Elementary events of agonist-induced Ca2+ release in vascular endothelial cells.
The subcellular spatial and temporal organization of agonist-induced Ca2+ signals was investigated in single cultured vascular endothelial cells. Extracellular application of ATP initiated a rapid increase of intracellular Ca2+ concentration ([Ca2+]i) in peripheral cytoplasmic processes from where activation propagated as a [Ca2+]i wave toward the central regions of the cell. The average propagation velocity of the [Ca2+]i wave in the peripheral processes was 20-60 microns/s, whereas in the central region the wave propagated at < 10 microns/s. The time course of the recovery of [Ca2+]i depended on the cell geometry. In the peripheral processes (i.e., regions with a high surface-to-volume ratio) [Ca2+]i declined monotonically, whereas in the central region [Ca2+]i decreased in an oscillatory fashion. Propagating [Ca2+]i waves were preceded by small, highly localized [Ca2+]i transients originating from 1- to 3-micron-wide regions. The average amplitude of these elementary events of Ca2+ release was 23 nM, and the underlying flux of Ca2+ amounted to approximately 1-2 x 10(-18) mol/s or approximately 0.3 pA, consistent with a Ca2+ flux through a single or small number of endoplasmic reticulum Ca(2+)-release channels.
Hüser
J
J
Department of Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153, USA.
Blatter
L A
LA
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002467:Cell Nucleus / Q000187:drug effects / Q000502:physiology; D048429:Cell Size; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D018613:Microscopy, Confocal; D011651:Pulmonary Artery; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D000255:Adenosine Triphosphate; D002118:Calcium