Vol. 58, Issue 6, 1368-1374, December 2000

2-Aminoethoxydiphenyl Borate Modulates Kinetics of Intracellular Ca²⁺ Signals Mediated by Inositol 1,4,5-Trisphosphate-Sensitive Ca²⁺ Stores in Single Pancreatic Acinar Cells of Mouse

Jie Wu,¹ Noritaka Kamimura, Teruko Takeo, Sechiko Suga, Makoto Wakui, Takayuki Maruyama, and Katsuhiko Mikoshiba

Department of Physiology, Hirosaki University School of Medicine, Hirosaki, Japan (J.W., N.K., T.T., S.S., M.W.); Minase Research Institute, Ono Pharmacological Company, Osaka, Japan (T.M.); and Department of Molecular Neurobiology, Institute of Medical Science, Tokyo University, Tokyo, Japan (K.M.)

Regulation of the kinetics of intracellular Ca²⁺ signals with a novel, membrane-penetrable, inositol 1,4,5-trisphosphate (InsP₃) receptor/Ca²⁺ channel modulator, 2-amino-ethoxydiphenyl borate (2APB), has been investigated using patch-clamp, whole-cell recording to monitor Ca²⁺-activated Cl currents in single isolated pancreatic acinar cells. 2APB itself fails to evoke a detectable current response but it dramatically changes the kinetics of agonist-induced Ca²⁺ release from pulsatile spikes to long-lasting, huge Ca²⁺ waves, suggesting that 2APB coordinates local Ca²⁺ release to generate global Ca²⁺ signals. The regulation by 2APB can be elicited by internal perfusion of InsP₃ in a concentration-dependent manner, indicating that this regulation is not mediated through membrane receptors or G protein signal transduction. The InsP₃ receptor blocker heparin, but not the ryanodine-sensitive receptor blockers ruthenium red or ryanodine, abolishes 2APB-mediated regulation of Ca²⁺ release. This results also suggest that 2APB effects are mediated through InsP₃ receptors. 2APB substantially modifies single inward Cl current pulse evoked by the photolytic release of caged InsP₃ but not by caged Ca²⁺. These data indicate that 2APB-induced regulation is mediated neither by Ca²⁺-induced Ca²⁺ release nor by affecting Cl channel activity directly. We conclude that 2APB regulates the kinetics of intracellular Ca²⁺ signals, represented as the change in the Ca²⁺ oscillation patterns from brief pulsatile spikes to huge, long-lasting Ca²⁺ waves. Moreover, this regulation seems to be mediated through InsP₃-sensitive Ca²⁺ pools. 2APB may act as a novel, useful pharmacological tool to study the genesis of intracellular Ca²⁺ signals.