Establishment of a new arrhythmia model in SD rats induced by isoproterenol

The main purpose of this study was to establish an ideal arrhythmia model using isoproterenol and explore its mechanism.

Fifty healthy male SD rats were randomly divided into the following groups: control (CON), subcutaneous injection (SC; 5 mg/kg ISO for 2 consecutive days), intraperitoneal injection (IP; ISO 5 mg/kg for 2 consecutive days), 2 + 1 (5 mg/kg ISO by SC for 2 consecutive days and then 3 mg/kg ISO by IP for 1 day), and 6 + 1 (5 mg/kg ISO by SC for 6 consecutive days and then 3 mg/kg ISO by IP for 1 day). Electrocardiograms (ECGs) were recorded using a BL-420F system, and the pathological changes in myocardial tissue were observed by HE and Masson staining. The serum cTnI, TNF-α, IL-6, and IL-1β levels were detected by ELISA, and serum CK, LDH and oxidative stress-related indicators were detected with an automatic biochemical analyser.

The cardiomyocytes of the rats belonging to the CON group were normal, whereas those of the rats in the other groups, particularly the 6 + 1 group, showed signs of disorder, unclear borders, and lysis and necrosis. The incidence of arrhythmia, arrhythmia score, and levels of serum myocardial enzymes, troponin, and some inflammatory factors were higher in the 2 + 1 and 6 + 1 groups than in the single injection group (p < 0.01 or p < 0.05). The indicator levels found for the 6 + 1 group were generally higher than those found for the 2 + 1 group (p < 0.01), and the 6 + 1 group exhibited a lower SOD level and higher MDA and NO levels compared with the CON group (p < 0.01 or p < 0.05).

The combined mode of ISO injection (SC with IP) was more likely to induce arrhythmia than a single ISO injection. The "6 + 1" method of ISO injection can establish a more stable arrhythmia model and cardiomyocyte damage induced by oxidative stress and inflammation was an important mechanism.