Lack of prolonged reperfusion in our experimental design may explain this discrepancy, because it has been reported that the protein levels of VEGF after ischemia (without reperfusion) are comparable to the untreated control but are increased two and three folds after 4 h or 8 h of reperfusion, respectively (Mu et al., 2003), indicating that VEGF protein is produced in the reperfusion stage and the ischemia duration may only stimulate the HIF-1α-mediated VEGF mRNA expression, while may not be long enough to induce VEGF protein synthesis. Here, HIF1A is linked to ischemia.