To quantify protected effect of norepinephrine (NE) induced delayed phase of ischemic preconditioning

the relationship between cardioprotection and superoxide dismutase(SOD) was studied. A total of 50 rats were randomly divided into three groups:NE group

I/R group and normal group

3.1 μmol/kg NE was injected into abdomen 24 hours before surgery as a trigger

both NE and I/R group underwent main left coronary artery occlusion for 30 minutes then reperfusion for 120 minutes. Ischemic risk area

infarct area and nonischemic area were identified by TTC

Evan’ s blue staining methods and calculated by Metamorph Imaging System software. Serum Cu 2+

Cytosol Cu 2+

Zn 2+-SOD content and activity

and activity of mitochondrial Mn-SOD activity were detected by radioimmunoassay and method xanthosine oxidase separately. Results showed that: 1) infarct size was reduced by 33.4% in preconditioned heart; 2) mitochondrial Mn-SOD activity was higher in preconditioned myocardium; 3) no significant difference about the activity and content of Cu 2+

Zn 2+-SOD either in serum or in myocardium was found. The above phenomena imply that preconditioned cardioprotection might be only related to mitochondrial Mn-SOD

mitochondrial Mn-SOD might be the final effector of NE induced preconditioning .