Slow depletion of endoplasmic reticulum Ca(2+) stores and block of store-operated Ca(2+) channels by 2-aminoethoxydiphenyl borate in mouse pancreatic acinar cells

• Published in: Naunyn-Schmiedeberg's archives of pharmacology 2002-05, Vol.365 (5), p.399-405
• Main Authors: Park, Myoung Kyu, Lee, Kawang Kook, Uhm, Dae-Yong
• Format: Article
• Language: English
• Subjects: Animals; Boron Compounds - pharmacology; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Calcium Channels - drug effects; Calcium Channels - physiology; Calcium Signaling - physiology; Cells, Cultured; Dose-Response Relationship, Drug; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Inositol 1,4,5-Trisphosphate Receptors; Mice; Pancreas - cytology; Pancreas - drug effects; Pancreas - metabolism; Receptors, Cytoplasmic and Nuclear - antagonists & inhibitors; Time Factors
• ISSN: 0028-1298
• DOI: 10.1007/s00210-002-0535-0

The compound 2-aminoethoxydiphenyl borate (2-APB) has been used as either a specific membrane-permeable inhibitor for InsP(3) receptors or a store-operated Ca(2+) channel blocker in some cells. In this study, we have investigated actions of 2-APB on Ca(2+) signalling in mouse pancreatic acinar cells by measuring Ca(2+) concentration in the cytosol ([Ca(2+)]c) and in the endoplasmic reticulum (ER). Although 2-APB (50 microM) inhibited or modulated [Ca(2+)]c oscillations generated by a low dose of ACh, it did not block InsP(3)-mediated Ca(2+) release from the ER elicited by high doses of acetylcholine (ACh). 2-APB alone more than 70 microM tended to increase [Ca(2+)]c. When we directly measured Ca(2+) concentration in the lumen of the ER with a low affinity Ca(2+) dye, Mag-fluo-4, 2-APB itself slowly lowered ER Ca(2+) concentration and ACh could further release Ca(2+) from the ER in the presence of 2-APB, suggesting its lack of potency to block InsP(3) receptors. When store-operated Ca(2+) entry was evoked by addition of external Ca(2+) (5 mM) after depletion of Ca(2+) stores, 2-APB (50 microM) substantially blocked the Ca(2+) influx in a reversible manner. We conclude that (a) 2-APB is a good blocker for store-operated Ca(2+) channels, (b) 2-APB could not effectively block InsP(3) receptors, and (c) low doses of 2-APB lower Ca(2+) concentration in the lumen of the ER without a significant elevation of [Ca(2+)]c.