Regulation of intracellular calcium oscillations in porcine tracheal smooth muscle cells.
Using real-time confocal microscopy, we examined the dynamic intracellular Ca2+ concentration ([Ca2+]i) response of porcine tracheal smooth muscle (TSM) cells to acetylcholine (ACh). Exposure to ACh caused regenerative, propagating [Ca2+]i oscillations. The amplitude and fall time of the [Ca2+]i oscillations were inversely correlated to basal [Ca2+]i, whereas the frequency and rise time were directly correlated to basal [Ca2+]i. ACh-induced [Ca2+]i oscillations were initiated in the absence of extracellular Ca2+ and after membrane depolarization with KCl, suggesting that 1) [Ca2+]i oscillations primarily arise by release from internal stores such as the sarcoplasmic reticulum (SR), and 2) Ca2+ influx is necessary for maintenance of oscillations. Exposure to both caffeine and ryanodine inhibited ongoing ACh-induced [Ca2+]i oscillations, suggesting a role for caffeine-sensitive ryanodine receptor (RyR) SR Ca2+ channels. Inhibition of SR Ca2+ reuptake by thapsigargin increased basal [Ca2+]i and decreased [Ca2+]i oscillation amplitude, suggesting that Ca2+ reuptake is also essential. The present results suggest that [Ca2+]i oscillations in porcine TSM cells involve repetitive Ca2+ release and reuptake from RyR channels, perhaps through a Ca2+ -induced Ca2+ release mechanism.
Prakash
Y S
YS
Department of Anesthesiology, Mayo Foundation, Rochester, Minnesota 55905, USA.
Kannan
M S
MS
Sieck
G C
GC
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D002451:Cell Compartmentation; D002478:Cells, Cultured; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D008564:Membrane Potentials; D009124:Muscle Proteins / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D010507:Periodicity; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000502:physiology; D013552:Swine; D014132:Trachea / Q000502:physiology*
D015220:Calcium Channels; D009124:Muscle Proteins; D018377:Neurotransmitter Agents; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D015544:Inositol 1,4,5-Trisphosphate; D000109:Acetylcholine; D002118:Calcium