['Preconditioning and inhibition of sodium-proton exchange attenuate myocardial ischemia-reperfusion injury by means of independent mechanisms that might act additively when used together. The hypothesis of this study is that treatment with a sodium-proton exchange inhibitor and a mitochondrial adenosine triphosphate-sensitive potassium channel opener produces superior functional recovery and a greater decrease in left ventricular infarct size compared with treatment with either drug alone in a model of severe global ischemia.', 'Isolated crystalloid-perfused rat hearts (n = 8 hearts per group) were administered vehicle (control, 0.04% dimethyl sulfoxide), diazoxide (100 micromol/L in 0.04% dimethyl sulfoxide), cariporide (10 micromol /L in 0.04% dimethyl sulfoxide), or diazoxide and cariporide before 40 minutes of ischemia at 35.5 degrees C to 36.5 degrees C and 30 minutes of reperfusion.', 'The combination group had superior postischemic systolic function compared with that seen in the cariporide, diazoxide, and control groups (recovery of developed pressure: 91% +/- 7% vs 26% +/- 5%, 35% +/- 6%, and 16% +/- 3%, respectively; P <.05). Postischemic diastolic function in the combination group was superior compared with that seen in the other groups (change(pre-post) diastolic pressure of 67 +/- 4 mm Hg with control, 49 +/- 11 mm Hg with diazoxide, 59 +/- 10 mm Hg with cariporide, and 3 +/- 3 mm Hg with diazoxide and cariporide combination; P <.05). The left ventricular infarct area was less in the combination group compared with that in the cariporide, diazoxide, and control groups (6% +/- 2% vs 35% +/- 7%, 25% +/- 3%, and 37% +/- 9%, respectively; P <.05).'] Do modulation of mitochondrial adenosine triphosphate-sensitive potassium channels and sodium-hydrogen exchange provide additive protection from severe ischemia-reperfusion injury?