Poloxamer 188 reduces the contraction-induced force decline in lumbrical muscles from mdx mice

1 Department of Biomedical Engineering, 2 Department of Molecular and Integrative Physiology, and 3 Department of Surgery, Section of Plastic Surgery, University of Michigan, Ann Arbor, Michigan Submitted 11 January 2008 ; accepted in final form 16 May 2008 Duchenne Muscular Dystrophy is a genetic disease caused by the lack of the protein dystrophin. Dystrophic muscles are highly susceptible to contraction-induced injury, and following contractile activity, have disrupted plasma membranes that allow leakage of calcium ions into muscle fibers. Because of the direct relationship between increased intracellular calcium concentration and muscle dysfunction, therapeutic outcomes may be achieved through the identification and restriction of calcium influx pathways. Our purpose was to determine the contribution of sarcolemmal lesions to the force deficits caused by contraction-induced injury in dystrophic skeletal muscles. Using isolated lumbrical muscles from dystrophic ( mdx ) mice, we demonstrate for the first time that poloxamer 188 (P188), a membrane-sealing poloxamer, is effective in reducing the force deficit in a whole mdx skeletal muscle. A reduction in force deficit was also observed in mdx muscles that were exposed to a calcium-free environment. These results, coupled with previous observations of calcium entry into mdx muscle fibers during a similar contraction protocol, support the interpretation that extracellular calcium enters through sarcolemmal lesions and contributes to the force deficit observed in mdx muscles. The results provide a basis for potential therapeutic strategies directed at membrane stabilization of dystrophin-deficient skeletal muscle fibers. muscular dystrophy; sarcolemmal lesions Address for reprint requests and other correspondence: J. A. Faulkner, Univ. of Michigan, BSRB, Rm. 2035, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200 (e-mail: jafaulk{at}umich.edu )