A role for phospholipase C activity but not ryanodine receptors in the initiation and propagation of intercellular calcium waves.
Mechanical stimulation of a single cell in an airway epithelial culture initiates an increase in intracellular Ca2+ concentration ([Ca2+]i) that propagates from cell to cell as an intercellular Ca2+ wave. These Ca2+ waves appear to require an increase in intracellular inositol 1,4,5-trisphosphate (IP3) concentration ([IP3]i) in the stimulated cell and are propagated between cells by the diffusion of IP3 through gap junctions. To test the hypothesis that the activation of phospholipase C (PLC) contributes to the elevation of [IP3]i and initiation of an intercellular Ca2+ wave, changes in [Ca2+]i induced by mechanical stimulation were measured by digital fluorescence microscopy in the presence of the PLC inhibitor, aminosteroid U73122. Following exposure to U73122 mechanical stimulation elevated [Ca2+]i of the stimulated cell, but did not initiate the propagation of an intercellular Ca2+ wave. By contrast, in the presence of U73343, a similar aminosteroid that does not inactivate PLC, mechanical stimulation increased the [Ca2+]i of the stimulated cell and initiated an intercellular Ca2+ wave. U73122 also blocked the elevation of [Ca2+]i of airway epithelial cells in response to ATP, a P2-receptor agonist that activates PLC to elevate [IP3]i and [Ca2+]i. In addition, the propagation of intercellular Ca2+ waves was not affected by the ryanodine-receptor agonists, caffeine or ryanodine. The hypotheses that: (1) an elevation of [IP3]i is required to initiate intercellular Ca2+ waves; (2) mechanical stimulation activates PLC; and (3) Ca2+ wave propagation in airway epithelial cells involves Ca2+ release from intracellular stores primarily via IP3 receptors are supported by these results.
Hansen
M
M
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
Boitano
S
S
Dirksen
E R
ER
Sanderson
M J
MJ
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D002923:Cilia / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D004963:Estrenes / Q000494:pharmacology; D007700:Kinetics; D009092:Mucous Membrane / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D011817:Rabbits; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014132:Trachea / Q000166:cytology / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D004963:Estrenes; D009124:Muscle Proteins; D011760:Pyrrolidinones; D019837:Ryanodine Receptor Calcium Release Channel; D013729:Terpenes; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D012433:Ryanodine; D002110:Caffeine; D019284:Thapsigargin; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; D002118:Calcium