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Cross-bridge kinetics in fatigued mouse diaphragm.
C Coirault1, P Attal, F X Blanc
1INSERM 451-Laboratoire d'Optique Appliquée-Ecole Polytechnique, Palaiseau, France.
The European Respiratory Journal
|July 22, 1999
Summary
Diaphragm fatigue reduces the number of active cross-bridges, impacting muscle tension. Recovery restores cross-bridge numbers but not detachment rates, suggesting impaired adenosine diphosphate release.
Area of Science:
- Muscle Physiology
- Biophysics
Background:
- Muscle fatigue is a complex phenomenon affecting muscle performance.
- Understanding the behavior of cross-bridges during fatigue is crucial for respiratory muscle research.
Purpose of the Study:
- To quantify cross-bridge dynamics in the diaphragm during fatigue and early recovery.
- To investigate the relationship between cross-bridge kinetics and muscle tension changes.
Main Methods:
- Isolated mouse diaphragm experiments (n=10).
- Calculation of cross-bridge parameters (force, number, cycle time, rate constants) using Huxley's equations.
- Fatigue protocol followed by a 15-minute recovery period.
Main Results:
- Peak isometric tension and shortening velocity decreased significantly post-fatigue.
- The number of active cross-bridges (m) decreased by approximately 40% and recovered within 10 minutes.
- The rate constant for cross-bridge detachment (g2) decreased with fatigue and remained low during recovery.
- Force per cross-bridge (pi) and attachment rate (f1) were unchanged.
Conclusions:
- Diaphragm tension changes during fatigue and recovery correlate with alterations in the number of active cross-bridges, not force per cross-bridge.
- Fatigue may impair adenosine diphosphate release from the actomyosin complex, affecting cross-bridge detachment kinetics.
- These findings offer insights into the mechanisms of respiratory muscle fatigue and recovery.