2-Aminoethoxydiphenyl Borane Activates a Novel Calcium- Permeable Cation Channel

The membrane-permeable, noncompetitive inositol 1,4,5-trisphosphate (IP3)-receptor inhibitor 2-aminoethoxydiphenyl borane (2-APB) has been widely used to probe for IP3-receptor involvement in calcium signaling pathways. However, a number of recent studies in different cell types revealed other sites of action of 2-APB. In this study, we examined the influence of 2-APB on capacitative calcium entry and intracellular Ca2 concentrations in rat basophilic leukemia (RBL-2H3 m1) cells. 2-APB was found to inhibit capacitative calcium entry, but at concentrations greater than 50 M, a new effect of 2-APB was observed. When capacitative calcium entry was blocked with Gd3, 2-APB caused an increase in cytoplasmic Ca2. This increase in intracellular Ca2 was not caused by altered buff-ering of cytoplasmic Ca2 and was not caused by or in any wa