Spatial and temporal aspects of calcium sparks in porcine tracheal smooth muscle cells.
Spontaneous, localized intracellular Ca(2+) concentration ([Ca(2+)](i)) transients (Ca(2+) sparks) in skeletal, cardiac, and smooth muscle cells are thought to represent Ca(2+) release through ryanodine-receptor (RyR) channels. In porcine tracheal smooth muscle (TSM) cells, ACh induces propagating [Ca(2+)](i) oscillations that also represent Ca(2+) release through RyR channels. We used real-time confocal imaging to examine the spatial and temporal relationships of Ca(2+) sparks to propagating [Ca(2+)](i) oscillations in TSM cells. Ca(2+) sparks within an intracellular region displayed different spatial Ca(2+) distributions with every occurrence. The amplitudes of Ca(2+) sparks within a region were approximately integer multiples of the smallest response. However, across different regions, the attributes of Ca(2+) sparks varied considerably. Individual sparks were often grouped together and coupled across adjacent regions. Fusion of individual sparks produced large local elevations in [Ca(2+)](i) that occasionally triggered a propagating [Ca(2+)](i) wave. The incidence of sparks was increased by ryanodine and caffeine but was unaffected by removal of extracellular Ca(2+). Exposure to ACh triggered repetitive, propagating [Ca(2+)](i) oscillations that always originated from foci with a high spark incidence. The [Ca(2+)](i) oscillations disappeared with the removal of ACh, and Ca(2+) sparks reappeared. We conclude that agonist-induced [Ca(2+)](i) oscillations represent a spatial and temporal integration of local Ca(2+)-release events through RyR channels in TSM cells.
Pabelick
C M
CM
Department of Anesthesiology, Mayo Foundation, Rochester 55905, Minnesota, USA.
Prakash
Y S
YS
Kannan
M S
MS
Sieck
G C
GC
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D007091:Image Processing, Computer-Assisted; D009130:Muscle, Smooth / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D010507:Periodicity; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D013552:Swine; D014132:Trachea / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D014665:Vasodilator Agents / Q000494:pharmacology
D010726:Phosphodiesterase Inhibitors; D019837:Ryanodine Receptor Calcium Release Channel; D014665:Vasodilator Agents; D012433:Ryanodine; D002110:Caffeine; D000109:Acetylcholine; D002118:Calcium