FIGURE 4.

Effect of Pi on PTP opening induced by Ca²⁺. Experimental conditions were as indicated in Figure 1. (A) ΔΨ was monitored with 5 μM safranine O as fluorescence decrease; (B) CRC was evaluated with 0.5 μM calcium green-5N as fluorescence increase. Where indicated, 5 mM succinate-Tris (Succ) and 80 μM Ca²⁺ pulses in sequence were added. In traces a (controls), 1 mM Pi-Tris was added; in traces b, no Pi-Tris was present. (C) Isolated CM were incubated as in Figure 1, and Ca²⁺ was added to induce PTP opening, measured as fluorescence change of 0.5 μM calcium green-5N, in the presence of increasing concentrations of Pi-Tris.