The regulation of the small-conductance calcium-activated potassium current and the mechanisms of sex dimorphism in J wave syndrome.

Apamin-sensitive small-conductance calcium-activated potassium (SK) current (I) plays an important role in cardiac repolarization under a variety of physiological and pathological conditions. The regulation of cardiac I relies on SK channel expression, intracellular Ca, and interaction between SK channel and intracellular Ca. I activation participates in multiple types of arrhythmias, including atrial fibrillation, ventricular tachyarrhythmias, and automaticity and conduction abnormality. Recently, sex dimorphisms in autonomic control have been noticed in I activation, resulting in sex-differentiated action potential morphology and arrhythmogenesis. This review provides an update on the Ca-dependent regulation of cardiac I and the role of I on arrhythmias, with a special focus on sex differences in I activation. We propose that sex dimorphism in autonomic control of I may play a role in J wave syndrome.