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Evidence that a Ca2+ sparks/STOCs coupling mechanism is responsible for the inhibitory effect of caffeine on electro-mechanical coupling in guinea pig ureteric smooth muscle
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Borisova, L., Shmygol, Anatoly, Wray, Susan and Burdyga, T. (2007) Evidence that a Ca2+ sparks/STOCs coupling mechanism is responsible for the inhibitory effect of caffeine on electro-mechanical coupling in guinea pig ureteric smooth muscle. Cell Calcium, Vol.42 (No.3). pp. 303-311. doi:10.1016/j.ceca.2006.12.005 ISSN 0143-4160.
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Official URL: http://dx.doi.org/10.1016/j.ceca.2006.12.005
Abstract
Recent studies have highlighted the role of the sarcoplasmic reticulurn (SR) in controlling excitability, Ca2+, signalling and contractility in smooth muscle. Caffeine, an agonist of ryanodine receptors (RyRs) on the SR has been previously shown to effect Ca2+, signalling but its effects on excitability and contractility are not so clear. We have studied the effects of low concentration of caffeine (I mM) on Ca2+ signalling, action potential and contractility of guinea pig ureteric smooth muscle. Caffeine produced reversible inhibition of the action potentials, Ca2+, transients and phasic contractions evoked by electrical stimulation. It had no effect on the inward Ca2+ current or Ca 21 transient but increased the amplitude and the frequency of spontaneous transient outward currents (STOCs) in voltage clamped ureteric myocytes, suggesting Ca2+ activated K+ channels (BK) are affected by it. In isolated cells and cells in situ caffeine produced an increase in the frequency and the amplitude of Ca2+ sparks as well the number of spark discharging sites per cell. Inhibition of Ca 2, sparks by ryanodine (50 mu M) or SR Ca2+ ATPase (SERCA) cyclopiazonic acid (CPA, 20 mu M) or BKCa channels by iberiotoxin (200 nM) or TEA (I mM), fully reversed the inhibitory effect of caffeine on Ca2+ transients and force evoked by electrical field stimulation (EFS). These data suggest that the inhibitory effect of caffeine on the action potential, Ca2+ transients and force in ureteric smooth muscle is caused by activation of Ca 2, sparks/STOCs coupling mechanism. (c) 2007 Elsevier Ltd. All rights reserved.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QH Natural history > QH301 Biology | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Medicine > Warwick Medical School | ||||
Journal or Publication Title: | Cell Calcium | ||||
Publisher: | Churchill Livingstone | ||||
ISSN: | 0143-4160 | ||||
Official Date: | September 2007 | ||||
Dates: |
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Volume: | Vol.42 | ||||
Number: | No.3 | ||||
Number of Pages: | 9 | ||||
Page Range: | pp. 303-311 | ||||
DOI: | 10.1016/j.ceca.2006.12.005 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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