Isoflurane preconditioning is abolished in miR-21 knockout mice. Wild-type (WT) and miR-21 knockout mice were exposed to 30 min of coronary artery occlusion followed by 2 h of reperfusion with and without isoflurane exposure. (A) Area at risk measurements. There were no significant differences between area at risk in control or isoflurane-exposed WT and miR-21 knockout mice. n = 8/group. (B) Isoflurane preconditioning is abolished in miR-21 knockout mice. WT mice were successfully preconditioned with isoflurane, while miR-21 knockout mice showed no significant difference between control and isoflurane-exposed groups. n = 8/group, *P < 0.05.