nas doses de 10, 20 e 40 mg/kg (i.v), produziu bradicardia intensa e persistente associada à hipotensão. A bradicardia com QTc prolongado foi observada no registro in vivo do ECG. No modelo in vivo de arritmia induzida por Bay K8644, DL (10 mg / kg) houve diminuição do escore da arritmia de 15,33 ± 3,52 para 4,0 ± 2,64 u.a (p < 0,05, n = 4). Em corações perfundidos isolados, o DL (10-3 M) promoveu reduções significativas na frequência cardíaca (de 228,6 ± 8,5 ms para 196,0 ± 9,3 bpm; p < 0,05) e na pressão desenvolvida do ventrículo esquerdo (de 25,2 ± 3,4 para 5,9 ± 1,8 mmHg; n = 5, p < 0,05). Conclusões: O DL produz bradicardia e atividade antiarrítmica no coração de ratos.

Effects of spironolactone in spontaneously hypertensive adult rats subjected to high salt intake

OBJECTIVE: To evaluate the effect of spironolactone on ventricular stiffness in spontaneously hypertensive adult rats subjected to high salt intake. INTRODUCTION: High salt intake leads to cardiac hypertrophy, collagen accumulation and diastolic dysfunction. These effects are partially mediated by cardiac activation of the renin-angiotensin-aldosterone system. METHODS: Male spontaneously hypertensive rats (SHRs, 32 weeks) received drinking water (SHR), a 1 percent NaCl solution (SHR-Salt), or a 1 percent NaCl solution with a daily subcutaneous injection of spironolactone (80 mg.kg-1) (SHRSalt- S). Age-matched normotensive Wistar rats were used as a control. Eight weeks later, the animals were anesthetized and catheterized to evaluate left ventricular and arterial blood pressure. After cardiac arrest, a doublelumen catheter was inserted into the left ventricle through the aorta to obtain in situ left ventricular pressurevolume curves. RESULTS: The blood pressures of all the SHR groups were similar to each other but were different from the normotensive controls (Wistar = 109±2; SHR = 118±2; SHR-Salt = 117±2; SHR-Salt-S = 116±2 mmHg; P<0.05). The cardiac hypertrophy observed in the SHR was enhanced by salt overload and abated by spironolactone (Wistar = 2.90±0.06; SHR = 3.44±0.07; SHR-Salt = 3.68±0.07; SHR-Salt-S = 3.46±0.05 mg/g; P<0.05). Myocardial relaxation, as evaluated by left ventricular dP/dt, was impaired by salt overload and improved by spironolactone (Wistar = -3698±92; SHR = -3729±125; SHR-Salt = -3342±80; SHR-Salt-S = -3647±104 mmHg/s; P<0.05). Ventricular stiffness was not altered by salt overload, but spironolactone treatment reduced the ventricular stiffness to levels observed in the normotensive controls (Wistar = 1.40±0.04; SHR = 1.60±0.05; SHR-Salt = 1.67±0.12; SHR-Salt- S = 1.45±0.03 mmHg/ml; P<0.05). CONCLUSION: Spironolactone reduces left ventricular hypertrophy secondary to high salt intake and ventricular stiffness in adult SHRs.

Carbamazepine does not alter the intrinsic cardiac function in rats with epilepsy / Carbamazepina não altera o funcionamento cardíaco intrínseco em ratos com epilepsia

Among the causes for sudden unexpected death (SUDEP) in epilepsy, the effects of antiepileptic drugs on the heart have been poorly explored. Based on this, the aim of our study was to evaluate the heart rate (in vivo and isolated ex vivo) and ventricular pressure (isolated ex vivo) of rats with and without epilepsy treated with carbamazepine. Four groups of adult, male Wistar rats (200-250 g) were studied: [A] control rats (n=8), received neither pilocarpine nor carbamazepine [B] carbamazepine-treated rats (n=8), received a daily dose of 120 mg/Kg, i.p. of carbamazepine for two weeks; [C] rats with epilepsy that received just saline solution (n=8); [D] rats with epilepsy that received a daily dose of 120 mg/Kg, i.p. of carbamazepine for two weeks (n=8). Our results showed significant increase in heart rate in animals with epilepsy (with and without the use of carbamazepine) when compared to the control groups in vivo. In contrast, we did not find differences during isolated ex vivo experiments comparing animals with and without epilepsy and despite the use of carbamazepine. Our results suggest that, in isolation, carbamazepine may not be a potential risk factor for sudden unexpected death in epilepsy.

Entre as causas de morte súbita em epilepsia (SUDEPE), os efeitos das drogas antiepilépticas no coração têm sido pobremente explorados. Desta forma, o objetivo deste estudo foi avaliar a frequência cardíaca (in vivo e de forma isolada ex vivo) e a pressão ventricular (de forma isolada ex vivo) de ratos com e sem epilepsia tratados com carbamazepina. Quatro grupos de ratos Wistar machos adultos (peso 200 a 250 g) foram estudados: [A] ratos controle (n=8), não receberam pilocarpina ou carbamazepina; [B] ratos tratados com carbamazepina (n=8), receberam dose diária de carbamazepina de 120 mg/kg intraperitoneal, durante duas semanas (n=8); [C] ratos com epilepsia que receberam solução salina; [D] ratos com epilepsia que receberam dose diária de carbamazepina de 120 mg/kg intraperitoneal durante duas semanas. Nossos resultados evidenciaram uma diferença estatisticamente significativa na média da freqüência cardíaca in vivo entre os animais com epilepsia (com e sem o uso de carbamazepina) quando comparados aos grupos controles in vivo. Em contraste, não observamos diferenças estatísticas nos experimentos ex vivo quando comparados os animais com ou sem epilepsia, a despeito do uso da carbamazepina. Nossos resultados sugerem que, de forma isolada, a carbamazepina pode não ser um fator de risco potencial para a ocorrência de morte súbita em epilepsia.

Effects of Nigella sativa supplementation for one month on cardiac reserve in rats.

Nigella sativa (N. sativa) has a long history of use in folk medicine. In a current study performed in this laboratory, two-month dietary supplementation with N. sativa extract to normal rats has shown a homogenous cardiac hypertrophy and enhanced cardiac contractility at baseline conditions. In the present study, shorter (one-month) duration of oral N. sativa administration was adopted to detect possible earlier cardiac responses. In addition, in vitro cardiac stress by the beta adrenoceptor agonist isoproterenol was used to assess the intrinsic cardiac reserve mechanisms. The hearts of Nigella-treated rats developed a moderate but significant hypertrophy that was evident by an increase in the heart weight to body weight ratio. The observed Nigella-induced cardiac hypertrophy was associated with an increase in the baseline cardiac inotropic properties as well as the maximal peak tension generation upon progressive cardiac stress by isoproterenol infusion. The demonstrated selective enhancement of the inotropic reserve favours the physiological nature of Nigella-induced cardiac hypertrophy, similar to that provoked by exercise training.

Myocardial protection by continuous, blood, antegrade-retrograde cardioplegia in rabbits

PURPOSE: To study the effectiveness of the continuous, blood, antegrade-retrograde cardioplegia in an experimental model of isolated heart, evaluating ventricular function. METHODS: Rabbits were divided into four groups: Control-C(n=10); ischemic crystalloid cardioplegia-IC(n=10); ischemic blood cardioplegia-IB(n=10); ischemic non cardioplegia-INC(n=10). After the ischemic protocol period the ventricular function was analyzed by the intra-ventricular balloon technique. RESULTS: the intra-ventricular developed pressure (IVDP) was: C(92.90±6.86mmHg); IC(77.78±6.15mmHg); IB(93.64±5.09mmHg); INC(39.46 ±8.91mmHg) p<0.005. The first derivative of intra-ventricular pressure in its positive deflection was: C(1137.50± 92.23mmHg/sec); IC(1130.62 ±43.78mmHg/sec); IB(1187.58± 88.38mmHg/sec); INC(620.02± 43.80mmHg/se) p<0.005. The first derivate pressure in its negative deflection was: C(770.00± 73.41mmHg/sec); IC(610.03 ±47.43mmg/sec); IB(762.53 ±46.02mmHg/sec); INC(412.35 ±84.36mmHg/sec) p<0,005. The stress-strain angular logarithmic coefficient was: C(0.108± 0.02); IC(0.159± 0.038); IB(0.114 ±0.016); INC(0.175± 0.038) p<0.05. CONCLUSION: The ischemic group protected by blood cardioplegia showed better ventricular function than ischemic group protected by crystalloid cardioplegia and the non protected group.

OBJETIVO: Estudar a eficácia e a segurança da cardioplegia sanguínea, aterógrada-retrógrada contínua, por meio da avaliação da função ventricular. MÉTODOS: Os coelhos foram divididos em quatro grupos: Controle-C(n=10); isquêmico e cardioplegia cristaloide-IC(n=10; isquêmico e cardioplegia sanguínea-IB(n=10; isquêmico sem cardioplegia-INC(n=10. Após o período isquêmico do protocolo a função ventricular foi analisada pela técnica do balão intra-ventricular. RESULTADOS: a pressão desenvolvida intra-ventricular (IVDP) foi: C(92,90± 6,86mmHg); IC(77,78± 6,15mmHg); IB(93,64 ±5,09mmHg); INC(39,46 ±8,91mmHg) p<0,005. a primeira derivada temporal da pressão ventricular na sua deflexão positiva: C(1137,50± 92,23mmHg/sec); IC(1130,62 ±43,78mmHg/sec); IB(1187,58± 88,38mmHg/sec); INC(620,02± 43,80mmHg/se) p<0,005. A primeira derivada da pressão ventricular na sua deflexão negativa: C(770,00± 73,41mmHg/sec); IC(610,03 ±47,43mmg/sec); IB(762,53 ±46,02mmHg/sec); INC(412,35 ±84,36mmHg/sec) p<0,005. A relação do coeficiente angular logarítmico foi: C(0,108± 0,02); IC(0,159± 0,038); IB(0,114 ±0,016); INC(0,175± 0,038) p<0,05. CONCLUSÃO: No modelo experimental estudado o grupo isquêmico protegido pela cardioplegia sanguínea apresentou melhor função ventricular que os grupos protegidos por cardioplegia cristalóide e não protegido.

Treating metabolic impairment and myocardial stunning with phosphodiesterase inhibitor type III, milrinone, administered prior to coronary artery occlusion in the presence of calcium channel blockade in pigs.

This study examined milrinone effects on ischaemic myocardial metabolism and function with calcium blockade. We studied 15 pigs in 3 groups: group C received no drugs; group D received diltiazem 5 mg bolus followed by infusion; group D+M received diltiazem and milrinone (50microg/Kg). The left anterior descending (LAD) artery was then occluded for 15 minutes. Left ventricular (LV) function data obtained included rate, pressures, output, Emax, and dP/dT. Blood lactate was obtained from the LAD and circumflex vessels at baseline, end of occlusion, early (15 min) and late (1 hour) reperfusion. In group D+M, less depression of LV function occurred during ischaemia and early reperfusion. Lactate extraction in the LAD region was less negative in D+M group than in the group without milrinone during ischaemia and late reperfusion. We conclude the preemptive administration of milrinone prior to ischaemia added to calcium blockade improved myocardialfunction and ischaemic metabolic effects.

Terapia da insuficiência cardíaca avançada ajustada por objetivos hemodinâmicos obtidos pela monitorização invasiva / Advanced heart failure therapy adapted to hemodynamic objectives acquired from invasive hemodynamic monitoring

OBJETIVO: Avaliar o tratamento da insuficiência cardíaca (IC) avançada em relação à redução das pressões de enchimento ventricular, com a utilização de doses maiores de vasodilatadores, através da monitorização hemodinâmica invasiva. MÉTODOS: Foram estudados 19 pacientes com IC avançada, nos quais foi instalado o cateter de Swan-Ganz para guiar a administração de diurético intravenoso (IV) e nitroprussiato de sódio, com o objetivo de se reduzir de forma significativa as pressões de enchimento ventricular. Depois de alcançado esse objetivo ou 48 horas, foram introduzidas drogas orais até serem retirados os fármacos venosos, mantendo o benefício hemodinâmico. RESULTADOS: Dos 19 pacientes estudados, 16 (84 por cento) eram do sexo masculino. A idade média foi de 66 ± 11,4 anos; a fração de ejeção média foi de 26 ± 6,3 por cento; 2 pacientes (10,5 por cento) apresentavam classe funcional (CF) III e 17 (89,5 por cento), CF IV. Houve queda da pressão de oclusão da artéria pulmonar de 23 ± 11,50 mmHg para 16 ± 4,05 mmHg (p=0,008), do índice de resistência vascular sistêmica de 3.023 ± 1.153,71 dynes/s/cm-5/m² para 1.834 ± 719,34 dynes/s/cm-5/m² (p=0,0001) e aumento do índice cardíaco de 2,1 ± 0,56 l/min/m² para 2,8 ± 0,73 l/min/m² (p=0,0003). Um subgrupo com hipovolemia foi identificado. CONCLUSÃO: Foi possível reduzir as pressões de enchimento ventricular para valores significativamente menores, obtendo melhora significativa do índice cardíaco, do índice de resistência vascular sistêmica e da pressão média da artéria pulmonar, utilizando-se doses significativamente maiores de vasodilatadores.

Estudio de los extractos de Magnolia grandiflora sobre el músculo cardíaco de cobayo / Study of Magnolia Grandiflora extracts in guinea pigs cardiac muscle

Se evaluó farmacológicamente los extractos de diversas variedades de Magnolia grandiflora sobre el músculo cardíaco. Se recolectó en el período de marzo a julio hojas y flores de Magnolia grandiflora nativa del Instituto Nacional de Cardiología "Ignacio Chávez", de la zona norte, poniente y oriente del Distrito Federal, de los estados de Puebla, Colima y Chiapas. Éstas se procesaron por separado y los extractos se obtuvieron por maceración con una mezcla de etanol-agua (1:3 v/v) a 4°C durante dos semanas. El análisis cualitativo se realizó por cromatografía en capa fina, columna y de líquidos de alta resolución (CLAR). El análisis funcional y molecular se efectuó por reactividad química específica y resonancia magnética protónica (RMN ¹H). La evaluación farmacológica se realizó en corazones aislados de cobayo macho. Los extractos, fracciones y compuestos se administraron en bolos seriados bajo un estudio de curvas dosis-respuesta gradual en donde se midió la presión intraventricular izquierda y la presión de perfusión coronaria, evaluando así el efecto inotrópico positivo y vasodilatador de los extractos de Magnolia grandiflora. Se identificó y aisló vulgarenol y 2-p-hidroxifenil-2-OH-etilamina, por lo que los resultados sugieren que su efecto vasodilatador e inotrópico positivo, se deben a la presencia de estas sustancias, las cuales se complementan con magnograndiólido y tiramina.

Several extracts from diverse Magnolia grandiflora varieties were pharmacological evaluated in the cardiac muscle. From March to July, flowers and leaves from Magnolia grandiflora, native from the National Institute of Cardiology "Ignacio Chávez", from north, west, and orient zones from Mexico City, and from Puebla, Colima and Chiapas states were collected. They were separately processed and the extracts were obtained by maceration with ethanol-water (1:3 v/v) at 4°C during two weeks. Qualitative analysis was accomplished with thin-layer, column and high-performance liquid chromatographies (HPLC). Functional and molecular analysis was made by specific chemical reactivity and by protonic magnetic resonance (RMN ¹H). Pharmacological evaluation was completed in isolated and perfused male guinea pigs hearts. Extracts, fractions, and compounds were administrated by serial bolus in a gradual dose-response curves study in which left intraventricular pressure and coronary perfusion pressure were recorded, evaluating by such the positive inotropic and vasodilator effects of Magnolia grandifloraextracts. Vulgarenol and 2-p-hydroxyphenyl-2-hydroxy-ethylamine were isolated and identified, and the obtained results suggest that its positive inotropic and vasodilator effects are owed to these substances, being complemented by magnograndiolide and tyramine.