Cardiac Activity Assessed in vivo and in Vitro in Rats Treated with Propiltiouracil (PTU)

Thyroid hormones interfere with cardiovascular functions causing morphofunctional changes in cardiomyocytes, evidenced by electrophysiological activities and hemodynamics. This study examined the implications of hypothyroidism on cardiac electrical activity in Wistar rats under experimental conditions in vivo and in vitro. It was approved by the animal ethics committee (CEUA-University of Gurupi-TO, Brazil), using 20 rats (male and / or female), randomly subdivided into 10 control rats (treated with water + aspartame) and 10 experimental rats (treated with water + aspartame + PTU) for 4 weeks. On the 31st day, in thestudies in vivo, the electrocardiographic tracings (ECG DL 660 Delta Life) were obtained with the anesthetized animals and, in the Langendorff preparation, the hearts were isolated and perfused in a chamber with electrodes (Ag / AgCl) connected to the ECG and recorded cardiac electrophysiological activity. In both protocols the analyzed variables were: heart rate (BPM), amplitudes (mV) of P, QRS and T deflections and intervals (ms) PR, QRS and QT. The results obtained were bradycardia, prolongation of the PR interval, QRS and QT interval in bothprotocols in vivoin and in vitro rats treated with Propylthiouracil (PTU). In theexperiment in vitro there was a reduction of P wave amplitude and no significant change in ventricular contractility compared to the control group. It is concluded that the deficit of thyroid hormones alters the functions of cardiac chronotropism and dromotropism evidenced by bradycardia and stretching of PR, QT and QRS intervals.