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

Regulation of the kinetics of intracellular Ca2+ signals with a novel, memb rane-penetrable, inositol 1,4,5-trisphosphate (InsP(3)) receptor/Ca2+ chann el modulator, 2-amino-ethoxydiphenyl borate (2APB), has been investigated u sing patch-clamp, whole-cell recording to monitor Ca2+-activated Cl- curren ts in single isolated pancreatic acinar cells. 2APB itself fails to evoke a detectable current response but it dramatically changes the kinetics of ag onist-induced Ca2+ release from pulsatile spikes to long-lasting, huge Ca2 waves, suggesting that 2APB coordinates local Ca2+ release to generate glo bal Ca2+ signals. The regulation by 2APB can be elicited by internal perfus ion of InsP(3) in a concentration-dependent manner, indicating that this re gulation is not mediated through membrane receptors or G protein signal tra nsduction. The InsP(3) receptor blocker heparin, but not the ryanodine-sens itive receptor blockers ruthenium red or ryanodine, abolishes 2APB-mediated regulation of Ca2+ release. This results also suggest that 2APB effects ar e mediated through InsP(3) receptors. 2APB substantially modifies single in ward Cl- current pulse evoked by the photolytic release of caged InsP(3) bu t not by caged Ca2+. These data indicate that 2APB-induced regulation is me diated neither by Ca2+-induced Ca2+ release nor by affecting Cl- channel ac tivity directly. We conclude that 2APB regulates the kinetics of intracellu lar Ca2+ signals, represented as the change in the Ca2+ oscillation pattern s from brief pulsatile spikes to huge, long-lasting Ca2+ waves. Moreover, t his regulation seems to be mediated through InsP(3)-sensitive Ca2+ pools. 2 APB may act as a novel, useful pharmacological tool to study the genesis of intracellular Ca2+ signals.