Concentration-dependent protective effect of sevoflurane against H₂O₂-induced hypercontracture. (A), Percentage of hypercontracted myocytes measured at 5, 10, and 15 min after exposure to H₂O₂ (100 μm) in the absence and presence of sevoflurane (SEVO) at various concentrations (0.5, 1, 2, 3, and 5%). ** P < 0.01 compared with control at each superfusion time. †† P < 0.01 compared with 0 min in control group, § P < 0.05 and §§ P < 0.01 compared with 0 min in SEVO 0.5% group, ‡ P < 0.01 compared with 0 min in SEVO 1% group. (B) Concentration-dependent prevention of H₂O₂-induced hypercontracture by sevoflurane, measured at 15 min of exposure to H₂O₂ (100 μm). The data points were fitted with a Hill equation: where R is the percentage of hypercontracted myocytes, R₀ is the percentage of hypercontracted myocytes without SEVO, [SEVO] is the millimolar concentration of SEVO, IC₅₀ is the concentration of SEVO causing a half-maximal response, and n_H is Hill coefficient. The smooth curve through the data points represents a least-squares fit, yielding an IC₅₀ of 0.194 mm and n_H of 2.0. The millimolar concentration of SEVO has a linear correlation with the volume percentage (0.5–5%) of SEVO delivered via the vaporizer as follows; (SEVO; in mm) = 0.14592 × (SEVO; in %) − 0.0025182. ** P < 0.01 compared with control. The data shown were obtained from multiple experiments of confocal imaging of fluo-3 fluorescence in ventricular myocytes (N = 3–4) at room temperature (23°–25°C).