Fig. 1. KCl-induced cytosolic Ca²⁺ transients in isolated FDB fibers from C57BL/6J and mdx^5cv mice. (A,B) Calcium transients evoked by pressure ejection of a high KCl solution in isolated C57BL/6J and mdx^5cv fibers, respectively. Top panels in A and B show time series of pseudocolor F₃₄₀/F₃₈₀ ratio images of isolated C57BL/6J and mdx^5cv fibers, respectively. Bottom panels represent global cytosolic Ca²⁺ transients triggered by high-KCl calculated from the whole fiber perimeter. Red circles on curves correspond to recording time of the 18 ratio images in both cases. (C) 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. (D) Plot of average half time of decay of KCl-induced Ca²⁺ transients in both C57BL/6J and mdx^5cv fibers analyzed in C. Numbers of fibers tested (from six mice for C57BL/6J fibers and from 10 mice for mdx^5cv fibers) are indicated on bar graphs.