Background—Diabetes mellitus is associated with impairment of NO-mediated vascular relaxation. The purpose of this study was to determine whether adenovirus-mediated gene transfer of endothelial NO synthase (eNOS) or Cu/Zn superoxide dismutase (SOD1) improves responsiveness to acetylcholine in alloxan-induced diabetic rabbits.

Methods and Results—After 8 weeks, plasma glucose was greater in diabetic rabbits (418±35 mg/dL) (mean±SEM) than in normal rabbits (105±4 mg/dL). Carotid arteries were removed and cut into ring segments. Arteries were incubated for 2 hours with adenoviral vectors driven by a CMV promoter expressing β-galactosidase (β-gal), eNOS, SOD1, or vehicle. After incubation with virus, arteries were incubated for an additional 24 hours to allow transgene expression. Vascular reactivity was examined by recording isometric tension. After precontraction with phenylephrine, responses to the endothelium-independent vasodilator sodium nitroprusside were similar in diabetic and normal arteries. Endothelium-dependent relaxation to acetylcholine (3×10⁻⁶ mol/L) was significantly less in arteries from diabetic animals (68±5%) than in normal vessels (90±3%). Adenoviral transfection of arteries with eNOS improved relaxation in response to acetylcholine in diabetic (EC₅₀ eNOS=0.64±0.12×10⁻⁷ mol/L versus vehicle =1.70±0.43×10⁻⁷ mol/L) but not normal arteries. Vasorelaxation in response to acetylcholine was inhibited by N^ω-nitro-l-arginine (100 μmol/L) in all groups. Responses to acetylcholine were unchanged after gene transfection of SOD1 or β-gal in arteries from diabetic or normal rabbits.

Conclusions—Adenovirus-mediated gene transfer of eNOS, but not SOD, improves impaired NO-mediated relaxation in vessels from diabetic rabbits.