Creatinine Excretion as An Index of Myofibrillar Protein Mass in Dystrophic Mice

1. Daily creatinine excretion in the urine of normal and dystrophic mice was determined and then the carcass proteins were quantitatively extracted into soluble, myofibrillar and collagenous fractions. 2. on a live body-weight basis, total carcass protein was 15% lower in dystrophic than in normal mice. Relative to carcass weight, however, the amount of protein was significantly lower only in male dystrophic mice. 3. the myofibrillar protein fraction comprised 36.3 and 32.5% of the total protein in male and female dystrophic mice and 48.8 and 45.0% respectively in normal mice. the decrease in myofibrillar protein in dystrophic mice was accompanied by an increase in the residual collagenous fraction of proteins. 4. the rate of excretion of creatinine was strongly correlated (r = +0.98) with the myofibrillar protein mass in each mouse. This relationship was the same for both normal and dystrophic mice, each gram of myofibrillar protein being associated with 3.6 μmol of creatinine excreted/day. 5. the creatinine excretion rate is a valid index of contractile muscle mass in murine dystrophy.

Biochemical changes in progressive muscular dystrophy. XI. Cyclic nucleotides in the skeletal and cardiac muscle of normal and dystrophic mice

cAMP and cGMP contents were determined in the skeletal and cardiac muscle of normal and dystrophic mice. cAMP content increased in the dystrophic muscle at every stage of the disease whereas cGMP content decreased in the preliminary stages and increased at the terminal stage of the disease. The content of both nucleotides per heart was not affected in murine dystrophy. Thus, levels of cyclic nucleotides appear to be selectively altered in dystrophic skeletal muscle.