A volume-sensitive, IP3-insensitive Ca2+ store in vascular endothelial cells.
The mechanism by which cell swelling and other physical forces increase the intracellular Ca2+ concentration ([Ca2+]i) is poorly defined. In vascular endothelial cells, the increase in [Ca2+]i after hypotonic swelling was independent of external Ca2+ and membrane potential, was not blocked by La3+ or Gd3+, and was prevented by thapsigargin, indicative of intracellular release. This release also occurred after depletion of agonist-sensitive Ca2+ stores. In cells in which the plasma membrane was permeabilized with saponin, hypotonic medium stimulated release of 45Ca2+ from a thapsigargin-sensitive site. Isosmotic substitutions with sucrose or urea revealed that this release was due specifically to swelling and not to changes in osmolarity or ion concentrations. This volume-sensitive release was inhibited by high concentrations of La3+ and Gd3+ in a time-dependent manner, suggesting inhibition from within the storage compartment. Release was not inhibited by ruthenium red or by prior stimulation with inositol 1,4,5-trisphosphate (IP3), indicating that the volume-sensitive storage site is distinct from mitochondria and from stores sensitive to ryanodine or IP3. The results suggest the presence of a novel, stretch-activated Ca2+ store in endothelial cells that could contribute to their mechanosensitivity.
Jena
M
M
Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Minore
J F
JF
O'Neill
W C
WC
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D003470:Culture Media; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D005682:Gadolinium / Q000494:pharmacology; D007038:Hypotonic Solutions; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D012430:Ruthenium Red / Q000494:pharmacology
D003470:Culture Media; D005456:Fluorescent Dyes; D007038:Hypotonic Solutions; C049925:fura-2-am; D012430:Ruthenium Red; D004533:Egtazic Acid; D007811:Lanthanum; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D005682:Gadolinium; D002118:Calcium; D016257:Fura-2