Chronic Dietary l -Arginine Prevents Endothelial Dysfunction Secondary to Environmental Tobacco Smoke in Normocholesterolemic Rabbits

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Abstract
Abstract Our goal was to determine whether environmental tobacco smoke causes endothelial dysfunction in the absence of hypercholesterolemia and whether such an effect can be prevented by supplementation with l -arginine. Environmental tobacco smoke exposure is associated with an increase in coronary artery disease events and mortality. We have previously demonstrated that environmental tobacco smoke causes endothelial dysfunction and atherosclerosis in rabbits with diet-induced hypercholesterolemia and atherosclerosis and that chronic dietary l -arginine supplementation prevents this. The effects of l -arginine supplementation (2.25% solution ad libitum) and environmental tobacco smoke (smoking chambers for 10 weeks) were examined with a 2×2 design in 32 rabbits fed a normal diet. Acetylcholine, calcium ionophore A23187, and nitroglycerin-induced vasorelaxation were assessed in aortic rings precontracted with phenylephrine. Endothelial l -arginine levels were measured by chromatography. Chronic l -arginine supplementation increased serum ( P <.001) and endothelial ( P =.003) l -arginine levels. Environmental tobacco smoke reduced endothelium-dependent acetylcholine-induced relaxation, and l -arginine blocked this adverse effect ( P =.04). Environmental tobacco smoke tended to increase phenylephrine-induced contraction ( P =.06). Neither environmental tobacco smoke nor l -arginine influenced A23187-induced relaxation nor endothelium-independent nitroglycerin-induced relaxation. Endothelial dysfunction secondary to environmental tobacco smoke may occur in the absence of diet-induced hypercholesterolemia and atherosclerosis. Chronic dietary supplementation with a nitric oxide donor such as l -arginine offsets the endothelial dysfunction associated with environmental tobacco smoke in normocholesterolemic rabbits, possibly through substrate loading of the nitric oxide pathway.