Overexpression of endothelium nitric oxide synthase reverses the diminished vasorelaxation in the hindlimb vasculature in ischemic heart failure in vivo

After myocardial infarction (MI), nitric oxide (NO)-mediated vasorelaxation is attenuated in both conduit and resistance arteries. To determine if the attenuated vasorelaxation after MI is due to downregulation of eNOS protein, pharmacological immunoblotting, and gene transfer of eNOS were performed in rats 3 weeks after MI. Gene transfer was accomplished using a 'first-generation' serotype 5, replication-deficient, adenoviral vector (1.2 x 10⁹ pfus) containing eNOS cDNA in the hindlimb vasculature for 30 min. Five days after infection, overexpression of eNOS protein was confirmed by immunohistochemical staining and immunoblotting. Recombinant gene expression was localized primarily to the vascular endothelial cells. After MI, eNOS protein level decreased (3.3 ± 0.9 vs 2.1 ± 0.8 intensity units/μg protein, n = 6, P < 0.05): after gene transfer it increased (P < 0.05) two-fold to 4.3 ± 1.2 intensity units/μg protein, n = 5. There were no changes in hemodynamics in MI rats transfected with eNOS. Acetylcholine (ACh)-stimulated vasorelaxation was decreased (P < 0.05)) by 30% after MI and was restored to normal with eNOS transfection. Addition of 100 μM N(G)-nitro-L-arginine methyl ester (L-NAME) abolished the difference between sham, MI, and MI transfected rats. L-arginine (1 mM) restored the ACh-response in MI-transfected rats toward control, but it did not eliminate the difference between MI and sham rats. We conclude that the attenuated endothelial NO-mediated vasorelaxation in the hindlimb after MI is due to a downregulation of eNOS protein and overespression of eNOS transgene restores normal endothelial N0-mediated vasorelaxation.