L-arginine availability is not limiting for nitric oxide generation from recombinant endothelial nitric oxide synthase

L-Arginine (L-Arg) may be limiting for inducible nitric oxide synthase (NOS) activity and under certain circumstances, such as increased concentrations of a NOS inhibitor, may also be limiting for endothelial NOS activity. It is unknown if L-Arg is limiting for recombinant eNOS activity in the vascular wall after adenoviral mediated gene transfer. Our aim was to examine, if L-Arg is limiting for recombinant eNOS activity in the normal or atherosclerotic vessel wall. Rings of rabbit aorta from chow or cholesterol fed animals were transduced with adenovirus vector encoding eNOS (AdeNOS) or β-galactosidase (AdβGal). After 24h, transgene expression was confirmed and vasomotor studies were performed in the absence or presence of L-Arg. During maximal contractions to phenylephrine (10^-5 M), L-Arg (3 mM) was added to the organ chamber for 30 min. Subsequently, relaxations to acetylcholine during half-maximal contractions were obtained. In the chow- and cholesterol- fed animals, relaxations were significantly enhanced in the NOS and NOS + L- Arg groups compared to the βGal and βGal +L-Arg groups. There was no difference between NOS and NOS + L-Arg or βGal and βGal + L-Arg rings from chow- or cholesterol-fed animals. While gene transfer of eNOS enhances endothelium-dependent vasorelaxation in the normal and atherosclerotic vessel wall, L-arginine is not limiting for recombinant eNOS activity.