The cardioprotective effect of MIF20 requires endogenous MIF and the cell surface MIF receptor, CD74. Heart rate-left ventricular developed pressure product during baseline perfusion, ischemia and post-ischemic reperfusion of MIF-KO hearts (A) and CD74-KO hearts (B) treated with or without MIF20 (8 nM) prior to ischemia (n=4 hearts for each group, P=NS). (C) Representative western blots of cardiac AMPK phosphorylation 30 mins after initiation of reperfusion in WT, MIF-KO, and CD74-KO hearts treated with vehicle or MIF20 (8 nM). Two representative tissue lysates are shown by western blotting and densitometry shows the mean + SEM for 4 hearts for each experimental group. *p<0.05 vs. WT vehicle.