Received November 8, 2006
Revised November 22, 2006
Accepted after revision November 27, 2006
Human, Environmental & Exercise [250]
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Ultrastructural changes and SR Ca2+ regulation in red vastus muscle following eccentric exercise in the rat
Wan Chen 1,
Patricia A Ruell 1,
Majid Ghoddusi 2,
Anthony Kee 2,
Edna C Hardeman 2,
Kylie M Hoffman 1,
Martin W Thompson 1*
1 The University of Sydney
2 Children's Medical Research Institute
* To whom correspondence should be addressed. E-mail: m.thompson{at}fhs.usyd.edu.au.
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Abstract |
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This study examined the effects of a bout of low-intensity, prolonged downhill exercise on sarcoplasmic reticulum (SR) Ca2+-ATPase activity, Ca2+-uptake and release in rat red vastus muscle. Ionophore stimulation was determined to assess vesicle integrity by measuring the ratio of Ca2+-ATPase activities in the presence and absence of A23187. Observations of the muscle ultrastructure were made to evaluate muscle damage at the level of the myofibrils and SR. Adult male Sprague-Dawley rats (wt = 395 ± 5.9g) were either assigned as non-exercise controls or subjected to 90-min of downhill treadmill exercise (-16°; 15 m.min-1 ), and then sacrificed immediately, 4, 24, 48, 72 and 144h after exercise (n = 7). Ca2+-uptake was significantly lower (p < 0.05) compared with control (19.25 ± 1.38 nmol.min-1.mg protein-1), by 29% and 36% immediately and 4h post-exercise, respectively, and remained depressed (p < 0.05) 24h post-exercise. Ca2+-release was also significantly lower (p < 0.05) compared with control (31.06 ± 2.36), by 37% and 39% immediately and 4h post-exercise, respectively, and remained depressed (p < 0.05) 24h post-exercise. Ca2+-ATPase activity measured with ionophore was 31% lower (p < 0.05) 4h post-exercise, and remained lower (p < 0.05) 24h post-exercise. The ratio of Ca2+-ATPase activities in the presence and absence of A23187 was not significantly changed after exercise, indicating membrane integrity was not altered by the exercise. Focal dilations of the SR were observed immediately and 4h following exercise, implying that SR may be susceptible to damage in the localized regions of overstretched sarcomeres. The results demonstrate that a bout of low-intensity, prolonged downhill exercise results in a long-lasting depression of SR function that is not fully restored after two days of recovery, which may underlie some functional impairments induced by eccentric exercise.
Key Words:
Exercise, Sarcoplasmic reticulum, Skeletal muscle
