OBJECTIVETo investigate the protective effect of dexmedetomidine (Dex) preconditioning against ischemia/reperfusion (I/R) injuries in isolated rat hearts and its relation to mitochondrial permeability transition pore (mPTP) and mitochondrial ATP-sensitive K(+) channel (mitoKATP).

METHODSThe hearts of male SD rats were isolated to mount on the Langendorff apparatus and subjected to 30 min global ischemia followed by 120 min reperfusion. The isolated hearts were treated with Dex (10 nmol/L) before ischemia for 15 min. The left ventricular hemodynamic parameters,coronary flow (CF) and the lactate dehydrogenase (LDH) release in the coronary effluent at 5 min reperfusion were measured. The formazan content was assayed to determine the myocardial viability at the end of reperfusion.

RESULTSCompared with normal controls, I/R markedly decreased the left ventricular developed pressure and CF during the whole reperfusion period and the formazan content; while the left ventricular end diastolic pressure and LDH release were significantly increased. Dex preconditioning markedly improved the myocardial viability and cardiac function (P<0.01), which were reversed by the treatment with both atractyloside (20 μmol/L before ischemia), an opener of mPTP, and 5-hydroxydecanoate (100 μmol/L at the beginning of reperfusion), an inhibitor of mitoKATP, for 20 min.

CONCLUSIONDex has protective effect against I/R injuries in isolated rat hearts, which may be related to inhibiting the opening of mPTP at the beginning of reperfusion and activating mitoKATP before ischemia.