Abstract
The aim of the present study was to investigate the direct effects of a reactive oxygen species, H2O2, on the contractile function and sarcoplasmic reticulum properties of dystrophin-deficient diaphragm using chemically skinned fibers and sarcoplasmic reticulum vesicle preparations. The results obtained using Triton X-100-skinned fibers demonstrate that exposure to 1mMH2O2 had similar effects on the maximal Ca2+-activated tension and on the Ca2+ sensitivity of the contractile apparatus of diaphragm fibers in Bl10 and mdx mice. The effects of H2O2 were also assessed on sarcoplasmic reticulum function using saponin-skinned fibers and sarcoplasmic reticulum vesicle preparations. We found that H2O2 induced changes in sarcoplasmic reticulum properties, particularly in the Ca2+ pump function. The most important finding was that diaphragm muscle from mdx mice displayed increased sensitivity to the oxidant. Furthermore, in isolated superfused diaphragm muscle from mdx mice, the data demonstrate that the amount of superoxide anion produced under fatiguing conditions was increased. Our study shows that the sarcoplasmic reticulum, and the Ca2+ pump in particular, in dystrophin-deficient muscles display increased susceptibility to H2O2 injuries. This suggests that free radicals might, therefore, be involved in the pathophysiological pathway and dysregulation of Ca2+ homeostasis of muscular dystrophy.
Footnotes
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doi:10.1124/jpet.106.103291.
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ABBREVIATIONS: DMD, Duchenne muscular dystrophy; SR, sarcoplasmic reticulum; NO, nitric oxide; ROS, reactive oxygen species.
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↵1 This work was performed as part of the Ph.D. requirement.
- Received February 21, 2006.
- Accepted June 23, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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