Existence of a delayed rectifier K+ current in the membrane of human embryonic stem cel

Introduction: Human embryonic stem cells (hESCs) are pluripotent cells that can proliferate and differentiate to many cell types. Their electrophysiological properties have not yet been chracterzed. In this study, the passive properties (such as resting membrane potential, input resistance and capacitance) and the contribution of delayed rectifier K+ channel currents to the membrane conductance of hESCs was investigated. Methods: hESC (Royan H6 line) was used in this study. Cells were cultured with feeder free culture method. To study the electrophysiological properties of these cells, we used whole cell patch clamp technique in a voltage clamp mode. Ionic currents were recorded by stimulating the cells with depolarizing steps from -90 mV to +50 mV. For pharmacological determination of these currents, potassium channel blockers such as tetraethyl ammonium (TEA a delayed rectifier K+ channel blocker) and 4-aminopyridine (4-AP as an A-type K+ channel blocker) were used. Results: The resting membrane potential of hESCs was -8.66± 0.87 mV, the input resistance was 11.943 ± 0.23 MΩ and the membrane capacitance was 1.46 ± 0.55 nF. In voltage clamp experiments, some outward currents were recorded in hESCs that were progressively increased with positive voltages. These outward currents were inhibited by TEA but not 4-AP. These channels did not show inactivation and their current were recorded from -60 mV. The mean conductance of these channels was 11.81 ± 0.45 pS at -60 mV and 141.4 ± 10.97 pS at +50 mV. There were no inward currents in hESCc.