Calcium and barium permeation through calcium release-activated calcium (CRAC) channels

✍ Scribed by Markus Hoth

• Book ID: 104746927
• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 885 KB
• Volume: 430
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00373905

✦ Synopsis

A Ca 2+ current activated by store depletion has been described recently in several cell types and has been termed/CRAC (for Ca 2+ release-activated Ca 2+ current). In this paper, the Ca 2+ and Ba 2+ permeability of CRAC channels is investigated in mast cells, rat basophilic leukaemia cells (RBL) and human T-lymphocytes (Jurkat). The selectivity of CRAC channels for Ca 2+ over monovalent cations is identical in all three cell types and is at least as high as that of voltage-operated Ca 2+ (VOC) channels in the various tissues tested. The amplitude of Ba 2+ currents relative to Ca 2+ currents (IBa/Ica) through CRAC channels was found to be strongly dependent on the membrane potential and was much smaller in Jurkat cells compared to mast and RBL cells. An anomalous mole-fraction behavior was observed at very negative membrane potentials in all three cell types when using different mixtures of external Ca 2+ and Ba 2+. In contrast to VOC channels, the anomalous mole-fraction effect was not observed at potentials positive to -20 mV.