ABC | Volume 115, Nº1, July 2020

Original Article Oliveira-Junior et al Effects of losartan in obesity Arq Bras Cardiol. 2020; 115(1):17-28 Based on using a similar intervention to this study, Vileigas et al. 16 also found unchanged myocardial function in papillary muscle preparation at baseline and after isoproterenol addition. Regarding the PPP assessment, obesity promoted myocardialdysfunction, most probably due to changes in intracellular Ca 2+ handling. The 60s maneuver reduced DT, +dT/dt and -dT/dt values in myocardium of obese rats, as in Figure 3. The results agree with previous studies showing lower contractile response in obese Zucker rats after 60s of PPP 35 . As -dT/dt is influenced by the frequency of calcium ions absorption into the sarcoplasmic reticulum, 7 the lower Ca 2+ recapture shown by -dT/dt in obese rats suggests that SERCA2 protein activity was reduced. Decreasing -dT/dt with high cytosolic Ca 2+ concentrations suggests that activation of SERCA2 from Ca 2+ / calmodulin-dependent protein kinase may be shortened by obesity. Important reduction in DT of obese rats could result not only fromCa 2+ reduction in the sarcoplasmic reticulum, but also from a lower Ca 2+ release through the Rianodine receptors. Figure 2 – Functional papillary muscle assessment according to extracellular calcium concentration (1.0-2.5 mM). Results expressed regarding the baseline with extracellular [Ca 2+ ] equal to 0.5 mM value (mean±SD); (A) DT: maximum developed tension; (B) +dT/dt: maximum positive DT change; (C) -dT/dt, maximum DT decrease. CO: Control group; CL: Control Losartan group; OB: Obese group; OL: Obese Losartan group. Group’s effect: † p<0.05 compared to OB; ‡ p<0.05 compared to CL. Calcium’s Effect: §, p<0.05 compared to 1.0 mM; ¶, p<0.05 compared to 1.5 mM; Two-Way RMANOVA and Bonferroni Test. 23