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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, A., 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. 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 |
|---|---|
| Subjects: | Q Science > QH Natural history > QH301 Biology |
| Divisions: | Faculty of Medicine > Warwick Medical School > Clinical Sciences Research Institute (CSRI) |
| Journal or Publication Title: | Cell Calcium |
| Publisher: | Churchill Livingstone |
| ISSN: | 0143-4160 |
| Date: | September 2007 |
| Volume: | Vol.42 |
| Number: | No.3 |
| Number of Pages: | 9 |
| Page Range: | pp. 303-311 |
| Identification Number: | 10.1016/j.ceca.2006.12.005 |
| Status: | Peer Reviewed |
| Publication Status: | Published |
| Access rights to Published version: | Restricted or Subscription Access |
| URI: | http://wrap.warwick.ac.uk/id/eprint/31572 |
Data sourced from Thomson Reuters' Web of Knowledge
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