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Figure 3 Effects of intramyocardial plasminogen activator inhibitor type 1 (PAI-1) deoxyribonucleic acid (DNA) enzyme injection on myocardial PAI-1 messenger ribonucleic acid (mRNA) and protein expression. (a) Results of reverse transcription-polymerase chain reaction (RT-PCR) 48 h after left anterior descending coronary artery (LAD) ligation and direct injection of DNA enzymes at the peri-infarct region (PIR), showing reduced myocardial PAI-1 mRNA expression after E2 injection relative to E0 (p < 0.01, n = 6 to 10). (b) Immunohistochemical staining (IHC) analysis of normal rat myocardium and rat PIR 48 h after LAD ligation. (Left) The PAI-1 expression in rat cardiomyocytes of animals treated with E0, but not with E2. PAI-1 positively stained cells were visualized as brown with immunoperoxidase technique and 3,3'-diaminobenzidine tetrahydrochloride substrate. (Right) quantitative IHC analyses showing reduced numbers of PAI-1 expressing cells at the PIR after E2 injection relative to E0 (p < 0.01, n = 6 to 10). (c) The RT-PCR analyses 2 weeks after LAD ligation and direct injection of E2 at the PIR, showing reduced level of PAI-1 mRNA in infarcted left ventricles after E2 injection relative to saline (p < 0.01, n = 6 to 10).