Calcium channels activated by depletion of internal calcium stores in A431 cells.
Depletion of intracellular calcium stores induces transmembrane Ca2+ influx. We studied Ca(2+)- and Ba(2+)-permeable ion channels in A431 cells after store depletion by dialysis of the cytosol with 10 mM BAPTA solution. Cell-attached patches of cells held at low (0.5 microM) external Ca2+ exhibited transient channel activity, lasting for 1-2 min. The channel had a slope conductance of 2 pS with 200 mM CaCl2 and 16 pS with 160 mM BaCl2 in the pipette. Channel activity quickly ran down in excised inside-out patches and was not restored by InsP3 and/or InsP4. Thapsigargin induced activation in cells kept in 1 mM external Ca2+ after BAPTA dialysis. These channels represent one Ca2+ entry pathway activated by depletion of internal calcium stores and are clearly distinct from previously identified calcium repletion currents.
Lückhoff
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Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905.
Clapham
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D017609:Barium Compounds / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002294:Carcinoma, Squamous Cell; D002448:Cell Adhesion; D002460:Cell Line; D002712:Chlorides / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004553:Electric Conductivity; D006801:Humans; D007295:Inositol Phosphates / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D015636:Magnesium Chloride / Q000494:pharmacology; D008564:Membrane Potentials; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014407:Tumor Cells, Cultured
D017609:Barium Compounds; D016227:Benzoquinones; D015220:Calcium Channels; D002712:Chlorides; D007295:Inositol Phosphates; D013729:Terpenes; D015636:Magnesium Chloride; C024986:barium chloride; C067344:2,5-di-tert-butylbenzoquinone; D004533:Egtazic Acid; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002122:Calcium Chloride; D002118:Calcium