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 patchclamp, 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.
ASJC Scopus subject areas
- Molecular Medicine