Fig. 7.

Increased frequency of Ca²⁺ sparks in PAH. A Exemplar confocal linescan recordings showing Ca²⁺ sparks (outlined by boxes). B Mean Ca²⁺ spark frequency was significantly increased in MCT cells and was not affected by BB treatment. Myocyte numbers given in the figure. There were no statistically significant difference between the mean C Ca²⁺ spark amplitude, D full width at half-maximum (FWHM) and E duration of the 3 groups. F To estimate the likelihood of a Ca²⁺ spark activating RyR clusters at a neighbouring junction (i.e. spontaneous Ca²⁺ wave initiation), model Ca²⁺ sparks were created using the mean properties of CON, MCT and MCT + BB Ca²⁺ sparks in (C-E). The cytosolic [Ca²⁺] at distances corresponding to the mean resting sarcomere length of each group (dashed line) was calculated. G The peak time-varying RyR open probability (RyR P_o) in the neighbouring junction was greatest in MCT, but was reduced by BB treatment. Data in (G) is normalised to CON. N = 5–8 rats per group, one way ANOVA. *P < .05, **P < .01.