Abstract: Objective To investigate the endogenous voltage-gated potassium channels in human embryonic kidney (HEK293) cells. Methods The standard whole-cell recording method was used to record different outward currents in HEK293 cells. And the detailed electrophysiology of these channels were studied. Results No obvious chloride currents were found in native HEK293 cells. No obvious background potassium currents or delayed rectifier potassium currents were recorded either. 4-aminopyridine (4-AP) sensitive potassium currents were found in 59.7% of HEK293 cells. 2 mmol/L 4-AP can completely inhibit this current. The amplitude of this current was (175 112)pA at 40mV. The inactivation curve shows the V1/2 was (-3.5 0.9)mV，with a slope of (6.3 0.8)mV. The inactivation kinetics of this channel was bell-shaped. The recovery time constant of this channel from inactivation was (333.3 33.9)ms. All these data suggest this current is similar to transient outward potassium current (Ito) and this channel is the main endogenous functional channel in HEK293 cells. Conclusion Transient outward potassium current exists in native HEK293 cells, which is a widely used expressing system of different protein including channel protein. So we should be cautious in explaining the results of the expressed channels in HEK293 cells. A control should be necessary.

Key words: Potassium channels, Whole-cell recording