Acute effect of thymoquinone on action potential and ionic currents of rat cardiac myocytes.

Abstract

This study aims to investigate the acute effects of thymoquinone (TQ) which has been suggested to be a cardioprotective agent, on ventricular myocytes. Freshly isolated rat ventricular myocytes were exposed to TQ and using standard whole-cell patch-clamp technique action potential (AP), sodium current (INa), L-type calcium current (ICaL) and transient outward potassium current (Ito) were measured. TQ prolonged the duration of AP and decreased the peak value compared to that of control myocytes. Consistently, it inhibited INa in a concentration-dependent manner and shifted the channel kinetics to more hyperpolarized voltages. Besides, TQ not only inhibited Ito and ICaL but also significantly attenuated the isoproterenol-induced increase in ICaL. The effect of TQ on cardiomyocytes has been demonstrated for the first time. TQ changes AP morphology along with ionic currents and alleviates β-adrenergic response in adult ventricular myocytes. These results indicate that TQ may be considered as a therapeutic agent in cases such as diabetic cardiomyopathy and cardiac hypertrophy, wherein the β-adrenergic system is over-activated (Tab. 2, Fig. 6, Ref. 30).