Ascorbic acid prevents cigarette smoke injury to endothelium-dependent arterial relaxation

Background. Arterial endothelium-dependent acetylcholine relaxation is impa ired by smoking, and this injury may be mediated by oxygen free radicals, T he purpose of this study was to examine the effect of ascorbic acid (AA) tr eatment on this injury, Materials and methods. New Zealand White rabbits (n = 6, each group) were p laced in a 240-ft(3) airflow chamber for 3 h per day, 5 days per week over an 8-week period. Animals were divided into four groups and fed rabbit chow and water or rabbit chow and AA (250 ml/kg)-supplemented water. The contro l-smoke rabbit group and the ascorbic acid-smoke rabbit group were exposed to mainstream cigarette smoke from a robotic smoke generator for the 3-h pe riod, while the control-no smoke rabbit group and ascorbic acid-no smoke ra bbit group were similarly placed in the chamber without smoke. At the end o f 8 weeks, rabbits were sacrificed and segments of their superficial femora l arteries were suspended from tension transducers and the maximal contract ion was determined, The remaining rings were contracted to 50% of the maxim um and relaxation was determined by adding acetylcholine. Groups were compa red using one-way ANOVA. Results. Rings from control-smoke (5.13 +/- 0.21 g) and AA-smoke rabbits (6 .24 +/- 0.46 g) exhibited increased mean contraction to KCI (P < 0.05) comp ared to control-no smoke rabbits (3.86 +/- 0.40 g), Acetylcholine-dependent relaxation was significantly reduced in the rings from the control-smoke r abbits compared to control-no smoke rabbits (acetylcholine, 5 x 10(-7) M: 2 4.7 +/- 2.7% versus 55.3 +/- 8.0%; acetylcholine, 7 x 10(-7) M: 27.5 +/- 2. 3% versus 56.3 +/- 9.2%). The AA-smoke group (acetylcholine, 5 x 10(-7) M: 61.8 +/- 12.4%; 7 x 10(-7) M: 67.9 +/- 11.4%) had significantly increased r elaxation compared to the control-smoke group (P < 0.05), There was no stat istical difference in the mean percentage ring relaxation between the contr ol-no smoke, AA-no smoke, and AA-smoke groups, Conclusions. Ascorbic acid protected the artery from cigarette smoke-induce d endothelial injury. (C) 1999 Academic Press.