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Focal agonist stimulation results in spatially restricted Ca 2+ release and capacitative Ca 2+ entry in bovine vascular endothelial cells
Author(s) -
Hüser Jörg,
Holda Jaclyn R.,
Kockskämper Jens,
Blatter Lothar A.
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.101af.x
Subject(s) - stimulation , intracellular , purinergic receptor , biophysics , endoplasmic reticulum , inositol , agonist , chemistry , receptor , extracellular , inositol trisphosphate , biology , biochemistry , endocrinology
1 Intracellular Ca 2+ ([Ca 2+ ] i ) signals were studied with spatial resolution in bovine vascular endothelial cells using the fluorescent Ca 2+ indicator fluo‐3 and confocal laser scanning microscopy. Single cells were stimulated with the purinergic receptor agonist ATP resulting in an increase of [Ca 2+ ] i due to intracellular Ca 2+ release from inositol 1,4,5‐trisphosphate (IP 3 )‐sensitive stores. ATP‐induced Ca 2+ release was quantal, i.e. submaximal concentrations mobilized only a fraction of the intracellularly stored Ca 2+ . 2 Focal receptor stimulation in Ca 2+ ‐free solution by pressure application of agonist‐containing solution through a fine glass micropipette resulted in a spatially restricted increase in [Ca 2+ ] i . Ca 2+ release was initiated at the site of stimulation and frequently propagated some tens of micrometres into non‐stimulated regions. 3 Local Ca 2+ release caused activation of capacitative Ca 2+ entry (CCE). CCE was initially colocalized with Ca 2+ release. Following repetitive focal stimulation, however, CCE became detectable at remote sites where no Ca 2+ release had been observed. In addition, the rate of Ca 2+ store depletion with repetitive local activation of release in Ca 2+ ‐free solution was markedly slower than that elicited by ATP stimulation of the entire cell. 4 From these experiments it is concluded that both intracellular IP 3 ‐dependent Ca 2+ release and activation of CCE are controlled locally at the subcellular level. Moreover, redistribution of intracellular Ca 2+ stored within the endoplasmic reticulum efficiently counteracts local store depletion and accounts for the spatial spread of CCE activation.