Secondhand Tobacco Smoke Impairs Rabbit Pulmonary Artery Endothelium-Dependent Relaxation

ObjectivesTo determine whether secondhand smoke (SHS) induces pulmonary artery endothelial dysfunction, and whether dietary l-arginine supplementation is preventive.BackgroundSHS causes coronary and peripheral arterial endothelial dysfunction.MethodsThe effects of l-arginine supplementation (2.25% solution) and SHS (10 weeks) on pulmonary vascular reactivity were examined in 32 rabbits fed a normal diet. Endothelium-dependent relaxation of precontracted pulmonary artery segments was studied using acetylcholine and calcium ionophore. Endothelium-independent relaxation was studied using nitroglycerin. Endothelial and serum l-arginine levels were measured by chromatography. In eight SHS-exposed and in eight control rats, pulmonary artery nitric oxide synthase (NOS) activity and arginase activity were studied using the titrated arginine to citrulline conversion assay.ResultsSHS reduced maximal acetylcholine-induced (p = 0.04) and calcium ionophore-induced (p = 0.02) relaxation. l-Arginine increased maximal acetylcholine-induced (p = 0.047) vasodilation. SHS and l-arginine did not influence nitroglycerin-induced relaxation. SHS reduced endothelial l-arginine (p = 0.04) but not serum l-arginine. l-Arginine supplementation increased endothelial (p = 0.007) and serum l-arginine (p < 0.0005). Endothelium-dependent relaxation induced by acetylcholine and calcium ionophore varied directly with endothelial (r = 0.67, r = 0.67) and serum l-arginine (r = 0.43, r = 0.45), respectively. SHS reduced constitutive NOS activity (p = 0.03).ConclusionsSHS reduces pulmonary artery endothelium-dependent relaxation by decreasing NOS activity and possibly by decreasing endothelial arginine content. l-Arginine supplementation increases serum and endothelial l-arginine stores and prevents SHS-induced endothelial dysfunction. l-Arginine may offset the deleterious effect of SHS on pulmonary arteries by substrate loading of the nitric oxide pathway.