As one important constituent extracted from a
traditional Chinese medicine, Uncaria Rhynchophylla Miq Jacks,
isorhynchophylline has been used to treat
hypertension,
epilepsy,
headache, and other illnesses. Whether
isorhynchophylline protects hearts against
cardiac arrhythmias is still incompletely investigated. This study was therefore aimed to examine the preventive effects of
isorhynchophylline on heart arrhythmias in guinea pigs and rats and then explore their electrophysiological mechanisms. In vivo,
ouabain and
calcium chloride were used to establish experimental arrhythmic models in guinea pigs and rats. In vitro, the whole-cell patch-lamp technique was used to study the effect of
isorhynchophylline on action potential duration and
calcium channels in acutely isolated guinea pig and rat cardiomyocytes. The dose of
ouabain required to induce
cardiac arrhythmias was much larger in guinea pigs administered with
isorhynchophylline. Additionally, the onset time of
cardiac arrhythmias induced by
calcium chloride was prolonged, and the duration was shortened in rats pretreated with
isorhynchophylline. The further study showed that
isorhynchophylline could significantly decrease action potential duration and inhibit
calcium currents in isolated guinea pig and rat cardiomyocytes in a dose-dependent manner. In summary,
isorhynchophylline played a remarkably preventive role in
cardiac arrhythmias through the inhibition of
calcium currents in rats and guinea pigs.