Calcium entry activated by store depletion in human umbilical vein endothelial cells.
We have used the patch clamp technique combined with simultaneous measurement of intracellular Ca2+ to record ionic currents activated by depletion of intracellular Ca(2+)-stores in endothelial cells from human umbilical veins. Two protocols were used to release Ca2+ from intracellular stores, i.e. loading of the cells via the patch pipette with Ins(1,4,5)P3, and extracellular application of thapsigargin. Ins(1,4,5)P3 (10 microM) evoked a transient increase in [Ca2+]i in cells exposed to Ca(2+)-free extracellular solutions. A subsequent reapplication of extracellular Ca2+ induced an elevation of [Ca2+]i. These changes in [Ca2+]i were very reproducible. The concomitant membrane currents were neither correlated in time nor in size with the changes in [Ca2+]i. Similar changes in [Ca2+]i and membrane currents were observed if the Ca(2+)-stores were depleted with thapsigargin. Activation of these currents was prevented and holding currents at -40 mV were small if store depletion was induced in the presence of 50 microM NPPB. This identifies the large currents, which are activated as a consequence of store-depletion, as mechanically activated Cl- currents, which have been described previously [1,2]. Loading the cells with Ins(1,4,5)P3 together with 10 mM BAPTA induced only a very short lasting Ca2+ transient, which was not accompanied by activation of a detectable current, even in a 10 mM Ca(2+)-containing extracellular solution. Also thapsigargin does not activate any membrane current if the pipette solution contains 10 mM BAPTA (ruptured patches). The contribution of Ca(2+)-influx to the membrane current during reapplication of 10 mM extracellular calcium to thapsigargin-pretreated cells was estimated from the first time derivative of the corresponding Ca2+ transients at different holding potentials. These current values showed strong inward rectification, with a maximal amplitude of 1.0 +/- 0.3 pA at -80 mV (n = 8; membrane capacitance 59 +/- 9 pF).(ABSTRACT TRUNCATED AT 250 WORDS)
KU Leuven, Laboratorium voor Fysiologie, Belgium.
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Oike
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Gericke
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Droogmans
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Nilius
D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials; D009579:Nitrobenzoates / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014471:Umbilical Veins
D018118:Chloride Channels; D009579:Nitrobenzoates; D013729:Terpenes; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D004533:Egtazic Acid; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium