Functional expression of potassium channels in cardiomyocytes derived from embryonic stem cells

Royan B1 stem cell can be differentiated to specialized cell types including cardiomyocytes. This developmental change is accompanied with expression of various K+ channel types. The aim of this study was to detect functional expression of K+ currents from stem cell stage and one week and two weeks after differentiation into cardiomyocyte. Mouse stem cell derived cardiomyocytes (ES-cardiomyocytes) were isolated to single cell suspension for K+current recording using whole cell patch-clamp technique. The predominant depolarizing current in ES-cardiomyocytes was a tetraethylammonium (TEA) (10 mM) sensitive current which was partially blocked by nifedipine (1 µM) and attenuated by increasing concentration of EGTA (10 mM) in the pipette solution. Pharmacology and electrophysiological properties of this oscillatory sustained current very well matched with characteristics of Ca2+ activated K+ current. In addition there was another kind of sustained outward K+ current which was resistance to TEA but was inhibited by 3,4-diaminopyridine. The characteristic features of this current indicate that this current was due to activation of delayed rectifier K+ channels. RT-PCR study also confirmed expression of these two types of K+ channels in ES-cardiomyocytes. Therefore, present study shows functional expression of two types of K+ ionic current in ES-cardiomyocytes.