calcimycin and Muscular-Dystrophy--Animal

Mutations in the dystrophin gene that lead to the expression of truncated forms of the dystrophin protein cause muscular dystrophies of varying severities both in humans and in mice. We have shown previously that dystrophin-deficient muscle is more susceptible to oxidative injury than is normal muscle. In this report, we have used muscle cells derived from mdx mice, which express no dystrophin, and mdx-transgenic strains that express full-length dystrophin or truncated forms of dystrophin to explore further the relationship between dystrophin expression and susceptibility of muscle to oxidative injury. We show that, when differentiated into myotubes, the relative susceptibility of the cell populations to oxidative stress correlates with the severity of the dystrophy in the strain from which the cells were isolated. The most susceptible populations exhibited the greatest oxidative damage as assessed by protein oxidation. Thus, the relative efficacy of truncated dystrophin proteins to protect muscle from necrotic degeneration in vivo is predicted by their ability to protect muscle cells from free radical mediated injury. These findings support the hypothesis that the dystrophin protein complex may have important regulatory or signaling properties in terms of cell survival and antioxidant defense mechanisms.

Topics: Animals; Calcimycin; Cells, Cultured; Dystrophin; Mice; Mice, Inbred mdx; Mice, Transgenic; Muscle, Skeletal; Muscular Dystrophy, Animal; Mutation; Oxidative Stress; Paraquat; Staurosporine; Vitamin K

Topics: Animals; Calcimycin; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Muscles; Muscular Dystrophy, Animal; Prostaglandins E; Reference Values; Regeneration

1. The release of glutathione has been studied in comparison with the release of creatine kinase from isolated rat soleus muscles subjected to certain forms of experimental damage. 2. Excessive electrically stimulated contractile activity or treatment of muscles with the mitochondrial inhibitor, 2,4-dinitrophenol, induced a substantial release of both creatine kinase and glutathione and a reduction in the total glutathione content of the muscle. The time course of this release and depletion indicates that the efflux of the two molecules is not directly related and that a reduction in muscle glutathione content does not occur before cytosolic enzyme release. 3. 2,4-Dinitrophenol-stimulated release of creatine kinase was significantly reduced by the omission of external calcium from the incubation media, but glutathione release and depletion was relatively unaffected by this. Deliberate elevation of the muscle intracellular calcium content with the calcium ionophore, A23187, induced a substantial loss of creatine kinase, but had no significant effect on the release of glutathione. 4. Muscle biopsies from patients with Duchenne muscular dystrophy were found to have an elevated content of glutathione and an equivalent protein-thiol content compared with control subjects. 5. We conclude that, although release of glutathione from skeletal muscle occurs after excessive contractile activity or inhibition of mitochondrial metabolism, this is not a key step in the damaging processes leading to cytosolic enzyme release, neither is it relevant to the ongoing damage to skeletal muscle which occurs in patients with Duchenne muscular dystrophy.

Topics: 2,4-Dinitrophenol; Animals; Calcimycin; Calcium; Creatine Kinase; Dinitrophenols; Disease Models, Animal; Electric Stimulation; Female; Glutathione; Humans; Muscle Contraction; Muscles; Muscular Dystrophies; Muscular Dystrophy, Animal; Rats; Rats, Inbred Strains; Uncoupling Agents

1. Isolated extensor digitorum longus muscles from control C57BL/10 and mutant dystrophin-deficient C57BL/10 mdx mice have been studied in vitro to determine whether dystrophin deficiency influences the susceptibility of muscle to contractile activity-induced damage. 2. mdx muscles were found to release reduced amounts of intracellular creatine kinase compared with control tissue in response to excessive contractile activity with or without simultaneous stretching of the muscle to 130% of its resting length. 3. In contrast, prostaglandin E2 release from mdx muscle was elevated compared with control tissue in response to either form of contractile activity or to treatment with the calcium ionophore A23187. 4. These results do not support the hypothesis that dystrophin-deficient muscle is more susceptible to damage induced by contractile activity, but suggest that dystrophin deficiency influences the activity of muscle membrane phospholipase enzymes.

Topics: Animals; Calcimycin; Calcium; Creatine Kinase; Dinoprostone; Dystrophin; Mice; Mice, Mutant Strains; Muscle Contraction; Muscles; Muscular Dystrophy, Animal; Phospholipases

Topics: Animals; Calcimycin; Dinoprostone; Dystrophin; In Vitro Techniques; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Muscles; Muscular Dystrophy, Animal; Reference Values