Influence of aerobic physical training on cardiac remodeling of spontaneously hypertensive rats treated with dexamethasone

Abstract

Heart failure (HF) is one of the most deadly cardiovascular diseases in Brazil. Cardiac hypertrophy, increased fibrosis and capillary density reduction are implicated in its development. Spontaneously hypertensive rats (SHR), throughout their life, develop cardiac hypertrophy due to arterial hypertension (HA) evolution. However, little is known about dexamethasone-effects (DEX) in these animals, since DEX-chronic treatment provokes HA and cardiac hypertrophy. On the other hand, aerobic physical training (T) has been used as non-pharmacological treatment of HA and one of its mechanisms is cardiac remodeling alterations. The hypothesis of this study is that DEX may promote a highest increase in blood pressure (BP) and worse the cardiac remodeling process in SHR. On the other hand, T may be able to mitigate these deleterious effects of DEX. Therefore, the objective of the present study will be to investigate whether DEX-treatment worsens cardiac remodeling process in SHR and if T attenuates this response. For this, SHR will perform 8-weeks of T on the treadmill (60% of the maximum capacity, 5 days per week, 1 hour per day) or remain sedentary. Wistar sedentary rats will be used as control. During the following 14 days, after 8 weeks of T, animals will be treated with DEX (50 ¼g / kg of body weight per day, s.c.) or saline. Before and after the experimental protocol, these animals will be submitted to an echocardiogram examination. At the end of the experimental protocol, heart rate (HR) and direct blood pressure (BP) will be measured by carotid artery catheterization and spectral analysis will be performed. After, heart will be removed for capillary density analysis, myocyte diameter, type I and III collagen localization and analysis of protein production. The results will be presented as mean ± standard error of the mean (SEM). One way variance analysis (ANOVA) and Tukey post-hoc, with p <0,05. (AU)