Fig. 3. Kir2.1 current is inhibited by a tyrosine phosphatase inhibitor. Kir2.1 currents were recorded by whole-cell patch-clamp technique in myoblasts induced to differentiate for 24 hours with a patch pipette containing or not (control) 100 µM bpV(Phen). (A) Kir2.1 currents recorded from myoblasts cultured for 24 hours in DM, in the absence (top) or in the presence (middle) of 100 µM bpV(Phen), or in the presence of both 100 µM bpV(Phen) and 100 µM genistein (bottom). Left traces represent currents recorded after 1 minute and right traces after 25 minutes. Voltage-steps were to -40, -60, -80, -100, -120 and -140 mV from a holding potential at -60 mV. (B) Mean Kir2.1 current amplitude assessed every 10 seconds during a 300 ms step to -120 mV from a holding potential at -60 mV in the absence (n=3) or in the presence (n=5) of 100 µM bpV(Phen), or in the presence of both 100 µM bpV(Phen) and 100 µM genistein (n=3) in the pipette solution. Currents are normalized to the initial current measured 1 minute after breaking the patch. Even though 10 µM genistein was added to the culture medium 2 hours before performing the recordings with both bpV(Phen) and genistein in the pipette, a complete maintenance of channel activity was not achieved.