2-Aminoethoxydiphenyl borate modulates kinetics of intracellular Ca(2+) signals mediated by inositol 1,4,5-trisphosphate-sensitive Ca(2+) stores in single pancreatic acinar cells of mouse.
Regulation of the kinetics of intracellular Ca(2+) signals with a novel, membrane-penetrable, inositol 1,4,5-trisphosphate (InsP(3)) receptor/Ca(2+) channel modulator, 2-amino-ethoxydiphenyl borate (2APB), has been investigated using patch-clamp, whole-cell recording to monitor Ca(2+)-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 Ca(2+) release from pulsatile spikes to long-lasting, huge Ca(2+) waves, suggesting that 2APB coordinates local Ca(2+) release to generate global Ca(2+) signals. The regulation by 2APB can be elicited by internal perfusion of InsP(3) in a concentration-dependent manner, indicating that this regulation is not mediated through membrane receptors or G protein signal transduction. The InsP(3) receptor blocker heparin, but not the ryanodine-sensitive receptor blockers ruthenium red or ryanodine, abolishes 2APB-mediated regulation of Ca(2+) release. This results also suggest that 2APB effects are mediated through InsP(3) receptors. 2APB substantially modifies single inward Cl(-) current pulse evoked by the photolytic release of caged InsP(3) but not by caged Ca(2+). These data indicate that 2APB-induced regulation is mediated neither by Ca(2+)-induced Ca(2+) release nor by affecting Cl(-) channel activity directly. We conclude that 2APB regulates the kinetics of intracellular Ca(2+) signals, represented as the change in the Ca(2+) oscillation patterns from brief pulsatile spikes to huge, long-lasting Ca(2+) waves. Moreover, this regulation seems to be mediated through InsP(3)-sensitive Ca(2+) pools. 2APB may act as a novel, useful pharmacological tool to study the genesis of intracellular Ca(2+) signals.
Wu
J
J
Department of Physiology, Hirosaki University School of Medicine, Hirosaki, Japan. jwu2@chw.edu
Kamimura
N
N
Takeo
T
T
Suga
S
S
Wakui
M
M
Maruyama
T
T
Mikoshiba
K
K
D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D010179:Pancreas / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques
D001896:Boron Compounds; D015544:Inositol 1,4,5-Trisphosphate; C109986:2-aminoethoxydiphenyl borate; D002118:Calcium