Regulation of intracellular calcium oscillations in porcine
tracheal smooth muscle cells.
Prakash, Y. S., Mathur S. Kannan, and Gary C. Sieck.
Departments of Anesthesiology, and Physiology & Biophysics,
Mayo Foundation, Rochester, MN 55905, Department of Veterinary
PathoBiology, University of Minnesota, St. Paul, MN 55108
APStracts 3:0313C, 1996.
Using real-time confocal microscopy, we examined the dynamic [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, while 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 following 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 a 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.
Received 13 June 1996; accepted in final form 9 September 1996.
APS Manuscript Number C337-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996