Maximum rate of Mn²⁺ quench in the presence or absence of store depletion. (A and B) Representative traces of fura-2 fluorescence during application of 0.5 mM Mn²⁺ in FDB fibers isolated from WT and CASQ1-null mice following prior store depletion induced with 1 µM TG + 15 µM CPA (A; +depletion) and in the absence of store depletion (B; −depletion). (C and D) Quantitative analyses of the maximum rate of Mn²⁺ quench in the presence (C) and absence (D) of prior store depletion. (E and F) Frequency histograms of the percentage of FDB fibers exhibiting different levels of maximum rate of Mn²⁺ quench in the presence (E) and absence (F) of prior store depletion. Histogram data were fit with a single Gaussian distribution. Data are shown as mean ± SEM; *, P < 0.05. Numbers in bars (n) indicate the number of FDB fibers analyzed. Number of mice: n = 6 WT; n = 5 CASQ1-null.