Are Ca2+ channels in neutrophils activated by a rise in cytosolic free Ca2+?
It was recently suggested that the opening of neutrophil plasma membrane Ca2+ channels by chemotactic agents is mediated by a rise in free cytosolic Ca2+ concentration ([Ca2+]i). This hypothesis was tested in human cells monitoring [Ca2+]i with the indicator indo-1. In cells loaded with the Ca2+-chelating agent bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetate, transmembrane Ca2+ uptake could be stimulated by formyl-methionyl-leucyl-phenylalanine (fMLP) even when [Ca2+]i was at or below the resting level. In contrast, simply elevating [Ca2+]i in unstimulated cells failed to increase transmembrane uptake. It was concluded either that Ca2+ uptake across the plasma membrane is activated directly by the formation of the chemotactic factor-receptor complex or, more likely, that a transduction mechanism distinct from changes in [Ca2+]i is involved.
D002118:Calcium / Q000097:blood*; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D007202:Indicators and Reagents; D007211:Indoles; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D007211:Indoles; D007473:Ion Channels; D004533:Egtazic Acid; D009240:N-Formylmethionine Leucyl-Phenylalanine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; C048960:indo-1; D002118:Calcium