Fig. 2. KCl-induced cytosolic Ca²⁺ transients in isolated FDB fibers from C57BL/6J and mdx^5cv mice recorded in Ca²⁺-free solution. (A) Cytosolic Ca²⁺ transients recorded in C57BL/6J and mdx^5cv fibers in control conditions and in Ca²⁺-free solution containing 1 mM EGTA. (B) Plot of average [Ca²⁺]_i at the base line (b) and at the peak of KCl-induced Ca²⁺ transients (p) for both C57BL/6J and mdx^5cv fibers in control conditions and in Ca²⁺-free solution containing 1 mM EGTA. (C) Plot of average half time of decay of high KCl-induced Ca²⁺ transients in both C57BL/6J and mdx^5cv fibers in control condition and in Ca²⁺-free solution containing 1 mM EGTA. Data come from the fibers analyzed in B. (D) A single mdx^5cv fiber was incubated with Ca²⁺-free solution containing 1 mM EGTA and KCl-induced Ca²⁺ transient was recorded. After 10 minutes, Ca²⁺-free solution was replaced with a solution containing 1.7 mM Ca²⁺, and KCl-induced Ca²⁺ transient was recorded. On the left panel, Ca²⁺ response in Ca²⁺-free solution is superimposed to Ca²⁺ response recorded in Ca²⁺-containing solution. Numbers of fibers tested (from 2 C57BL/6J mice and 2 mdx^5cv mice) are indicated on bar graphs.