Growth and Development of Skeletal Muscle in μ‐Calpain Knockout Mice

The calpain system has been identified as a potential candidate in muscle growth and development due to its role in a variety of cellular processes such as cytoskeletal remodeling and myogenesis. The objective of this study was to evaluate growth and development of skeletal muscle in μ‐calpain knockout mice (KO) compared to wild type C57/BL6 mice (WT). At 3, 5, 10, 20 and 30 weeks of age WT and KO mice (n=6) were sacrificed and extensor digitorum longus (EDL), tibialis anterior (TA), quadriceps, gastrocnemius and soleus muscles were quantitatively dissected. Body composition was evaluated by proximal analysis on WT and KO mice (n = 6) for each age group. Muscle weights and total RNA, DNA and protein were unaffected by genotype. At 30 weeks there was an increased potential for protein synthesis and muscle hypertrophy in the KO mice as indicated by the increased protein:DNA ( P = 0.0349) and RNA:DNA ( P = 0.016). This is reflected in the body composition analysis, which showed KO mice had increased protein content at the expense of lipid content at 30 weeks ( P = 0.0102). These data suggests the calpain system is involved in muscle growth and appears to be involved in muscle wasting at 30 weeks of age.