IJCS | Volume 31, Nº6, November / December 2018

591 Figure 4 - Distribution of volume densities of cytoplasmic organelles and by interstitium between the UC, TC, UI, and TI groups. Volumetric density of granules (Vv[gr]), mitochondria (Vv[mit]), myofibrils (Vv[myofib]), Golgi complex (Vv[golgi]), interstitium (Vv[int]), and others (Vv[others]). Ferraboli et al. Effect of mild aerobic exercise in Chagas’disease Int J Cardiovasc Sci. 2018;31(6)585-593 Original Article concentrated in the nuclear envelope and dispersed in the nucleus. A reduced number of granules was observed, with a predominance of small granules dispersed in the cytoplasm and around the Golgi apparatus and mitochondria, and in the peripheral region of the cytoplasmic membrane. Conclusion Our results suggest that physical exercise (light) performed by chagasic animals is beneficial to the heart, promoting rehabilitation of sequelae caused by myocyte injuries during parasitemia throughout the acute phase of the disease. This benefit was likely due to increased heart rate, which stimulates the production of electron- dense atrial granules and ANP in response, providing greater blood volume and pressure of the atrial walls, and consequently increased secretion of ANP. Author contributions Conception and design of the research: Ferraboli R, Ornelas EM, Fonseca FLA, Cardoso CG, Maifrino LBM. Acquisition of data: Ferraboli R, Ornelas EM, Fonseca FLA. Analysis and interpretation of the data: Ferraboli R, Ornelas EM, Fonseca FLA, Veiga GL, Marques MR, Maifrino LBM. Statistical analysis: Ferraboli R, Fonseca FLA. Obtaining financing: Maifrino LBM. Writing of the manuscript: Ferraboli R, Veiga GL, Cardoso CG, Maifrino LBM. Critical revision of the manuscript for intellectual