Hyper- and Hypothyroidism Affect Myocardial Connexin-43 Expression and Susceptibility of the Rat Heart to Malignant Arrhythmias

We aimed to explore relationship between myocardial electrical coupling protein connexin-43 (Cx43) and susceptibility of rats with altered thyroid status to malignant arrhythmias and to examine possible beneficial effect of red palm oil (RPO). We used as experimental model euthyroid (EU), hypothyroid (HY) and hyperthyroid (TH) rats, which were fed RPO (100µl/100g b.w./day) for 6 weeks. Left ventricular tissue was taken for determination of mRNA and protein expression of Cx43 and PKCe. Sustained ventricular fibrillation (sVF) induction was estimated using isolated perfused heart. Results showed that the threshold for sVF was significantly decreased in the TH, in which Cx43 and PKCe expression was down-regulated in comparison with the EU. On the contrary, sustained VF was not induced even by the highest stimulus strength in the HY, in which Cx43 and PKCe expression was up-regulated. RPO intake partly, although significantly, increased VF threshold in TH as well as Cx43 and PKCe proteins expression. We conclude that there is an inverse relationship between myocardial Cx43 expression and heart susceptibility of rats with altered thyroid status to VF.