Properties of a delayed-rectifier K+ channel in a mouse nonfusing muscle cell line

Undifferentiated BC3H1 cells express a potassium-selective channel which was studied using whole-cell patch clamp techniques. The channel exhibits properties comparable to other delayed-rectifier K+ channels, including activation threshold, moderately slow rate of activation, and slow inactivation. The BC3H1 cell channel is strongly sensitive to the resting potential of the cell, with much larger current magnitudes developing from more hyperpolarized holding potentials. Recovery from inactivation is slow and strongly dependent on membrane potential, becoming more rapid at hyperpolarized voltages. This channel is somewhat sensitive to extracellular TEA, 4-aminopyridine, and alpha-dendrotoxin, but insensitive to barium, cesium, and charybdotoxin. Dendrotoxin slows deactivation significantly. The voltage dependency and kinetic properties of this channel are consistent with a role in recovery of membrane potential following depolarization or possibly in the process of volume regulation.