Abstract: AIM: To investigate the changes of myocardial NO levels and the expression of NOS isoforms in rats with myocardial ischemia reperfusion (MIR) and the protective effect of anti-digoxin antiserum, an digoxin specific antagonist, on MIR induced NO system injury.METHODS: Myocardial ischemia reperfusion injury models were made by ligating the left anterior descending coronary artery for 30 min and followed by 45min reperfusion.Sprauge-Dawley rats were randomly divided into seven groups each with 10 rats including sham group, MIR group, normal saline group, verapamil group, low dose, middle dose and high dose anti-digoxin antiserum groups.The NO levels of myocardial and serum, activities of eNOS and iNOS were measured.The expression of myocardial eNOS and iNOS were determined by immunohistochemisry. The myocardial morphology was observed under optical microscope.RESULTS: The myocardial NO levels were significantly increased;The serum NO levels did not changed significantly;The eNOS expression were significantly decreased;The iNOS expression were significantly increased.Meanwhile, myocardial morphology injury was remarkable.With the intervention of middle and high dose anti-digoxin antiserum, the expression of myocardial iNOS were significantly depressed, the eNOS expression were reverted, the serum and myocardium NO levels were significantly increased.The myocardial histological morphology was significantly improved.CONCLUSION: The anti-digoxin antiserum can protect the function of myocardial NO system against MIR.The mechanism maybe antagonize endoxin and regulate the expression of NOS isoforms in myocardium.

Key words: endogenous digitalis-like factor, ischemical reperfusion injury, myocardium, NOS, antidigoxin antiserum