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Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
Published on: August 1, 2016
Altered sarcoplasmic reticulum function in rat diaphragm after high-intensity exercise
S Matsunaga1, S Inashima, H Tsuchimochi
1Institute of Health Sciences and Physical Education, Osaka City University, Osaka-shi, Osaka, Japan.
Acta Physiologica Scandinavica
|October 24, 2002
Summary
Acute high-intensity exercise impairs sarcoplasmic reticulum (SR) function in the diaphragm. This reduced SR Ca(2+) handling and Ca(2+)-ATPase activity may decrease exercise tolerance.
Area of Science:
- Exercise Physiology
- Skeletal Muscle Biology
- Cellular Physiology
Background:
- Sarcoplasmic reticulum (SR) plays a crucial role in skeletal muscle excitation-contraction coupling by regulating intracellular calcium (Ca2+).
- Previous studies have indicated that high-intensity exercise affects SR function in locomotor muscles.
Purpose of the Study:
- To investigate the impact of acute high-intensity exercise on Ca2+ handling and Ca2+-adenosine triphosphatase (ATPase) activity of the SR in the rat costal diaphragm.
- To determine if diaphragm SR function is similarly affected by exhaustive exercise as observed in limb muscles.
Main Methods:
- Rats underwent treadmill exercise at 100% maximal O2 consumption until fatigue.
- Sarcoplasmic reticulum (SR) Ca2+ uptake and release rates were measured using the Ca2+ fluorescent dye indo-1.
- SR Ca2+-ATPase activity was assessed in muscle homogenates.
Main Results:
- Exercise significantly increased muscle lactate and inorganic phosphate levels.
- SR Ca2+ uptake and release rates were significantly reduced by 24% and 22%, respectively.
- SR Ca2+-ATPase activity decreased, correlating with the reduced Ca2+ uptake.
Conclusions:
- Acute high-intensity exercise attenuates SR function in the diaphragm, similar to findings in locomotor muscles.
- Impaired SR function in the diaphragm may contribute to reduced exercise tolerance and performance during strenuous physical activity.
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