Multiple mechanisms of manganese-induced quenching of fura-2 fluorescence in rat mast cells.
Whole-cell patch-clamp recordings of membrane currents and fura-2 measurements of free intracellular calcium concentration ([Ca2+]i) were used to study Mn2+ influx in rat peritoneal mast cells. The calcium-selective current, activated by depletion of intracellular calcium stores (ICRAC for calcium release-activated calcium current), supports a small but measurable Mn2+ current. In the presence of intracellular BAPTA, a Mn2+ current through ICRAC was recorded in isotonic MnCl2 (100 mM) without a significant quenching of fura-2 fluorescence. Its amplitude was 10% of that measured in physiological solution containing 10 mM Ca2+. However, following store depletion, a significant quenching of fura-2 fluorescence could be measured only when intracellular BAPTA was omitted, so that all the incoming Mn2+ could be captured by the fluorescent dye. Two other ionic currents activated by receptor stimulation also induced Mn2+ quenching of fura-2 fluorescence: a small current through non-specific cation channels of 50-pS unitary conductance and a distinct cationic current of large amplitude. In addition to these influx mechanisms, Mn2+ was taken up into calcium stores and was subsequently co-released with Ca2+ by Ca(2+)-mobilizing agonists.
Fasolato
C
C
Department of Membrane Biophysics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Hoth
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M
Penner
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R
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004553:Electric Conductivity; D005456:Fluorescent Dyes; D016257:Fura-2; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000378:metabolism* / Q000494:pharmacology; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence
D005456:Fluorescent Dyes; D008345:Manganese; D004533:Egtazic Acid; D015544:Inositol 1,4,5-Trisphosphate; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium; D016257:Fura-2