(a)
(b)
(c)
Figure 3: (a) Force-frequency relationship of isolated right ventricular papillary muscles. Isometric developed force values are expressed as a fraction of its corresponding value at the basal frequency of 4 Hz and presented as mean ± SEM. Basal; = 8, thyroxin (T4); = 8, propylthiouracil (PTU) + T4; = 10, recovery; = 9. significant change compared to PTU + T4. One-way ANOVA followed by Tukey-Kramer’s post hoc multiple comparison test at all frequencies except the 8 Hz (Kruskal-Wallis analysis). significant change compared to both the group and frequency variation (Friedman nonparametric repeated measures ANOVA followed by Dunn’s post hoc multiple comparison test). (b) β-Adrenergic stimulation of isolated right ventricular papillary muscles. Isometric developed force values following β-adrenergic stimulation are expressed as a fraction of its corresponding value at the basal frequency of 4 Hz before isoproterenol addition and presented as mean ± SEM. (c) Arrhythmic activity at 1 mmol/L of isoproterenol. Basal; = 8, thyroxin (T4); = 7, propylthiouracil (PTU) + T4; = 9, recovery; . significant change compared to T4, and significant change compared to PTU + T4. Significance mark above the error bar represents the group of the upper symbol, while a significance mark on the side reflects the lower. One-way ANOVA followed by Tukey-Kramer’s post hoc multiple comparison test at all isoproterenol concentrations, except the 10−9 and 3 10−9 M (Kruskal-Wallis test followed by Dunn’s post hoc multiple comparison test). significant change compared to both the group and isoproterenol concentration variations (repeated measures ANOVA followed by Tukey-Kramer’s post hoc multiple comparison test).