calcimycin and Muscular-Dystrophies

It is suggested that various muscle diseases and examples of experimentally-induced muscle damage arise because of a high calcium level in the myoplasm. When [Ca2+]i is raised experimentally in amphibian or mammaliam muscle by treatment with A23187 or caffeine, myofilament degradation follows quickly. Such a rapid action suggests the involvement of a sequence of proteolytic activity that is stimulated by a rise in [Ca2+]i. Ca2+ might either trigger protease activity directly or indirectly, or promote the release of lysosomal enzymes. A high [Ca2+]i in dystrophic muscle is believed to be the resultant of a sequence of events that is summarized in the figure. Suggestions are presented for different ways in which the steady-state position of [Ca2+]i might ultimately be controlled for the clinical amelioration of some dystrophic conditions.

Topics: Animals; Caffeine; Calcimycin; Calcium; Cell Membrane; Humans; Magnesium; Muscular Diseases; Muscular Dystrophies; Nucleotides, Cyclic; Osmolar Concentration; Peptide Hydrolases; Sarcoplasmic Reticulum

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

The present study was undertaken to investigate changes in the muscle fiber when treated with calcium ionophore. Muscles treated with ionophore showed disruption of the plasma membrane of the muscle fiber, delta lesions, marked contraction of the myofibrills, and dissolution of Z lines and I bands. Black granules of calcium pyroantimonate were observed inside the plasma membrane in ionophore-treated muscle fibers without alteration of the other muscle organelles. The density of the intramembranous particles was less in muscle treated with calcium ionophore than in the control muscle. These results support the previous hypothesis that the increased concentration of intracellular calcium activates calcium-activated neutral protease and induces necrosis of the myofiber. The mechanism for the decrease in the density of intramembranous particles is unsolved. However, the disruption of the plasma membrane may not be a direct effect of calcium ionophore on it, but a secondary phenomenon which occurs after the calcium-induced necrosis of the muscle fibers.

Topics: Animals; Calcimycin; Calcium; Cell Membrane; Creatine Kinase; Female; Freeze Fracturing; Leupeptins; Microscopy, Electron; Muscles; Muscular Dystrophies; Rats; Rats, Inbred Strains

A number of recent reports suggest that intracellular calcium concentration is increased in skeletal muscle in duchenne muscular dystrophy (DMD). Leucocyte chemiluminescent responses are dependent on calcium ions and can be induced by the calcium ionophore A23187. Chemiluminescence may therefore reflect intracellular calcium levels. In order to determine whether non-muscle cells in DMD share the calcium abnormality, we have examined A23187-induced chemiluminescence in DMD leucocytes. Peak calcium dependent chemiluminescence occurred at 0.25-0.75 mM added calcium chloride. Peak chemiluminescent responses in the 13-paired samples were reduced in DMD leucocytes (P less than 0.01) using a paired t-test. These result suggest that there is an abnormality of calcium dependent A23187-induced chemiluminescence in DMD leucocytes and that there may be a generalised abnormality of calcium metabolism in DMD.

Topics: Anti-Bacterial Agents; Calcimycin; Child; Granulocytes; Humans; Luminescent Measurements; Male; Muscular Dystrophies; Reference Values

Topics: Anti-Bacterial Agents; Calcimycin; Cells, Cultured; Fibroblasts; Humans; Kinetics; Muscular Dystrophies; Proteins; Reference Values; Skin

Rat diaphragms were treated with calcium ionophore, A23187, for 60 min at 37 degrees C, and twitch, tetanus and their derivatives were studied on the basis of the active state concept. Results were than compared with those of human dystrophic muscle. Like dystrophic muscle, maximum tetanic force and maximum velocity of tetanus development were markedly reduced. Changes in twitch parameters, which tend to appear in an early stage of muscular dystrophy, were not noted after the treatment with this ionophore, except alterations relating to prolongation of the active state. Twitch/tetanus ratio was thus increased, while it was decreased in dystrophic muscle. Isoproterenol-induced change of twitch was normally seen in the A23187-treated muscle, while dystrophic muscle responded to catecholamine in a manner different from control. Therefore, the muscle treated with calcium ionophore is not wholly similar to dystrophic muscle.

Topics: Animals; Anti-Bacterial Agents; Calcimycin; Diaphragm; Humans; Isoproterenol; Kinetics; Male; Muscle Contraction; Muscular Dystrophies; Rats; Rats, Inbred Strains

Treatment of red cells from Duchenne muscular dystrophy (DMD) patients with A23187 induced identical responses with those in controls in terms of Ca++ flux, shrinkage, ATP depletion, hypotonic lysis protection, and glycolysis stimulation. The level of RC-free calcium seemed not to be altered in DMD. Valinomycine-induced shrinkage was enhanced significantly in DMD red blood cells.

Topics: Anti-Bacterial Agents; Calcimycin; Calcium; Erythrocytes; Humans; In Vitro Techniques; Muscular Dystrophies; Potassium; Valinomycin

Calcium exchange was studied in skin fibroblasts cultured from eight subjects with Duchenne muscular dystrophy, four with Limb Girdle dystrophy and eight normal controls using 45Ca. No difference was found in the time course of calcium exchange between the groups, nor in the level of 45Ca when maximal exchange had occurred. Treatment of the cultures with the calcium ionophore A23187 resulted in higher levels of calcium exchange over a 2-H period. The increase was similar in the cultures from the 3 patient groups studied.

Topics: Adolescent; Adult; Anti-Bacterial Agents; Calcimycin; Calcium; Cells, Cultured; Child; Child, Preschool; Dimethyl Sulfoxide; Ethanol; Female; Fibroblasts; Humans; Male; Muscular Dystrophies; Skin

Topics: Anti-Bacterial Agents; Calcimycin; Calcium; Child; Child, Preschool; Erythrocyte Membrane; Erythrocytes; Hemolysis; Humans; Muscular Dystrophies; Osmolar Concentration; Potassium; Sodium

Muscle samples for cultures were obtained from the quadriceps by open biopsy under local anesthesia in five patients with early stage of Duchenne muscular dystrophy (DMD) and 10 controls. Primary cultures were grown in Eagle's Minimum Essential Medium (MEM) with 20 per cent fetal calf serum. After 4 weeks, cells were trypsinized, counted, subcultured for 5 days in MEM with 5 per cent horse serum and finally incubated for 4 h with (3H) leucine. Ttal protein synthesis showed a significant decrease (half of control values) only in muscle cultures from patients with DMD. Addition of calclium chloride alone or with A23187 ionophore normalized this defect in protein synthesis. By contrast, myosin heavy chain synthesis was measured and found normal in all paitents.

Topics: Anti-Bacterial Agents; Calcimycin; Calcium Chloride; Cell Count; Child, Preschool; Creatine Kinase; Culture Media; Humans; Infant, Newborn; Muscle Proteins; Muscular Dystrophies; Myosins