Hereditary Muscular Hypertrophy in the Bovine I. Histological and Biochemical Characterization ∗

Summary

Muscles from three normal calves and three calves with hereditary muscular hypertrophy were biopsied at nine months of age and assayed histochemically for succinic dehydrogenase activity, and histologically for evidence of muscular degeneration. In addition, the biopsy samples were analyzed for total DNA, RNA, and protein. Blood samples from 13 normal and 12 hypertrophied animals were taken at 12 months of age and assayed for creatine phosphokinase activity. Histologically, no degenerative changes were detected in hypertrophied animals. No significant differences were found in concentrations of DNA, RNA, protein, or in serum creatine phosphokinase activity between normal and hypertrophied animals. There was a significant decrease in succinic dehydrogenase activity of the hypertrophied muscle. There were fewer reacting fibers, and the activity was less in those fibers from hypertrophied muscle which did react for succinic dehydrogenase. It is concluded that degeneration is not a part of this syndrome, and that bovine hereditary muscle hypertrophy is associated with a disproportionate number of glycolytic-type fibers. Since these are, on the average, larger than oxidative-type fibers, this observation could explain the gross hypertrophy of the skeletal musculature in this mutant.

The authors are indebted to John Holmes and Henry Stokes for technical assistance, and to Dr. Wade Rollins, Department of Animal Science, University of California, Davis, for making available the animals used in these studies.