Activation of the Na+/Ca2+ exchanger may contribute to Ca2+ overload during 
reperfusion after transient ischemia. We examined the effects of 
2-[4-[(2,5-difluorophenyl) methoxy]phenoxy]-5-ethoxyaniline (SEA0400), a 
selective inhibitor of Na+/Ca2+ exchange, on a canine model of 
ischemia/reperfusion injury (myocardial stunning). Myocardial stunning was 
induced by a 15-min occlusion of the left anterior descending coronary artery 
followed by a 4-h reperfusion in anesthetized open-chest dogs. Reperfusion 
gradually restored myocardial percent segment shortening but remained depressed 
during a 4-h reperfusion period. A bolus intravenous injection of SEA0400 (0.3 
or 1.0 mg/kg), given 1 min before reperfusion, improved significantly the 
recovery of percent segment shortening in the ischemic/reperfused myocardium. 
SEA0400 did not affect the hemodynamics and electrocardiogram parameters. In 
addition, SEA0400 did not affect reperfusion-induced change in coronary blood 
flow. These results suggest that the Na+/Ca2+ exchanger is involved in the 
stunned myocardium of dogs after reperfusion, and that SEA0400 has a protective 
effect against myocardial stunning in dogs.