Effect and mechanism of Irbesartan on occurrence of ventricular arrhythmias in rats with myocardial ischemia through connexin43 (cx43).

OBJECTIVE: To explore the effect and mechanism of angiotensin II receptor blockers - Irbesartan on occurrence of ventricular arrhythmias in rats with myocardial ischemia.

METHODS: Rats with embryonic cardiomyocytes-H9c2 were randomly divided into control group, ischemia group, Irbesartan group and Irbesartan + ischemia group. The cell viability of rats in each group was tested using MTT. Real-time PCR was employed to detect the expression of connexin43 (Cx43) mRNA and western blot to detect the expression of Cx43 and phosphorylated Cx43. SD rats were randomly divided into the sham-operation group (SO), myocardial infarction group (MI), Irbesartan group and MI + Irbesartan group, with 10 rats in each group. HE staining was employed to observe the change in the pathomorphology of left ventricular tissue and TUNEL method to analyze the cell apoptosis in the tissue. The immunofluorescence was adopted to observe the expression and distribution of Cx43 in the left ventricular myocardium and study the change in the expression of Cx43 in the cardiac muscular tissue at mRNA and protein level.

RESULTS: The intervention of Irbesartan in the condition of ischemia indicated the significant decrease in the number of necrotic cells. The expression of Cx43 was significantly decreased under the culture of ischemia (P < 0.05), but in the presence of Irbesartan, the expression of Cx43 was increased compared with the ischemia group (P < 0.01). The results of WB assay showed the similar trend of change at mRNA level. There was the significant difference in the score of ventricular arrhythmia between MI group and SO group (P < 0.01). The incidence of ventricular tachycardia or ventricular fibrillation was significantly increased compared with the one in SO group (P < 0.05). There was the significant difference in the overall score between MI + Irbesartan group and MI group (P < 0.05). The expression of Cx43 in the cardiac muscular tissue in MI group was significantly decreased (P < 0.01 vs SO group). But the expression of Cx43 was increased after the treatment with Irbesartan.

CONCLUSIONS: Irbesartan can inhibit the injury of H9c2 cardiomyocytes and the decreased expression of Cx43 that are induced by the ischemic myocardial infarction. Irbesartan can also improve the reconstruction of Cx43 in rats with ischemic myocardium to inhibit the myocardial infarction-induced arrhythmias.