DEPLETION OF INTRACELLULAR CALCIUM STORES ACTIVATES AN OUTWARD POTASSIUM CURRENT IN MAST AND RBL-1 CELLS THAT IS CORRELATED WITH CRAC CHANNEL ACTIVATION

Highly Ca2+ selective Ca2+ channels activated by store depletion have been recently described in several cell types and have been termed CRA C channels (for calcium release-activated calcium). The present study shows that following store depletion in mast and RBL-1 cells, monovale nt outward currents could be recorded if the internal solution contain ed K+ but not Cs+. The activation of the outward K+ current correlated with the activation of I-CRAC, in both time and amplitude, suggesting that the K+ current might be carried by CRAC channels. The amplitude of the outward current was increased if external Ca2+ was reduced or r eplaced by external Ba2+. The outward K+ conductance might have a phys iological role in maintaining the driving force for Ca2+ entry during the activation of CRAC channels.