ABC | Volume 110, Nº3, March 2018

Original Article Rodrigues et al Aerobic exercise training in β 1ARKO mice Arq Bras Cardiol. 2018; 110(3):256-262 Table 1 – Body and left ventricular weights WTc (n = 7) WTt (n = 6) β 1 ARKOc (n = 7) β 1 ARKOt (n = 6) Initial BW, g 27.43 ± 2.46 26.50 ± 2.45 33.86 ± 2.46 32.67 ± 2.23 Final BW, g 29.86 ± 2.64* 28.67 ± 2.64* 37.14 ± 2.64* 34.33 ± 2.55* HW, mg 231.00 ± 37.57 226.00 ± 37.48 302.00 ± 37.57 317.00 ± 37.48 LVW, mg 146.00 ± 20.82 141.00 ± 20.82 184.00 ± 20.82 194.00 ± 20.82 HW/BW, mg/g 7.73 ± 0.85 7.86 ± 0.86 8.12 ± 0.85 9.22 ± 0.86 LVW/BW, mg/g 4.89 ± 0.48 4.94 ± 0.49 4.96 ± 0.48 5.66 ± 0.49 Values are means ± SD; WTc: wild-type control; WTt: wild-type trained; β 1 ARKOc: knockout β 1 -ARs control; β 1 ARKOt: knockout β 1 -ARs trained; BW: body weight; HW: heart weight; LVW: left ventricular weight; N: number of animals; *p < 0.05 vs. initial BW within the same group. Statistical differences were determined by paired t test. Figure 1 – Total distance run. Values are means ± SD of 8 mice in each group. *p < 0.05 vs. WTc group; §p < 0.05 vs. WTt group; #p < 0.05 vs. β1ARKOc group. 650 600 550 500 450 400 350 300 250 200 150 0 WTc WTt B1c B1t * * #§ Distance run (m) WT animals. As expected, the final BW of each group was higher, compared to their respective initial BW. The final BW was higher (p < 0.05) in β 1 ARKO ( β 1 ARKOc + β 1 ARKOt), compared to WT mice (WTc + WTt). However, the final BW was not affected (p > 0.05) by the MCAE. Likewise, HW was higher in β 1 ARKO than in WT mice, but no effect of MCAE was observed (p > 0.05). Regarding LVW, β 1 ARKO presented higher values than WT mice; nevertheless, no effect of MCAE was found (p > 0.05). As for the ratios, β 1 ARKO mice presented higher HW to BW ratio than WT mice. However, it was not affected by MCAE (p > 0.05). The LVW to BW ratio was higher in β 1 ARKOmice, compared to WT mice, but there was no effect of MCAE. Figure 1 shows the physical capacity. β 1 ARKO animals ( β 1 ARKOc + β 1 ARKOt) exhibited a longer running distance, compared to WT animals (WTc + WTt). In addition, trained animals presented a longer running distance, compared to their respective controls. The contractile properties of single LV myocytes are presented in Figure 2. β 1 ARKOmyocytes ( β 1 ARKOc+ β 1 ARKOt) had higher shortening amplitude that WT cells (WTc + WTt). The amplitude of shortening in β 1 ARKOt myocytes was higher, compared to β 1 ARKOc and WTt cells; and in WTc cells, compared to WTt cells (Figure 2A). Regarding the contractile time course, β 1 ARKOc myocytes exhibited higher velocity of shortening than WTc cells. In addition, β 1 ARKOt myocytes exhibited higher velocity of shortening than β 1 ARKOc andWTt cells (Figure 2B). As for the velocity of relaxation, β 1 ARKOc myocytes exhibited higher values than WTc cells. Moreover, β 1 ARKOt myocytes exhibited higher velocity of relaxation than β 1 ARKOc and WTt cells (Figure 2C). Discussion In this study, we tested the effects of MCAE on mechanical properties of LV myocytes from β 1 ARKOmice. The main finding was that MCAE increased the amplitude of shortening and velocities of shortening and relaxation in β 1 ARKOmicemyocytes. The initial and final BWs were higher in β 1 ARKO than in WT mice. Similar results have been observed elsewhere. 21 β -AR activation in adipose tissue leads to cyclic adenosine monophosphate (cAMP) production, which activates protein kinase A (PKA) and stimulates lipolysis. Even though β 3 -AR is the predominant receptor in rodent adipose tissue, mice overexpressing β 1 -AR exhibit increased adipocyte lipolytic activity. 22 Therefore, β 1 ARKO mice may have reduced lipolysis, which would influence the amount of body fat and, consequently, BW. 23 Nevertheless, our MCAE did not affect the final BW. Regarding HW, β 1 ARKO mice exhibited heavier hearts and left ventricles than WT mice, as well as higher HW to BW and LVW to BW ratios. Our MCAE, nevertheless, did not modify these cardiac parameters. Exercise-induced cardiac hypertrophy in WT mice has been demonstrated elsewhere; 24-26 nevertheless in β 1 ARKO mice, as far as we know, no data have been reported. 258