FIGURE 4.

Effect of DTDP on spontaneous Ca²⁺ sparks in intact myocyte. (A) The dose dependence and time course of the effect of DTDP on the frequency of spontaneous Ca²⁺ sparks. (B) The reversal effect of DTT. The columns from the left to the right represent the control, 1 mM DTT for >10 min, 30 μM DTDP for 4 min, and the reversal effect of 1 mM DTT, respectively. The results of the last column were obtained from the myocytes, which were exposed to 30 μM DTDP for 5 min and then to 1 mM DTT for >10 min. (C) The distribution curves of F/F₀, FMHM, and FDHM of Ca²⁺ sparks under various conditions. Each curve was obtained from at least 183 sparks; n is the number of the examined myocytes. Versus control, *p < 0.05, **p < 0.01, ***p < 0.001; versus DTDP alone, ^###p < 0.001.