Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 61 10 2024 06 01 607 613 Razieh Mohammad Jafari Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran Dlshad Mohammed Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Seyed Mohammad Tavangar Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Golnar Eftekhari Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Maryam Shokrian Zeini Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. AND Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Arash Khodadoostan School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Ahmad Reza Dehpour Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. AND Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Farahnaz Jazaeri Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran 2024 02 21 2024 02 24 In liver cirrhosis, there is low T3 syndrome associated with a decrease in total triiodothyronine (T3) and free T3 concentrations and cirrhotic cardiomyopathy (CCM) with chronotropic incompetence. Thus, we aimed to investigate the effects of eliminating T3 and thyroxine (T4) deficiencies on cardiac chronotropic dysfunction. Bile duct ligation (BDL) was used to induce cirrhosis in male Wistar rats. The chronotropic responses were studied through the Power Lab system in sham/saline, sham/T3T4, BDL/saline, and BDL/T3T4 groups. The serum T3 and T4, and T3 resin uptake (T3RU) levels were assessed. The atrial T3 receptor expression was investigated through a real-time polymerase chain reaction (Real-time PCR). The chronotropic responses were decreased in the BDL/saline group and raised in the BDL/T3T4 group. The serum T3 levels decreased in the BDL/saline group compared to sham group, but increased in the BDL/T3T4 group compared to the BDL/saline group. The serum T4 level increased in the BDL/saline and decreased in the BDL/T3T4 group. The serum T3RU level decreased in the BDL/saline and increased in the BDL/T3T4 group. The T3 receptor expression in atria increased in the BDL/saline group, nonetheless, it did not change in the BDL/T3T4 group compared to the sham/saline and the BDL/saline groups. T3T4 treatment did not increase the chronotropic response in the control group but the treatment improved the chronotropic hyporesponsiveness, and serum T4 and T3 RU abnormalities in cirrhosis, however, it is not related to the atrial T3 receptor expression. https://acta.tums.ac.ir/index.php/acta/article/view/10973 https://acta.tums.ac.ir/index.php/acta/article/download/10973/5848