Sarcoplasmic reticulum Ca2+ release channel ryanodine receptor (RyR2) plays a crucial role in aconitine-induced arrhythmias.

The present study established a model of RyR(2) knockdown cardiomyocytes and elucidated the role of RyR(2) in aconitine-induced arrhythmia. Cardiomyocytes were obtained from hearts of neonatal Sprague-Dawley rats. siRNAs were used to down-regulate RyR(2) expression. Reduction of RyR(2) expression was documented by RT-PCR, western blot, and immunofluorescence. Ca(2+) signals were investigated by measuring the relative intracellular Ca(2+) concentration, spontaneous Ca(2+) oscillations, caffeine-induced Ca(2+) release, and L-type Ca(2+) currents. In normal cardiomyocytes, steady and periodic spontaneous Ca(2+) oscillations were observed, and the baseline Ca(2+) remained at the low level. Exposure to 3 microM aconitine increased the frequency and decreased the amplitude of Ca(2+) oscillations; the baseline Ca(2+) and the level of caffeine-induced Ca(2+) release were increased but the L-type Ca(2+) currents were inhibited after application of 3 microM aconitine for 5 min. In RyR(2) knockdown cardiomyocytes, the steady and periodic spontaneous Ca(2+) oscillations almost disappeared, but were re-induced by aconitine without affecting the baseline Ca(2+) level; the level of caffeine-induced Ca(2+) release was increased but L-type Ca(2+) currents were inhibited. Alterations of RyR(2) are important consequences of aconitine-stimulation and activation of RyR(2) appear to have a direct relationship with aconitine-induced arrhythmias. The present study demonstrates a potential method for preventing aconitine-induced arrhythmias by inhibiting Ca(2+) leakage through the sarcoplasmic reticulum RyR(2) channel.