Effect of Taurine on Excitation-Contraction Coupling of Extensor Digitorum Longus Muscle of Dystrophic MDX Mouse
Dystrophin is a cytoskeletal protein associated with the sarcolemma. Genetic depletion of the protein leads to Duchenne muscular dystrophy (DMD) and dystrophic conditions in animals such as the mdx mouse9. Mechanical weakness of the sarcolemma during the stress of contraction can account for an abnormal calcium entry in the cell that in turn triggers proteolysis-dependent dystrophic muscle necrosis5,7,9. This mechanism can also account, in a positive feedback loop, for the increased activity of calcium-selective leak ion channels recorded in dystrophinless muscle fibers15. The increased cytosolic calcium is also responsible for longer calcium transients in the dystrophinless fibers7,14, which may affect muscle contractile properties. In skeletal muscle, contraction is triggered mainly by the calcium ions released from the sarcoplasmic reticulum due to depolarization of the sarcolemma and transverse tubules11. Nevertheless, higher cytosolic calcium levels can affect the rate of calcium release and reuptake1,14, thus modifying the excitation-contraction coupling mechanism.
KeywordsSarcoplasmic Reticulum Duchenne Muscular Dystrophy Extensor Digitorum Longus Duchenne Muscular Dystrophy Mechanical Threshold
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- 4.Engel, A.G., Yamamoto, M., and Fischbeck, K.H., 1994, Dystrophinopathies, in: Myology, Engel, A.G. and Franzini-Armstrong, C. eds., Mc Graw-Hill, Inc., New York, Vol. 2, pp. 1133–1187.Google Scholar
- 7.Imbert, N., Cognard, C., Duport, G., Guillon, C., and Raymond, G., Abnormal calcium homeostasis in Duchenne muscular dystrophy myotubes contracting in vitro, Cell Calcium, 18: 177-186.Google Scholar
- 8.Lake, N., 1992, Effects of taurine deficiency on arrhythmogenesis and excitation-contraction coupling in cardiac tissues, in Adv. Exp. Med. Biol. Taurine, Nutritional Value and Mechanism of Action, Lombardini J.B., Schaffer S.W. and Azuma J. eds., Plenum Press, New York, Vol. 315, pp. 173–176.Google Scholar
- 12.Schaffer, S.W and Azuma, J., 1992, Review: myocardial physiological effects of taurine and their significance, in Adv. Exp. Med. Biol. Taurine, Nutritional Value and Mechanism of Action, Lombardini J.B., Schaffer S.W. and Azuma J. eds., Plenum Press, New York, Vol. 315, pp. 105–120.Google Scholar