ENDOTHELIUM-DEPENDENT VASODILATION IN THE BRACHIAL-ARTERY IS IMPAIREDIN SMOKERS - EFFECT OF VITAMIN-C

Cigarette smoking has been shown to cause endothelial dysfunction. To examine the effects of vitamin C and cigarette smoking on endothelium- dependent vasodilation, we measured the lumen diameter and flow veloci ty of the brachial arteries at rest, during reactive hyperemia followi ng transient arterial occlusion, and after sublingual nitroglycerin (0 .3 mg) in smokers (n = 20) and nonsmokers (n = 20) with high-resolutio n ultrasound after infusion of saline or saline plus vitamin C (10 mg/ min for 20 min). We also performed the same study in smokers (n = 15) before and 10 min after cigarette smoking. In addition, we measured th e serum levels of vitamin C and the plasma levels of thiobarbituric ac id-reactive substances (TEARS) as an index of lipid peroxidation. The smokers had lower vitamin C levels, higher TEARS levels, and showed im pairment of from-dependent vasodilation (5.3 +/- 1.9 vs. 9.2 +/- 1.5%, P < 0.0001) compared with nonsmokers. Vitamin C administration improv ed the impairment of flow-dependent vasodilation (5.3 +/- 1.9 to 9.0 /- 3.2%, P < 0.001) and decreased TEARS in smokers but not in nonsmoke rs. Furthermore, cigarette smoking acutely worsened the impairment of flow-dependent vasodilation (5.4 +/- 1.8 to 1.5 +/- 1.3%, P < 0.01) an d increased TEARS. We conclude that 1) endothelium-dependent vasodilat ion in the brachial arteries is impaired in smokers and this impairmen t is improved by vitamin C administration in association with a decrea se in TEARS and 2) cigarette smoking produces acute impairment of endo thelium-dependent vasodilation in smokers in association with an incre ase in TEARS.