Intracellular calcium and force in single mouse muscle fibres following repeated contractions with stretch.

Intracellular calcium and force in single mouse muscle fibres following repeated contractions... 1. The role of the myoplasmic free Ca2+ concentration ((Ca2+)i) in the reduction of muscle force following contractions with stretch was investigated in single fibres from mouse toe muscle. Muscle fibres were either stretched by 25% of their optimum length (Lo) for ten tetani (Protocol I) or stretched by 50% of Lo for between ten and thirty tetani (Protocol II). Indo‐1 was used to measure (Ca2+)i. 2. In each protocol the stretch series was compared with isometric controls; the stretch series always resulted in greater changes in muscle properties than in the isometric controls. The observed changes were (i) reduced tetanic force, (ii) reduced tetanic (Ca2+)i, (iii) increased resting (Ca2+)i and (iv) the greater relative reduction in force at low stimulus frequencies (30 and 50 Hz) compared with high (100 Hz). These changes were maintained for up to 60 min. 3. Stretching a resting muscle fibre had no effect on the subsequent (Ca2+)i or force. 4. Following Protocol I 10 mM caffeine restored tetanic force to pre‐stretch levels. Tetanic (Ca2+)i vs. force curves were constructed pre‐ and post‐stretch and showed that neither the maximum Ca(2+)‐activated force nor the Ca2+ sensitivity of the muscle fibres post‐stretch was significantly different from control. The force reduction, therefore, appears to be the result of reduced tetanic (Ca2+)i. 5. The more severe stretching regimen of Protocol II resulted in a much greater reduction in force than Protocol I. Ten millimolar caffeine did not restore control force. Comparison of the (Ca2+)i‐force relationships pre‐ and post‐stretch showed that the reduction in tetanic force was caused by a combination of a reduced tetanic (Ca2+)i, reduced maximum Ca(2+)‐activated force and reduced Ca2+ sensitivity. 6. Following both protocols the resting (Ca2+)i showed a small rise which persisted for at least 60 min. This elevated (Ca2+)i was associated with a reduction in the pump rate of the sarcoplasmic reticulum Ca2+ pump. 7. This study establishes that reduced Ca2+ release and reduced Ca2+ sensitivity contribute to the reduction in force generating capacity of single mammalian muscle fibres following active stretches. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Physiology Wiley

Intracellular calcium and force in single mouse muscle fibres following repeated contractions with stretch.

The Journal of Physiology, Volume 488 (1) – Oct 1, 1995

Loading next page...
 
/lp/wiley/intracellular-calcium-and-force-in-single-mouse-muscle-fibres-hicyFbtmx4
Publisher
Wiley
Copyright
© 2014 The Physiological Society
ISSN
0022-3751
eISSN
1469-7793
DOI
10.1113/jphysiol.1995.sp020943
Publisher site
See Article on Publisher Site

Abstract

1. The role of the myoplasmic free Ca2+ concentration ((Ca2+)i) in the reduction of muscle force following contractions with stretch was investigated in single fibres from mouse toe muscle. Muscle fibres were either stretched by 25% of their optimum length (Lo) for ten tetani (Protocol I) or stretched by 50% of Lo for between ten and thirty tetani (Protocol II). Indo‐1 was used to measure (Ca2+)i. 2. In each protocol the stretch series was compared with isometric controls; the stretch series always resulted in greater changes in muscle properties than in the isometric controls. The observed changes were (i) reduced tetanic force, (ii) reduced tetanic (Ca2+)i, (iii) increased resting (Ca2+)i and (iv) the greater relative reduction in force at low stimulus frequencies (30 and 50 Hz) compared with high (100 Hz). These changes were maintained for up to 60 min. 3. Stretching a resting muscle fibre had no effect on the subsequent (Ca2+)i or force. 4. Following Protocol I 10 mM caffeine restored tetanic force to pre‐stretch levels. Tetanic (Ca2+)i vs. force curves were constructed pre‐ and post‐stretch and showed that neither the maximum Ca(2+)‐activated force nor the Ca2+ sensitivity of the muscle fibres post‐stretch was significantly different from control. The force reduction, therefore, appears to be the result of reduced tetanic (Ca2+)i. 5. The more severe stretching regimen of Protocol II resulted in a much greater reduction in force than Protocol I. Ten millimolar caffeine did not restore control force. Comparison of the (Ca2+)i‐force relationships pre‐ and post‐stretch showed that the reduction in tetanic force was caused by a combination of a reduced tetanic (Ca2+)i, reduced maximum Ca(2+)‐activated force and reduced Ca2+ sensitivity. 6. Following both protocols the resting (Ca2+)i showed a small rise which persisted for at least 60 min. This elevated (Ca2+)i was associated with a reduction in the pump rate of the sarcoplasmic reticulum Ca2+ pump. 7. This study establishes that reduced Ca2+ release and reduced Ca2+ sensitivity contribute to the reduction in force generating capacity of single mammalian muscle fibres following active stretches.

Journal

The Journal of PhysiologyWiley

Published: Oct 1, 1995

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month