Figure 12. Delay of [Ca²⁺]_m compared with [Ca²⁺]_c.

A, delay of cell contraction (ΔL) after depolarization-induced changes in cytosolic calcium concentration, [Ca²⁺]_c (expanded version of part of Fig. 8). Note the oscillating peaks of [Ca²⁺]_c, recorded by indo-1 fluorescence, precedes that of ΔL. The latency of ΔL is about 200 ms. Since Ru360 blocks mitochondrial Ca²⁺ uptake, F₄₀₀/F₅₀₀ reports only cytosolic Ca²⁺. There was no Mn²⁺ in the bath but 0.2 μm Ru360 in the pipette to block mitochondrial Ca²⁺ uptake. B, delay of mitochondrial [Ca²⁺]_m after depolarization-induced cell contraction in another ferret cell without Ru360. Note the depolarization-induced [Ca²⁺]_m is preceded by cell contraction (shown as percentage of resting cell length, RCL). The latency of [Ca²⁺]_mvs. contraction was 0.8 s. Addition of the 200 ms delay between [Ca²⁺]_c and contraction (A) makes the total delay of [Ca²⁺]_mvs.[Ca²⁺]_c about 1 s. Mn²⁺ (0.7 mm) was in the bath to quench cytosolic indo-1.