Aim:To examine if isoflurane preconditioning can attenuate ischemia/reperfusioninjury by reducing cytochrome c release from inner mitochondrial membrane.Methods:Isolated hearts of Sprague-Dawley rats were perfused on Langendorffapparatus.Hearts were randomly assigned to a non-treated group(CON group,n=12)or three isoflurane preconditioning groups(0.5% ISC group,1.0% ISC group,and 2.0% ISC group;n=12).In the latter three groups,isoflurane was given atconcentrations of 0.5%,1.0%,and 2.0% for 15 min with 15-rain washout before30-min ischemia.Subsarcolemmal mitochondria of the myocardium were isolatedafter 60-min reperfusion.Hemodynamics of the each heart was recorded,infarctsize of the hearts and contents of cytosolic cytochrome or mitochondrial cyto-chrome c were measured at the end of reperfusion.Morphology of isolated mito-chondria in the four groups was evaluated,respectively.Results:Compared withthe CON group,cytosolic cytochrome c in 0.5% ISC group,1.0% ISC group,and2.0% ISC group were significantly decreased along with a significant increase ofmitochondrial cytochrome c.Infarct size of the hearts in the four groups were56%±12%,41%±12%,32%±7% and 33 %±11%,respectively.The values of thethree isoflurane preconditioning groups were significantly lower than that of theCON group(P<0.05).Isoflurane exposure before ischemia can attenuate the changeof morphology of mitochondria after reperfusion.The effects of 2.0% isofluraneon reducing cytochrome c release were more remarkable than 0.5% and 1.0%concentrations of isoflurane.Conclusion:Myocardioprotective effects ofisofluranc preconditioning were associated with attenuation of cytochrome c lossfrom the inner membrane of subsarcolemmal mitochondria. Aim: To examine if isoflurane preconditioning can attenuate ischemia / reperfusioninjury by reducing cytochrome c release from inner mitochondrial membrane. Methods: Isolated hearts of Sprague-Dawley rats were perfused on Langendorffapparatus. Hearts were randomly assigned to a non-treated group (CON group, n = 12) or three isoflurane preconditioning groups (0.5% ISC group, 1.0% ISC group, and 2.0% ISC group; n = 12) .In the latter three groups, isoflurane was given at concentrations of 0.5%, 1.0%, and 2.0 % for 15 min with 15-min washout before 30-min ischemia. Subarcolemmal mitochondria of the myocardium were isolated after 60-min reperfusion. Hemodynamics of the each heart was recorded, infarctsize of the hearts and contents of cytosolic cytochrome or mitochondrial cyto-chrome c were measured at the end of reperfusion. Morphology of isolated mito-chondria in the four groups was evaluated, respectively. Results: Compared with the CON group, cytosolic cytochrome c in 0.5% ISC group, 1.0% ISC group, and 2.0% ISC group w ere significantly decreased along with a significant increase of mitochondrial cytochrome c. Infarct size of the hearts in the four groups were 56% ± 12%, 41% ± 12%, 32% ± 7% and 33% ± 11% respectively. The values ​​of thethree isoflurane preconditioning groups were significantly lower than that of theCON group (P <0.05). Isoflurane exposure before ischemia can attenuate the change of morphology of mitochondria after reperfusion. the effects of 2.0% isofluraneon reducing cytochrome c release were more remarkable than 0.5% and 1.0 % concentrations of isoflurane.Conclusion: Myocardioprotective effects of isofluranc preconditioning were associated with attenuation of cytochrome c loss from the inner membrane of subsarcolemmal mitochondria.