Alteration of Sarcoplasmic Reticulum Ca²⁺ Release in Skeletal Muscle from Calpain 3-Deficient Mice

Figure 6

Effect of caffeine on [Ca²⁺]_i in isolated myotubes in the presence of Ca²⁺ channel blockers (Ni²⁺/Cd²⁺). Representative traces show the typical time course of the response to 20 mM caffeine observed in (a) wild type (+/+) myotube; (c) calpain 3-deficient (−/−) myotube, each treated with Ni²⁺/Cd²⁺. The duration of exposure to caffeine (open bars), or 50 𝜇M Ni²⁺/100 𝜇M Cd²⁺ (closed bars) is represented. Bar diagrams (b) and (d) summarize the peak amplitude of the [Ca²⁺]_i response of myotubes to caffeine and CPA. The responses from the wild type myotubes (+/+; b) and calpain 3-deficient myotubes (−/−; d), are shown. Fifty 𝜇M Ni²⁺/100 𝜇M Cd²⁺ was added to the extracellular medium prior to the second application. The number of cells tested is given in brackets.

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(b)

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(d)