Influence of CD39 on cardiac ischemia-reperfusion injury. CD39^−/− or littermate controls matched by age and sex (CD39^+/+) were exposed to 15 to 60 minutes of coronary ischemia via in situ ligation of the left coronary artery and were killed after 2 hours of reperfusion. Infarct sizes were measured by double staining with Evan blue and 2,3,5-triphenyltetrazolium chloride (TTC). (A) Representative images of infarcts from the experiment are displayed (blue represents retrograde Evan blue staining; red and white, area at risk; white, infarcted tissue). (B) Infarct sizes expressed as the percentage of the area at risk that underwent infarction (mean ± SD, n = 6). *P < .05 compared to wild-type mice (cd39^+/+).