Using reaction-diffusion modeling, we have previously shown that the rise time of signal mass equals the duration of ICa(spark) (ZhuGe et al., 2000). As shown in Fig. 1 B, the rise time of signal mass is the same as TTODSTOC (Fig. 1 B); we reason that TTODSTOC should reflect the duration of ICa(spark). Therefore, by examining the relationship between TTODSTOC and STOC amplitude, we can infer the relationship between the duration of ICa(spark) and the magnitude of STOCs. Fig. 3 B demonstrates that there was a positive correlation between TTODSTOC and STOC amplitude for the events shown in Fig. 2 A (r = 0.5561, P = 0.0001). This correlation is also evident in the averaged data in which STOCs were divided into quartiles based on their rank order of TTODSTOC; i.e., the longer the TTODSTOC, the greater the STOC amplitude (ANOVA, P < 0.05). Therefore, the duration of ICa(spark) contributes to the amplitude of STOCs. This relationship implies that (a) activation kinetics plays a role in determining the amplitude of STOCs and (b) additional recruitment of BK channels is possible
