Electrophysiological Mechanism of Catestatin Antiarrhythmia: Enhancement of I to , I K, and I K1 and Inhibition of I Ca -L in Rat Ventricular Myocytes.

Background: Cardiovascular disease remains one of the leading causes of death globally. Myocardial ischemia and infarction, in particular, frequently cause disturbances in cardiac electrical activity that can trigger ventricular arrhythmias. We aimed to investigate whether catestatin, an endogenous catecholamine-inhibiting peptide, ameliorates myocardial ischemia-induced ventricular arrhythmias in rats and the underlying ionic mechanisms.
Methods and Results: Adult male Sprague-Dawley rats were randomly divided into control and catestatin groups. Ventricular arrhythmias were induced by ligation of the left anterior descending coronary artery and electrical stimulation. Action potential, transient outward potassium current, delayed rectifier potassium current, inward rectifying potassium current, and L-type calcium current ( I _Ca-L ) of rat ventricular myocytes were recorded using a patch-clamp technique. Catestatin notably reduced ventricular arrhythmia caused by myocardial ischemia/reperfusion and electrical stimulation of rats. In ventricular myocytes, catestatin markedly shortened the action potential duration of ventricular myocytes, which was counteracted by potassium channel antagonists TEACl and 4-AP, and I _Ca-L current channel agonist Bay K8644. In addition, catestatin significantly increased transient outward potassium current, delayed rectifier potassium current, and inward rectifying potassium current density in a concentration-dependent manner. Catestatin accelerated the activation and decelerated the inactivation of the transient outward potassium current channel. Furthermore, catestatin decreased I _Ca-L current density in a concentration-dependent manner. Catestatin also accelerated the inactivation of the I _Ca-L channel and slowed down the recovery of I _Ca-L from inactivation.
Conclusions: Catestatin enhances the activity of transient outward potassium current, delayed rectifier potassium current, and inward rectifying potassium current, while suppressing the I _Ca-L in ventricular myocytes, leading to shortened action potential duration and ultimately reducing the ventricular arrhythmia in rats.