Development of changes in cation content of muscles from the 129 ReJ dystrophic mouse

1. Muscle cation levels have been measured in severely affected and relatively unaffected muscles of dystrophic mice (129 ReJ strain) compared to control animals at various ages. 2. Muscle calcium levels were found to be elevated in the severely affected gastrocnemius muscles only at a late stage of the disease, calcium levels in mildly affected triceps muscles were unaffected. 3. Muscle sodium levels were elevated in both triceps and gastrocnemius muscles at all ages studied. 4. Muscle magnesium and potassium contents showed similar changes, being significantly reduced in the gastrocnemius from the time of development of the first signs of weakness (i.e. 3-5 weeks of age), this decrease becoming more marked with increasing age and showing a less marked, but significant, change in the triceps muscle at a later stage of the disease.