Changes of endogenous antioxidant enzymes in cardioprotective effect of isoflurane preconditioning against ischemia/reperfusion injury in isolated rat hearts

Aim To investigate the protective effect of different concentrations of isoflurane preconditioning in isolated rat hearts and the relationship between this effect with changes of endogenous antioxidant enzymes.Methods The isolated SD rat hearts perfused on Langendorff apparatus were randomly divided into 6 groups(n=14):control group(CON);1.44 MAC isoflurane control group(ISO);ischemia-reperfusion group(I/R);3 isoflurane preconditioning groups(I1,I2,I3).All hearts were made globally ischemic for 30 min followed by 60 min reperfusion except CON and ISO.The hearts of ISO and I1,I2,I3 were perfused with K-H solution saturated with 0.72 MAC or 1.08 MAC or 1.44 MAC isoflurane respectively for 20 min followed by 5 min washout after equilibrium.The cardiac function variables were measured after equilibrium,immediately before ischemia,at the end of 30 min and 60 min reperfusion.The infarct size and activities of the endogenous antioxidant enzymes were measured at the end of reperfusion.And the activities of enzymes in I2 group were measured after equilibrium,immediately before ischemia,immediately after ischemia and at the end of 30 min reperfusion.Results Ischemia/reperfusion significantly increased LVEDP and decreased LVDP,dp/dtmax,dp/dtmin and HR(P0.05).Compared with I/R at the end of reperfusion,LVEDP and the infarct size were significantly decreased but HR,dp/dtmax,dp/dtmin and activities of endogenous antioxidant enzymes were markedly increased in I2 and I3 groups(P0.05).After ischemia immediately,the activities of enzymes were markedly lower than equilibrium.During reperfusion period,the activities of endogenous antioxidant enzymes were increased but still lower than equili brium.Conclusion Isoflurane preconditioning can enhance the activities of endogenous antioxidant enzymes,significantly improve cardiac function,reduce myocardial infarct size,and protect the isolated hearts against ischemia/reperfusion injury.