Ca(2+)-dependent suppression of inwardly rectified K+ channels in rat basophilic leukemia cells

A patch clamp technique was used in rat basophilic leukemia (RBL) cells to reveal the response properties of K+ Channels at different membrane potentials and the effects of Ca2+ on channel activity. In the whole-cell, cell-attached and inside-out clamp configurations, inward K+ currents markedly increased with increasing hyperpolarization, showing the inwardly rectifying property of the currents. Mean amplitude of inward K+ currents was smaller with larger (1-10 microM) internal Ca2+ than with low (less than or equal to 100 nM) internal Ca2+, indicating that high concentrations of internal Ca2+ suppress channel activity. Single channel currents and the conductance of channels were not changed by high internal Ca2+ concentrations, but the open probability of the channels was decreased in these conditions. The results suggest that, by changing K+ channel activity, Ca2+ is a factor in the regulation of inwardly rectified K+ currents in RBL cells.