Detection of ligand-activated conductive Ca2+ channels in human B lymphocytes.
It has been assumed that uptake of extracellular Ca2+ occurs through ligand-activated Ca2+ channels in anti-IgM stimulated human B cells. If so, then uptake should be associated with a depolarizing inward current. Instead, a hyperpolarization due to Ca2+-sensitive K+ conductance is observed. To demonstrate conductive Ca2+ channels in human B lymphocytes, we loaded the cells with 1,2-bis-(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetate (BAPTA), an intracellular Ca2+ chelating agent. This increased the magnitude of the Ca2+ current and delayed the Ca2+-dependent K+ conductance. In BAPTA-loaded B cells suspended in Ca2+-free medium and activated with anti-IgM, reintroduction of Ca2+ resulted in a depolarization that was inhibited by high (microM) concentrations of verapamil and was observed when Ca2+ was replaced by Ba2+ but not Mg2+. These data demonstrate the opening of selective, Ca2+ conductive channels in human B cells following cross-linking of surface immunoglobulins.
MacDougall
S L
SL
Division of Immunology, Hospital for Sick Children, Toronto, Ontario, Canada.
Grinstein
S
S
Gelfand
E W
EW
D001402:B-Lymphocytes / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents; D004533:Egtazic Acid / Q000031:analogs & derivatives; D006801:Humans; D007202:Indicators and Reagents; D007473:Ion Channels / Q000032:analysis*; D008024:Ligands; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism
D002614:Chelating Agents; D007202:Indicators and Reagents; D007473:Ion Channels; D008024:Ligands; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011188:Potassium; D002118:Calcium