Calcium and barium permeation through calcium release-activated calcium (CRAC) channels.
A Ca2+ current activated by store depletion has been described recently in several cell types and has been termed ICRAC (for Ca2+ release-activated Ca2+ current). In this paper, the Ca2+ and Ba2+ 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 Ca2+ over monovalent cations is identical in all three cell types and is at least as high as that of voltage-operated Ca2+ (VOC) channels in the various tissues tested. The amplitude of Ba2+ currents relative to Ca2+ 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 Ca2+ and Ba2+. In contrast to VOC channels, the anomalous mole-fraction effect was not observed at potentials positive to -20 mV.
D000818:Animals; D001464:Barium / Q000378:metabolism*; D001711:Biotransformation / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D004594:Electrophysiology; D006801:Humans; D007552:Isotonic Solutions; D015471:Leukemia, Basophilic, Acute / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D013050:Spectrometry, Fluorescence; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D007552:Isotonic Solutions; D001464:Barium; D002118:Calcium