RESUMEN

We previously showed that digitoxin prolongs the survival of rats with heart failure due to myocardial infarction (MI). In this study, we evaluated the effect of digitoxin on myocardial structure, ventricular function, and proteins involved in calcium kinetics. Seventy-two rats with MI >35% of the left ventricle were randomly assigned to 4 treatment groups: sham (n = 15), digitoxin (n = 11), infarction (n = 20), and infarction + digitoxin (n = 26). The rats were assessed 120 days after surgery by echocardiogram, hemodynamics, papillary muscle mechanics, collagen content, cardiomyocyte nuclear volume, and Western blot analysis of proteins involved in calcium kinetics. Digitoxin was administered via the rat chow. Two-way analysis of variance was used for comparisons. Myocardial infarction caused inotropic impairment, pulmonary congestion, increase of nuclear volume, myocardial collagen, and Na+/Ca2+ exchanger levels, and decreased SERCA2 and phosphorylated phospholamban levels. Treatment with digitoxin showed improvements in cardiac remodeling, inotropism, ventricular performance, pulmonary congestion, collagen accumulation, nuclear volume, and proteins involved in calcium kinetics. In rats with heart failure due to MI, long-term treatment with digitoxin attenuates congestive heart failure, mitigates myocardial remodeling and contractile impairment, and preserves myocardial levels of proteins involved in calcium kinetics.

Asunto(s)

Proteínas de Unión al Calcio/metabolismo , Cardiotónicos/farmacología , Digitoxina/farmacología , Insuficiencia Cardíaca/prevención & control , Hipertrofia Ventricular Izquierda/prevención & control , Contracción Miocárdica/efectos de los fármacos , Infarto del Miocardio/tratamiento farmacológico , Miocardio/metabolismo , Función Ventricular Izquierda/efectos de los fármacos , Remodelación Ventricular/efectos de los fármacos , Animales , Calcio/metabolismo , Señalización del Calcio , Modelos Animales de Enfermedad , Femenino , Insuficiencia Cardíaca/metabolismo , Insuficiencia Cardíaca/patología , Insuficiencia Cardíaca/fisiopatología , Hipertrofia Ventricular Izquierda/metabolismo , Hipertrofia Ventricular Izquierda/patología , Cinética , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Miocardio/patología , Ratas Wistar

RESUMEN

The present study aimed to analyze the effects of reperfusion of a distant coronary artery on cardiac function, the ultrastructure, and the molecular environment of the remote myocardium immediately after the completion of myocardial regional necrosis: delayed reperfusion (DR). Additionally, the effects of prior exercise on the outcomes of DR were investigated. Female rats with permanent occlusion or delayed reperfusion were randomly assigned to an exercise (swimming, 1 h/day, 5 days/week for 8 weeks) or sedentary protocol. Thus, the study included the following four groups: sedentary permanent occlusion, exercise permanent occlusion, sedentary delayed reperfusion, and exercise delayed reperfusion. The descending coronary artery was occluded for 1 h. Reperfusion was confirmed by contrast echocardiography, and the rats were observed for 4 weeks. Permanent occlusion and DR caused similar myocardial infarction sizes among the four groups. Interestingly, exercise significantly decreased the mortality rate. Delayed reperfusion resulted in significant benefits, including enhanced hemodynamics and papillary muscle contraction, as well as reduced apoptosis and collagen content. Protein calcium kinetics did not change. Meanwhile, developed tension and the Frank-Starling mechanism were enhanced, suggesting that calcium sensitivity was intensified in myofilaments. Remarkable remote myocardial benefits occurred after distant DR, and prior exercise intensified cardiac recovery. Our findings provide valuable information about DR. Our data might explain the better clinical outcomes in recent studies showing that late reperfusion could improve heart failure in patients with myocardial infarction. In conclusion, DR has remote myocardial benefits, including inotropism enhancement, pulmonary congestion reduction, and collagen and apoptosis attenuation, which are enhanced by prior exercise.