Depletion of intracellular Ca2+ stores activates a Ca(2+)-selective channel in vascular endothelium.
The present study was designed to identify the channel responsible for Ca2+ influx after depletion of intracellular Ca2+ stores. Different maneuvers that deplete intracellular Ca2+ stores activated a Ca(2+)-selective channel. Superfusion of single bovine aortic endothelial cells with 50 nmol/l bradykinin, 10 mumol/l ATP, or 10 mumol/l 2,5-di(tert-butyl)-1,4-benzohydroquinone produced activation of channels of the same amplitude in cell-attached patches. Channel activity declined within the first minute after patch excision. The channel showed strong inward rectification and a reversal potential of 0 mV in symmetrical sodium sulfate (Na2SO4) solution. Under these conditions, the conductance was 5 pS in the inward direction. Addition of 10 mmol/l Ca2+ to the extracellular solution shifted the reversal potential to +30 +/- 5 mV, and the conductance for inward current was 11 pS. The reversal potential was used to calculate an ion permeability ratio of Ca2+/Na+ > 10:1.
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Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Kunze
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000172:deficiency* / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D004553:Electric Conductivity; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006873:Hydroquinones / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology
D015220:Calcium Channels; D006873:Hydroquinones; C019359:2,5-di-tert-butylhydroquinone; D007811:Lanthanum; D000255:Adenosine Triphosphate; D001920:Bradykinin; D002118:Calcium