Fig. 4. Activation of mitochondrial adenosine triphosphate-sensitive potassium channel is important during both preconditioning by isoflurane and exposure to oxidative stress. ( A ) Myocyte protection by isoflurane (APC vs . stress) was abolished in the presence of 5-hydroxydecanoic acid (APC + 5-HD). 5-HD alone did not affect cell death in nonpreconditioned myocytes (stress + 5-HD) or in time control (TC + 5-HD). * P < 0.05 versus stress, stress + 5-HD, and APC + 5-HD. All values were significantly different versus TC + 5-HD. ( B ) Blockade of mitochondrial adenosine triphosphate-sensitive potassium channel during both isoflurane pretreatment (APC + 5-HDISO) and oxidative stress (APC + 5-HDstress) completely abolished isoflurane-induced protection. * P < 0.05 versus stress, APC + 5-HDISO, and APC + 5-HDstress.