Vieira Fabricio Furtado, Olivoto Robson Ruiz, Silva Priscyla Oliveira da, Francisco Julio Cesar, Fogaça Rosalvo Tadeu Hochmuller
Laboratório de Fisiologia da Contração Muscular, Universidade Federal do Paraná, Brazil.
Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, PR, Brazil.
Arq Bras Cardiol. 2016 Dec;107(6):542-549. doi: 10.5935/abc.20160179.
Hyperthyroidism is currently recognized to affect the cardiovascular system, leading to a series of molecular and functional changes. However, little is known about the functional influence of hyperthyroidism in the regulation of cytoplasmic calcium and on the sodium/calcium exchanger (NCX) in the cardiac muscle.
To evaluate the functional changes in papillary muscles isolated from animals with induced hyperthyroidism.
We divided 36 Wistar rats into a group of controls and another of animals with hyperthyroidism induced by intraperitoneal T3 injection. We measured in the animals' papillary muscles the maximum contraction force, speed of contraction (+df/dt) and relaxation (-df/dt), contraction and relaxation time, contraction force at different concentrations of extracellular sodium, post-rest potentiation (PRP), and contraction force induced by caffeine.
In hyperthyroid animals, we observed decreased PRP at all rest times (p < 0.05), increased +df/dt and -df/dt (p < 0.001), low positive inotropic response to decreased concentration of extracellular sodium (p < 0.001), reduction of the maximum force in caffeine-induced contraction (p < 0.003), and decreased total contraction time (p < 0.001). The maximal contraction force did not differ significantly between groups (p = 0.973).
We hypothesize that the changes observed are likely due to a decrease in calcium content in the sarcoplasmic reticulum, caused by calcium leakage, decreased expression of NCX, and increased expression of a-MHC and SERCA2.
目前已认识到甲状腺功能亢进会影响心血管系统，导致一系列分子和功能变化。然而，关于甲状腺功能亢进对细胞质钙调节以及心肌中钠/钙交换器（NCX）的功能影响知之甚少。
评估从诱导甲状腺功能亢进的动物分离出的乳头肌的功能变化。
我们将36只Wistar大鼠分为对照组和腹腔注射T3诱导甲状腺功能亢进的动物组。我们测量了动物乳头肌的最大收缩力、收缩速度（+df/dt）和舒张速度（-df/dt）、收缩和舒张时间、不同细胞外钠浓度下的收缩力、静息后增强（PRP）以及咖啡因诱导的收缩力。
在甲状腺功能亢进的动物中，我们观察到所有静息时间的PRP均降低（p < 0.05），+df/dt和-df/dt增加（p < 0.001），对细胞外钠浓度降低的正性肌力反应较低（p < 0.001），咖啡因诱导收缩的最大力降低（p < 0.003），总收缩时间缩短（p < 0.001）。两组之间的最大收缩力无显著差异（p = 0.973）。
我们推测观察到的变化可能是由于肌浆网钙含量减少，这是由钙泄漏、NCX表达降低以及α-MHC和SERCA2表达增加引起的。
