Modulation of mitochondrial adenosine triphosphate-sensitive potassium channels and sodium-hydrogen exchange provide additive protection from severe ischemia-reperfusion injury

Abstract

Background: 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. Methods: Isolated crystalloid-perfused rat hearts (n = 8 hearts per group) were administered vehicle (control, 0.04% dimethyl sulfoxide), diazoxide (100 μmol/L in 0.04% dimethyl sulfoxide), cariporide (10 μmol /L in 0.04% dimethyl sulfoxide), or diazoxide and cariporide before 40 minutes of ischemia at 35.5°C to 36.5°C and 30 minutes of reperfusion. Results: 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 (changepre-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). Conclusions: Combining a selective mitochondrial adenosine triphosphate-sensitive potassium channel opener with a selective reversible inhibitor of sarcolemmal sodium-proton exchange improves recovery of contractile function from severe global ischemia in the isolated buffer-perfused rat heart. The putative mechanism for this benefit is superior protection of mitochondrial function.J Thorac Cardiovasc Surg 2003;125:863-71