Ca2+ sparks and embers of mammalian muscle. Properties of the sources

Zhou, Jin Song, Brum, Gustavo, Gonzalez, Adom, Launikonis, Bradley S., Stern, Michael D. and Rios, Eduardo (2003) Ca2+ sparks and embers of mammalian muscle. Properties of the sources. Journal of General Physiology, 122 1: 95-114. doi:10.1085/jgp.200308796

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Author Zhou, Jin Song
Brum, Gustavo
Gonzalez, Adom
Launikonis, Bradley S.
Stern, Michael D.
Rios, Eduardo
Title Ca2+ sparks and embers of mammalian muscle. Properties of the sources
Journal name Journal of General Physiology   Check publisher's open access policy
ISSN 0022-1295
Publication date 2003-07
Sub-type Article (original research)
DOI 10.1085/jgp.200308796
Open Access Status File (Publisher version)
Volume 122
Issue 1
Start page 95
End page 114
Total pages 20
Place of publication New York
Publisher Rockefeller University Press
Language eng
Abstract Ca2+ sparks of membrane-pcrmeabilized rat muscle cells were analyzed to derive properties of their sources. Most events identified in longitudinal confocal line scans looked like sparks, but 23% (1,000 out of 4,300) were followed by long-lasting embers. Some were preceded by embers, and 48 were "lone embers." Average spatial width was similar to2 mum in the rat and 1.5 mum in frog events in analogous solutions. Amplitudes were 33% smaller and rise times 50% greater in the rat. Differences were highly significant. The greater spatial width was not a consequence of greater open time of the rat source, and was greatest at the shortest rise times, suggesting a wider Ca2+ source. In the rat, but not the frog, spark width was greater in scans transversal to the fiber axis. These features suggested that rat spark sources were elongated transversally. Ca2+ release was calculated in averages of sparks with long embers. Release current during the averaged ember started at 3 or 7 pA (depending on assumptions), whereas in lone embers it was 0.7 or 1.3 pA, which suggests that embers that trail sparks start with five open channels. Analysis of a spark with leading ember yielded a current ratio ranging from 37 to 160 in spark and ember, as if 37-160 channels opened in the spark. In simulations, 25-60 pA of Ca2+ current exiting a point source was required to reproduce frog sparks. 130 pA, exiting a cylindric source of 3 mum, qualitatively reproduced rat sparks. In conclusion, sparks of rat muscle require a greater current than frog sparks, exiting a source elongated transversally to the fiber axis, constituted by 35-260 channels. Not infrequently, a few of those remain open and produce the trailing ember.
Keyword Physiology
sarcoplasmic reticulum
intracellular channels
excitation-contraction coupling
ryanodine receptors
Frog Skeletal-muscle
Ryanodine Receptor
Elementary Events
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biomedical Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 56 times in Thomson Reuters Web of Science Article | Citations
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Created: Wed, 19 Sep 2007, 17:33:53 EST