Calmodulin content and Ca-activated protease activity in dystrophic hamster muscles

As part of a study on the implication of elevated Ca2+ levels in the myofibrillar degeneration seen in dystrophic muscle, the content of calmodulin and the activity of Ca2+-activated neutral protease (CANP) have been measured in normal and dystrophic (UM-X7.1) hamsters. Calmodulin levels, expressed as micrograms +/- SEM per gram wet weight were highest in brain (385 +/- 24.7), followed by tongue (93.88 +/- 3.93), heart (42.13 +/- 2.93), and skeletal muscle (31.69 +/- 1.42). No significant increases in calmodulin were observed in the dystrophic tissues thus suggesting that the Ca2+ accumulations observed in dystrophic muscles are unrelated to changes in a calmodulin levels. Because of the complexity of regulation of CANP, a time-dependent study was done using extracts of skeletal, heart, and tongue muscles. Marginal increases in dystrophic CANP were seen in skeletal muscle at all times studied and in the heart and tongue at initial time points only. The data are discussed in terms of rising levels of Ca2+ in muscles of the UM-X7.1 hamster being sufficient to increase CANP activity (without increasing content) to where it causes Z-line dissolution.