SMOKING IMPAIRS ENDOTHELIUM-DEPENDENT RELAXATION OF SAPHENOUS-VEIN

Samples of proximal saphenous vein were obtained from heavy smokers an d non-smokers: 28 were obtained at varicose vein surgery and eight at infrainguinal bypass surgery. The veins were prepared for histological examination and for mounting in an organ bath to measure changes in i sometric tension. Vein rings from both smokers and non-smokers respond ed equally to sodium nitroprusside, a reagent that acts directly on sm ooth muscle cells, undergoing 90-100 per cent relaxation. The mean(s.e .m.) maximum relaxation in response to bradykinin of rings obtained at varicose vein surgery was 50.0(5.3) per cent in non-smokers compared with only 31.6(2.2) per cent in smokers (P = 0.03). Similarly, in spec imens obtained at bypass surgery the mean(s.e.m.) maximum relaxation i n smokers was only 25.1(6.3) per cent compared with 48.4(4.1) per cent in smokers (P = 0.04). Relaxation in response to the bradykinin stimu lus was abolished in the presence Of L-nitroarginine methyl ester, a s pecific inhibitor of the synthesis of endothelium-derived relaxing fac tor (EDRF). Preincubation of the vein rings with L-arginine, the precu rsor of EDRF, did not increase the vasorelaxation in smokers. The mean (s.e.m.) maximum relaxation in response to the calcium ionophore A2318 7 was 53.5(3.8) per cent in non-smokers compared with only 27.0(4.9) p er cent in smokers (P = 0.01). The results indicate that heavy smokers have impaired release of EDRF in response to both bradykinin and calc ium ionophore. This impairment may increase vasomotor tone, platelet a ggregation and smooth muscle proliferation, thereby resulting in an in creased risk of graft occlusion.