Abstract Thyroid hormones increase cardiac contractility due to their effect on the Ca 2+ homeostasis in cardiomyocytes. Type 2 deiodinase (D2), which provides local synthesis of T 3 from T 4 , is essential for the adaptation of skeletal muscles to aerobic exercise; however, its role in the myocardium has not been explored. The aim of this study was to assess the effect of wheel training on the expression of genes that regulate the heart contractility and to explore the relationship of their mRNA content in the myocardium with indicators of systemic and local T 3 production. Male Wistar rats were housed in cages with running wheels for eight weeks; the samples of their serum were used to determine hormones by ELISA and muscle tissue to determine mRNA content by reverse transcription quantitative PCR. The training was accompanied by a moderate hypertrophy of the soleus muscle and an increase in its citrate synthase mRNA content. Ventricle mass and the expression levels of αMHC, βMHC, β 1 -adrenoreceptors, Cav 1.2, Serca2, RyR2, and PLB mRNA in trained rats did not differ from respective values in the control groups of rats. Blood content of free T 3 and the expression of D2 mRNA in the left ventricle increased as a result of training; a negative correlation between these indicators was found. The levels of Serca2, Cav 1.2, and RyR2 mRNA positively correlated with the D2 mRNA content in the trained but not in control rats; however, these parameters did not correlate with the free T 3 level in the blood. The observed correlations suggest that myocardium adaptation to aerobic exercise is governed by the effect of locally synthesized T 3 rather than by an increase in its systemic production.

中文翻译：

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自主轮训练诱导大鼠心肌钙稳态调控基因表达的变化：甲状腺激素的作用

摘要 由于甲状腺激素对心肌细胞 Ca 2+ 稳态的影响，甲状腺激素可增加心脏收缩力。2 型脱碘酶 (D2) 可从 T 4 局部合成 T 3 ，对于骨骼肌适应有氧运动至关重要；然而，尚未探索其在心肌中的作用。本研究的目的是评估轮训练对调节心脏收缩力的基因表达的影响，并探讨心肌中这些基因的 mRNA 含量与全身和局部 T 3 产生指标的关系。雄性 Wistar 大鼠被关在带有跑轮的笼子里八周；他们的血清样本通过ELISA测定激素，肌肉组织通过逆转录定量PCR测定mRNA含量。训练伴随着比目鱼肌的适度肥大和柠檬酸合酶 mRNA 含量的增加。训练大鼠的心室质量和αMHC、βMHC、β1-肾上腺素能受体、Cav 1.2、Serca2、RyR2和PLB mRNA的表达水平与大鼠对照组中的各自值没有差异。训练后左心室游离T 3 血含量和D2 mRNA表达增加；发现这些指标之间存在负相关。Serca2、Cav 1.2 和 RyR2 mRNA 的水平与训练大鼠的 D2 mRNA 含量呈正相关，而在对照大鼠中则不然；然而，这些参数与血液中的游离 T 3 水平无关。