Overexpression of endothelium nitric oxide restores relaxation in the hindlimb vasculature after myocardial infarction

After myocardial infarction (MI), NO-mediated vasorelaxation is attenuated in both large and resistance arteries. The mechanisms of this depression are unclear. To determine if the attenuated vasorelaxation after MI is due to downregulation of eNOS protein, immunoblotting and gene transfer of eNOS was performed using a "first-generation" serotype 5, replication-deficient, adenoviral vector (1.2×10⁹ Pfus) containing cDNA encoding the eNOS gene in the hindlimb vasculature for 30 minutes in rats 3 weeks after MI. Five days after infection, overexpression was confirmed by immunohistochemical staining and immunoblotting. Recombinant gene expression was localized to the vascular endothelial cells. ENOS protein level decreased after MI (3.3±0.9 vs. 2.1±0.8 intensity units/μg protein, n=6, P<0.05) and increased two fold (4.3±1.2 intensity units/μg protein, n=5) after gene transfer. Acetylcholine (ACh)-stimulated vasorelaxation in the hindlimb was decreased (P<0.05) by 30% after MI and was restored to normal in MI rats transfected with eNOS. Addition of 100 μM N^G-nitro-L-arginine methyl ester (L-NAME) abolished the difference between sham, MI, and MI transfected rats. The attenuated NO-mediated vasorelaxation in the hindlimb after MI is due to a downregulation of eNOS protein. Overexpression of eNOS restores the ACh-mediated vasorelaxation.