Functional Effects of Hyperthyroidism on Cardiac Papillary Muscle in Rats

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 c...

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Published in:	Arquivos brasileiros de cardiologia Vol. 107; no. 6; pp. 542 - 549
Main Authors:	Vieira, Fabricio Furtado, Olivoto, Robson Ruiz, Silva, Priscyla Oliveira da, Francisco, Julio Cesar, Fogaça, Rosalvo Tadeu Hochmuller
Format:	Journal Article
Language:	English Portuguese
Published:	Brazil Sociedade Brasileira de Cardiologia - SBC 01-12-2016 Sociedade Brasileira de Cardiologia (SBC)
Subjects:	Animals Calcium - analysis Calcium - metabolism CARDIAC & CARDIOVASCULAR SYSTEMS Contração Miocárdica Heart - physiopathology Hipertireoidismo / metabolismo Hormônios Tireóideos Hyperthyroidism - physiopathology Male Miocárdio Muscle Strength - physiology Myocardial Contraction - physiology Organ Size Original Papillary Muscles - physiopathology Random Allocation Ratos Rats, Wistar Reference Values Sodium-Calcium Exchanger - metabolism Time Factors Transducers Myocardial Contraction Contração Miocárdica Miocárdio Thyroid Hormones Rats Myocardium Ratos Hormônios Tireóideos Hyperthyroidism / metabolism Hipertireoidismo / metabolismo
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Summary:	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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0066-782X 1678-4170 1678-4170
DOI:	10.5935/abc.20160179