MMP9 and ischemia: In all animals (N = 3), bands at the molecular weight of active MMP-9 appeared in gelatin gel zymography and immunoblots by 15 minutes, whereas serine protease bands in the zymography or trypsin levels measured in the immunoblot did not distinctively appear at all during the first hour of ischemia, suggesting MMP release and initial activation in HS did not depend on entry of serine proteases into the circulation.