Role of ATP-dependent K(+) channels in the electrical excitability of early embryonic stem cell-derived cardiomyocytes.
Single, murine embryonic stem cell-derived early stage cardiomyocytes dissociated from embryoid bodies expressed two inward rectifier K(+) channels, I(K1) and the ATP dependent K(+) current. I(K1) exhibited low density in early stage cardiomyocytes, but increased significantly in late stage cells. In contrast, the ATP dependent K(+) current was expressed at similar densities in early and late stage cardiomyocytes. This current was found to be involved in the determination of the membrane potential, since glibenclamide depolarized early cardiomyocytes and exerted a positive chronotropic effect. Some cardiomyocytes displayed a bursting behavior of action potentials, characterized by alternating periods with and without action potentials. During the phases without action potentials, the membrane potential was hyperpolarized, indicating the involvement of K(+) channels in the generation of this bursting behavior. Extracellular recording techniques were applied to spontaneously contracting areas of whole embryoid bodies. In 20% of these bursting behavior similar to that seen in the single cells was observed. In regularly beating embryoid bodies, bursting could be induced by reduction of substrates from the extracellular medium as well as by superfusion with the positive chronotropic agents Bay K 8644 or isoproterenol. Perfusion with substrate-reduced medium induced bursting behavior after a short latency, isoproterenol and Bay K 8644 resulted in a positive chronotropic response followed by bursting behavior with longer latencies. The spontaneous bursting was blocked by glibenclamide. These experimental results suggest that intermittent activation of ATP dependent K(+) channels underlies the bursting behavior observed in single cardiomyocytes and in the whole embryoid body. Conditions of metabolic stress lead to the rhythmic suppression of action potential generation. Our data indicate that ATP dependent K(+) channels play a prominent role in the cellular excitability of early cardiomyocytes.
Gryshchenko
O
O
Zentrum Physiologie und Pathophysiologie der Universität zu Köln, Institut für Neurophysiologie, Robert-Koch-Str. 39, D-50931 Köln, Germany.
Fischer
I R
IR
Dittrich
M
M
Viatchenko-Karpinski
S
S
Soest
J
J
Böhm-Pinger
M M
MM
Igelmund
P
P
Fleischmann
B K
BK
Hescheler
J
J
D019297:2,4-Dinitrophenol / Q000494:pharmacology; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D018528:ATP-Binding Cassette Transporters; D000200:Action Potentials / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D018999:Charybdotoxin / Q000494:pharmacology; D019806:Cromakalim / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D054086:KATP Channels; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009200:Myocardial Contraction; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D009940:Organoids; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D013234:Stem Cells / Q000166:cytology; D019284:Thapsigargin / Q000494:pharmacology
D018528:ATP-Binding Cassette Transporters; D002120:Calcium Channel Agonists; D002316:Cardiotonic Agents; D004791:Enzyme Inhibitors; D054086:KATP Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C092520:uK-ATP-1 potassium channel; D019806:Cromakalim; D018999:Charybdotoxin; D019284:Thapsigargin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000255:Adenosine Triphosphate; D007545:Isoproterenol; D019297:2,4-Dinitrophenol; D005905:Glyburide