Isoflurane (ISO)-induced improvements in cardiac function were blocked by disruption of microRNA-21 (miR-21) gene in Langendorff-perfused hearts subjected to 30 min of global ischemia followed by 2 h of reperfusion. (A) +dP/dt (maximum rate of increase of left ventricular developed pressure). (B) −dP/dt (maximum rate of decrease of left ventricular developed pressure). In the wild-type (WT) (C57BL/6 heart) Time-C (time control) and miR-21 knockout (KO) Time-C groups, the hearts were perfused in Langendorff apparatus for 210 min, whereas in the other groups, all hearts were stabilized for 30 min (baseline) and perfused with the buffer with or without ISO before 30 min of global ischemia followed by 2 h of reperfusion. ISO was administered by two cycles of 5-min ISO/5-min washout followed by a period of 10-min washout. *P < 0.05 versus WT-I/R; #P < 0.05 versus WT-I/R+ISO (n = 7 to 9 hearts per group). I/R = ischemia–reperfusion.