Figure 3.

Continued exposure to high concentrations of H₂O₂ increases the thresholds for SOICR. HEK293 cells stably expressing RyR2 were transfected with the luminally expressed FRET-based Ca²⁺ indicator; D1ER. The cells were superfused with KRH containing 1 or 2 mM Ca²⁺ with or without H₂O₂ (1 mM). At the end of each experiment cells were perfused with 20 mM caffeine to illustrate functional RyR2 channels. Representative traces of cells exposed to (A) 0 or (B) 1 mM H₂O₂; dashed lines represent the release (before: F_SOICR and after: F_SOICR^∗ H₂O₂) and termination (before: F_Termi and after: F_Termi^∗ H₂O₂) SOICR thresholds. F_Inhib (B) represents the store level after SOICR was inhibited by H₂O₂.