Energy status of cells lacking dystrophin: an in vivo/in vitro study of mdx mouse skeletal muscle.

Although great strides have been made in understanding the genetics of Duchenne muscular dystrophy (DMD), uncertainty still remains as to the metabolic changes which are associated with the disease. We have used the recently discovered animal model of DMD, the mdx mouse, to study aspects of high energy phosphate metabolism and metabolic control indices in dystrophic muscle. This model of DMD has the dual advantage of having a genetic defect which is homologous to that in human DMD, and it lacks the fatty infiltration and necrosis which makes biochemical analysis of DMD so difficult. We have used nuclear magnetic resonance spectroscopy (NMR) to monitor developmental changes in high energy phosphates and pH. No differences were observed between young (less than 40-50 days old) control and mdx mice. The pH increase and alterations in phosphate ratios (i.e., a decline in PCr/ATP) observed in adult mdx vs. control mice are qualitatively similar to those observed in humans. Biochemical analysis showed a small decline in ATP and PCr content and a decline in some indices of energy status in adult mdx mice. As young mdx mice appeared to be normal, the lack of dystrophin does not correlate with metabolic changes. The changes which were observed were small enough that alterations in fibre composition could be the major contributory factor.