Dynamic changes of the concentration of nitric oxide in ischemic myocardium and its mechanism

AIM: The study was undertaken to explore the dynamic changes of the concentration of nitric oxide(NO) in ischemic myocardium and its mechanism.METHODS: In vivo myocardial ischemia of mice and in vitro perfused isolated heart of rat were used in the experiment. The effects of severity and time of ischemia on NO production, NOS activity and mRNA were examined, respectively. RESULTS: There was a considerable difference (P<0.01) in the concentration of NO between ischemia group [(9.12±1.40) μmol/L] and control group [(20.16±1.67) μmol/L] after Pit(30 U/kg) administration, and the concentration of NO of ischemic group significantly decreased [(9.17±1.33) μmol/L] compared with control group [(19.90±1.95) μmol/L] after 30 minutes of ischemia. Also, the concentration of NO after Pit(20 U/L) administration in K-H and 15 min of ischemia was (15.41±2.00) μmol/L and (15.09±2.00) μmol/L respectively in vitro, significantly lower than control group [(23.83±2.33) μmol/L and (23.63±2.52) μmol/L]. In addition, compared with control group, the number of NOS positive cells, NOS activity as well as mRNA expression in atrial muscle and ventricular muscle of ischemic group were markedly reduced, respectively. CONCLUSION: Myocardial ischemia could reduced the NO level in myocardium, down-regulation of NOS mRNA could be the possible mechanism.