For electrochemical measurements cells were grown on an tissue culture dishes (SARSTEDT, TC Dish 35, ref. 83.3900) on which described above pencil electrode has been installed. To properly position the working electrode a small orifice was burned out in the side of the culture dish using a hot metal rod, the electrode was positioned inside and held in place using hot glue. Regular passages were made, where cells were maintained in a logarithmic growth phase. The working electrode was in the cell culture without interruptions during the whole timeframe of the experiment, the reference and counter electrodes were positioned in the cell culture medium from the top for the time of the individual measurements.