Background
Nitric oxide (NO) is protective for the cardiovascular system, and excessive NO exerts negative effects on the circulatory system. This study aimed to compare the effects of selective or non-selective NO synthase (NOS) inhibitors on blood flow perfusion of ischemia-reperfused myocardium.
Material and Methods
Male mongrel dogs were randomly assigned to 4 groups: only ischemia-reperfusion (control), ischemia-reperfusion plus Nù-nitro-L-arginine methyl ester (NAME) treatment, ischemia-reperfusion plus aminoguanidine (AMD) treatment, and sham operation group. Myocardial contrast echocardiography (MCE) was performed. Blood samples were taken for measurement of NO. Background-subtracted peak videointensity (PVI) and PVI ratio in myocardium were measured.
Results
In the NAME-treated group, the PVI at 5 min reperfusion did not significantly differ from pre-LAD-occlusion, but declined to and retained at a level obviously lower than the pre-LAD-occlusion. In the AMD-treated group, the PVI at 5 min reperfusion was significantly higher than at pre-LAD-occlusion, and then restored to and remained at the pre-LAD-occlusion level. The changes of PVI ratios in the 3 groups were similar to PVI values. In the AMD-treated group, the curve width increased in the early reperfusion, but returned to the pre-LAD-occlusion level at 90 min reperfusion. The plasma NO concentration in the NAME-treated group greatly decreased and remained low during the whole period of reperfusion. In the AMD-treated group, there were only slight increases in NO concentrations during reperfusion.
Conclusions
NAME totally inhibited NO production and attenuated myocardial blood flow perfusion. Aminoguanidine significantly relieved the increase in NO production and alleviated the congestion of reperfused myocardium. Selective inhibitors of iNOS might be useful in the management of certain diseases associated with ischemia-reperfusion.

Keywords: Myocardium - pathology, Myocardial Reperfusion Injury - ultrasonography, Hemodynamics - drug effects, Enzyme Inhibitors - therapeutic use, Dogs, Coronary Sinus - physiopathology, Nitric Oxide - blood, Nitric Oxide Synthase - metabolism, Perfusion