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Release of calcium into the myofibrillar space in response to active shortening of striated muscle

Edman, K. A.P. LU and Caputo, C (2017) In Acta Physiologica 221(2). p.142-148
Abstract

Aim: The study was undertaken to explore whether shortening of striated muscle during activity is associated with release of bound Ca2+ into the myofibrillar space as has previously been proposed in order to explain the depressant effect of active shortening. Methods: The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres were loaded with the calcium sensitive indicator Fluo-3. The fibres, stimulated to produce a partially fused isometric tetanus, were subjected to a shortening ramp or, alternatively, to a stretch ramp during activity while force, fibre length, sarcomere length and the Fluo-3 signal were recorded. Results: A shortening ramp performed... (More)

Aim: The study was undertaken to explore whether shortening of striated muscle during activity is associated with release of bound Ca2+ into the myofibrillar space as has previously been proposed in order to explain the depressant effect of active shortening. Methods: The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres were loaded with the calcium sensitive indicator Fluo-3. The fibres, stimulated to produce a partially fused isometric tetanus, were subjected to a shortening ramp or, alternatively, to a stretch ramp during activity while force, fibre length, sarcomere length and the Fluo-3 signal were recorded. Results: A shortening ramp performed during a partially fused tetanus caused an increase in the myofibrillar free calcium concentration and produced, simultaneously, a decrease in active force. The isometric force recovered gradually after the shortening ramp, while the intracellular Ca2+ concentration stayed above the control level during the remainder of the stimulation period. A stretch ramp applied during a partially fused tetanus caused a considerably smaller change in the myofibrillar Ca2+ concentration. Conclusion: The results provide evidence that the myosin cross-bridges interact with the calcium binding sites on the thin filaments during active shortening, causing sustained release of calcium and reduced contractile strength.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Muscle fibre, Myofibrillar calcium release, Striated muscle
in
Acta Physiologica
volume
221
issue
2
pages
142 - 148
publisher
Wiley-Blackwell
external identifiers
  • scopus:85017572661
ISSN
1748-1708
DOI
10.1111/apha.12876
language
English
LU publication?
yes
id
a63c2f6b-1988-4400-8724-9ca9d274da7a
date added to LUP
2017-05-08 15:59:45
date last changed
2017-09-20 13:44:08
@article{a63c2f6b-1988-4400-8724-9ca9d274da7a,
  abstract     = {<p>Aim: The study was undertaken to explore whether shortening of striated muscle during activity is associated with release of bound Ca<sup>2+</sup> into the myofibrillar space as has previously been proposed in order to explain the depressant effect of active shortening. Methods: The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres were loaded with the calcium sensitive indicator Fluo-3. The fibres, stimulated to produce a partially fused isometric tetanus, were subjected to a shortening ramp or, alternatively, to a stretch ramp during activity while force, fibre length, sarcomere length and the Fluo-3 signal were recorded. Results: A shortening ramp performed during a partially fused tetanus caused an increase in the myofibrillar free calcium concentration and produced, simultaneously, a decrease in active force. The isometric force recovered gradually after the shortening ramp, while the intracellular Ca<sup>2+</sup> concentration stayed above the control level during the remainder of the stimulation period. A stretch ramp applied during a partially fused tetanus caused a considerably smaller change in the myofibrillar Ca<sup>2+</sup> concentration. Conclusion: The results provide evidence that the myosin cross-bridges interact with the calcium binding sites on the thin filaments during active shortening, causing sustained release of calcium and reduced contractile strength.</p>},
  author       = {Edman, K. A.P. and Caputo, C},
  issn         = {1748-1708},
  keyword      = {Muscle fibre,Myofibrillar calcium release,Striated muscle},
  language     = {eng},
  month        = {04},
  number       = {2},
  pages        = {142--148},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica},
  title        = {Release of calcium into the myofibrillar space in response to active shortening of striated muscle},
  url          = {http://dx.doi.org/10.1111/apha.12876},
  volume       = {221},
  year         = {2017},
}