Regulation of RyR2 open probability by cytoplasmic Ca²⁺ and Mg²⁺.

<p>RyRs from control (•, n = 3–8) and 1 min isoproterenol stimulated hearts (○, n = 3–9). All recording solutions contained 2 mM ATP. (<b>A</b>) Dependence of open probability on cytoplasmic [Ca²⁺]. (<b>B</b>) Dependence of normalised open probability on cytoplasmic [Mg²⁺] in the presence of 10 µM cytoplasmic Ca^2<b>+</b>. (<b>C</b>) Cytoplasmic Ca²⁺ activation of <i>P_o</i> in the presence of 1 mM cytoplasmic Mg²⁺ and 1 mM luminal Ca²⁺. Asterisks indicates significant differences between • and ○ (p<0.05). Solid and dashed curves show fits of the RyR2 gating model to the control and isoproterenol data, respectively.