ABC | Volume 111, Nº2, August 2018

Original Article Rodrigues et al Physical exercise and calcium regulation Arq Bras Cardiol. 2018; 111(2):172-179 Table 1 – Body weight and ventricular weight in the study groups SN (n = 8) TN (n = 8) SH (n = 8) TH (n = 8) p-value BW (g) 411.30 ± 21.51 447.10 ± 43.94 350.60 ± 21.97* & 338.90 ± 30.67 *& 0.001 VW (g) 1.62 ± 0.20 1.49 ± 0.25 1.47 ± 0.17 1.66 ± 0.23 0.954 LVW (g) 1.12 ± 0.13 1.08 ± 0.13 1.18 ± 0.14 1.25 ± 0.15 0.265 VW/BW (mg/g) 3.97 ± 0.62 3.46 ± 0.47 4.19 ± 0.45 4.93 ± 0.80 *& 0.000 LVW/BW (mg/g) 2.75 ± 0.42 2.42 ± 0.23 3.39 ± 0.39 *& 3.72 ± 0.48 *& 0.000 SN: sedentary normotensive; TN: trained normotensive; SH: sedentary hypertensive; TH: trained hypertensive; VW: ventricular weight; LVW: left ventricular weight; n: number of animals; * compared with SN; & compared with TN (p < 0.05). on this parameter in hypertensive animals. Longer time to a 50% decay of [Ca 2+ ] i was observed in TN than SN group. In hypertensive animals, however, this parameter was decreased after physical training (p < 0.05). Although the physical training had no effect on mir-214 expression in normotensive animals (Figure 5), increased expression was found in TH as compared with SH and the other groups. Discussion In the present study, the authors evaluated the effects of physical activity on contractility and intracellular Ca 2+ transients in myocytes and miR-214 expression in the left ventricle in hypertensive rats. The results showed that the aerobic training not only reduced SAP in hypertensive animals, but also increased the amplitude of miR-214. No effect on LV myocyte contractility was observed. The efficacy of the physical training applied in the study groups was confirmed by the higher physical capacity, indicated by the TTE, in trained animals as compared with controls. Such increase in physical capacity in response to aerobic training has been previously demonstrated. 10,17,18 More importantly, physical training reduced SAP in hypertensive animals, and such effect is well established in the literature. 11,19 Regarding LV cardiomyocyte contractility, although a reduction in the cell relaxation time in response to physical training was observed in normotensive animals, in SHR, cell contractility of trained animals was not different than that in sedentary animals. Although cardiomyocyte contractility in SHR was not affected by exercise, higher amplitude and shorter 50% decay time of intracellular Ca 2+ transient levels were seen in trained animals as compared with sedentary controls. This suggests higher availability of Ca 2+ in the cytosol and faster removal of calcium from the cytosol, which in turn brings about relaxation. 20 These findings corroborate those of another study, 21 that showed increased expression of SERCA2a, which is the main determinant of Ca 2+ removal from the cytosol into sarcoplasmic reticulum. 20 With respect to miR-214, which antagonizes the effects of SERCA2a, our results contradict existing data in the literature, since the physical exercise program increased the expression of this microRNA in the left ventricle of hypertensive animals. We expected that aerobic training would reduce the expression of miR-214, which would justify de shorter time to 50% of decay in intracellular concentration of Ca 2+ transients in LV cardiomyocytes of SHR due to an expected increase in SERCA2a expression. Although SERCA2a expression in the left ventricle was not evaluated in the present study, it was previously demonstrated 14 that the left ventricle of normotensive rats subjected to resistance training showed Figure 2 – Systolic arterial pressure (SAP) in normotensive animals and hypertensive animals. (A) SAP pre-training vs. post-training). (B) Final SAP of the groups. SN: sedentary normotensive; TN: trained normotensive; SH: sedentary hypertensive; TH: trained hypertensive. Data are expressed as mean ± SD of 8 animals in each group. * compared with TN (pre) (A) SN (B); & compared with TN (post) (A) TN (B); # compared with TH (pre) (A) SN (B); * compared with TH-post (A) TH (B) (p < 0.05). 200 200 150 150 250 100 100 50 50 0 0 SAP (mmHg) SAP (mmHg) TN (pre) TN (post) TH (pre) TH (post) NS TN HS TH *&+ *”&+ *&# *”&# A B 175