IN-VIVO EVIDENCE OF ABNORMAL MECHANICAL AND OXIDATIVE FUNCTIONS IN THE EXERCISED MUSCLE OF DYSTROPHIC HAMSTERS BY P-31-NMR

Mechanical properties and metabolic adaptation to exercise in skeletal muscle of dystrophic hamsters were studied with an in vivo P-31-NMR m ultistep fatigue test. Three successive 20-min steps with increasing r hythms of tetanic stimulation were followed by a 20-min recovery perio d. Fatigue in dystrophic hamsters (DH) developed more rapidly and was greater than in normal hamsters (NH); total mechanical performance per min increased step by step in NH while it decreased in DH, showing a progressive mechanical impairment of the dystrophic muscles. ADP and P Cr recovery rates were significantly reduced in DH muscles. Acidosis a ppeared in both DH and NH and persisted in DH throughout the test, sug gesting reduced mitochondrial oxidative capacity of the dystrophic mus cle. The pH recovery rate was reduced in DH muscles suggesting a reduc tion in export protons capacity. These results provide evidence of imp aired mitochondrial function and intracellular ionic regulation in the dystrophic muscle, associated with the lack of dystrophin and dystrop hin-associated glycoproteins in the DH.