Cigarette smoke impairs endothelium-dependent relaxation in rabbit superficial femoral veins

Background. The use of autogenous vein for arterial reconstruction provides the optimal conduit for limb salvage. Cigarette smoking is a risk factor for vascular disease and may adversely affect graft patency and limb preservation rates of extremities reconstructed with autogenous vein. This study was performed in order to determine the effects of cigarette smoke on venous endothelium-dependent relaxation which is mediated by nitric oxide. Materials and methods. New Zealand white rabbits were exposed to cigarette smoke in a 240-ft³ air-flow chamber for 3 h per day, 5 days per week, for 8 weeks. A control group was treated similarly without infusion of smoke into the chamber. Elevated serum cotinine and carboxyhemoglobin levels comparable to those of chronic smokers were observed in the experimental group. After 8 weeks, the superficial femoral veins were explanted, cut into 3-mm segments, and studied in organ chambers. Results. No difference in contractile response to KCl (80 mM) (control, 0.10 ± 0.06; smoke, 0.17 ± 0.04) or norepinephrine (EC50) (control, 0.78 ± 0.18; smoke, 0.87 ± 0.11) was seen. A significant decrease in relaxation was noted with all doses of acetylcholine (M) (control, 10^-8 50.35 ± 8.37, 3 x 10^-8 - 71.20 ± 9.05, 10^-7 - 88.32 ± 13.72, 3 x 10^-7 - 92.86 ± 13.69; and smoke, 10^-9 - 8.25 ± 1.83*, 3 x 10^-8 - 19.11 ± 5.11*, 10^-7 - 31.84 ± 7.90*, 3 x 10^-7 39.74 ± 8.65*; *P < 0.05). Both control and smoke veins relaxed completely with sodium nitroprusside. Conclusions. Superficial femoral veins, when exposed to cigarette smoke, demonstrated a significant decrease in endothelium-dependent relaxation in response to acetylcholine without smooth muscle injury. This loss of vasomotor tone could be detrimental overtime in veins which have been placed as arterial conduits.