Effect of ß-adrenergic stimulation and RyR2 phosphorylation on RyR2 gating.

<p>(<b>A</b>) Representative single channel recordings of RyR2 in the presence of cytoplasmic 2 mM ATP and with cytoplasmic [Ca²⁺] at the left of each trace. RyRs were from rat hearts perfused with control buffer (Methods; Traces 1 & 2) or buffer containing 1 µM isoproterenol for 1 min (Traces 3 & 4). Each trace shows a separate experiment. At −40 mV current is downward from the baseline (arrows). (<b>B</b>) Recordings of a RyR2 channel from a 1 min isoproterenol-exposed heart, before and after incubation with cytoplasmic PP1 (7–10 units). Cytoplasmic [Ca²⁺] was 100 nM (Traces 1 & 2) and 10 µM (Traces 3 & 4). (<b>C</b>) Effect of PP1 on RyR2 opening rate at 100 nM Ca²⁺ compiled from 8 experiments like that shown in B (Traces 1 & 2). Four RyRs were used from the control and ISO groups. (<b>D</b>) Opening rate, <i>k_o</i>, mean open duration, <i>T_o</i> and open probability, <i>P_o</i>, of RyR2 at 100 nM Ca²⁺, for control RyR2 treated with PP1, RyR2 from control and isoproterenol treated hearts. Mean values of <i>k_o, T_o</i> and <i>P_o</i> are normalised to their respective means in RyRs from control hearts. Asterisks indicate significant differences from control (p<0.05).