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Myo-mechanical Analysis of Isolated Skeletal Muscle
Published on: February 22, 2011
Myotube phospholipid synthesis and sarcolemmal ATPase activity in dystrophic (mdx) mouse muscle
1Department of Anatomy, University of Manitoba, Winnipeg, Canada.
Abstract:
Phospholipid incorporation of 32P by primary myotube cultures and the tissue activity of sarcolemmal Na+/K(+)-transporting ATPase were studied to determine whether the absence of dystrophin from dystrophic (mdx) muscle would affect membrane lipid synthesis and membrane function. The incorporation of 32P by phospholipid as a ratio with total protein was greater in cultured dystrophic cells compared with control cells. The mdx cells also incorporated more 32P than control cells into phosphatidylethanolamine, which is thought to increase prior to myoblast fusion, and less into phosphatidylserine, phosphatidylinositol, and lysophosphatidylcholine. There was no difference in total protein content or [3H]leucine or 32P incorporation into the aqueous fraction of dystrophic and control cells, although dystrophic cells incorporated less [35S]methionine into protein than controls. Isolated sarcolemma from mdx skeletal muscle tissue demonstrated a consistently greater specific activity of ouabain-sensitive Na+/K(+)-transporting ATPase than sarcolemmal preparations from control skeletal muscle. These observations suggest that cytoskeletal changes such as dystrophin deficiency may alter the differentiation of membrane composition and function.
Insights
Duchenne muscular dystrophy (DMD) in mdx mice alters muscle cell membrane lipid synthesis and function. Dystrophin deficiency affects phospholipid incorporation and increases Na+/K+-transporting ATPase activity in muscle membranes.
Area of Science:
- Biochemistry
- Cell Biology
- Muscle Physiology
Background:
- Duchenne muscular dystrophy (DMD) is characterized by the absence of dystrophin.
- The role of dystrophin in maintaining sarcolemmal integrity and function is crucial.
- Understanding membrane alterations in dystrophin-deficient muscle is key to developing therapies.
Purpose of the Study:
- To investigate the impact of dystrophin absence on membrane lipid synthesis in primary myotubes.
- To assess the activity of sarcolemmal Na+/K+-transporting ATPase in dystrophin-deficient muscle.
- To determine if cytoskeletal changes affect membrane composition and function in mdx muscle.
Main Methods:
- Primary myotube cultures from mdx and control mice were used.
- Phospholipid incorporation of 32P was measured and compared to total protein.
- Specific activity of sarcolemmal Na+/K+-transporting ATPase was analyzed in tissue samples.
Main Results:
- Dystrophic (mdx) myotubes showed increased 32P phospholipid incorporation compared to controls.
- Specific alterations in phosphatidylethanolamine and phosphatidylserine incorporation were observed.
- Sarcolemma from mdx muscle exhibited higher ouabain-sensitive Na+/K+-transporting ATPase activity.
Conclusions:
- Dystrophin deficiency in mdx muscle leads to altered membrane lipid synthesis.
- Increased Na+/K+-transporting ATPase activity suggests functional membrane changes.
- These findings indicate that cytoskeletal alterations impact muscle membrane differentiation and function.
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