Three months post-tamoxifen, echocardiography at baseline (time 0), then 1, 2, 3, 4 and 5 minutes after isoproterenol injection (0.4 μg/kg) was used to analyze A) ejection fraction (EF) and B) fractional shortening (FS). A) EF at minute 5: MCM+(black line): 80.58% ± 6.19, Emrefl/fl (purple line): 81.62% ± 5.69 and EmrecKO (green line): 70.20% ± 11.08. B) FS at minute 5: MCM+: 48.42% ± 6.32, Emrefl/fl: 49.80% ± 5.67 and EmrecKO: 39.58% ± 9.14. Values represent mean ± SD. *p<0.05, n=10–12 per group. Two-way ANOVA was used for statistical analysis. Three months post-tamoxifen, mouse hearts were subjected to 20 minutes of stabilization, 20 minutes of global ischemia and 90 minutes of reperfusion. At 5, 30, 60, and 90 minutes after the onset of reperfusion, relative to baseline pre-ischemia, C) rate pressure product (RPP) = heart rate (HR) × left ventricular pressure (LVP), D) dP/dtmax, E) dP/dtmin, and F) creatine kinase (CK) release were assessed. Values represent mean ± SD. *p<0.05, n=5–6 per group. Two-way ANOVA was used for statistical analysis.