NATURAL COURSE OF ENDOTHELIUM-DEPENDENT AND ENDOTHELIUM-INDEPENDENT RESPONSES IN AUTOGENOUS FEMORAL VEINS GRAFTED INTO THE ARTERIAL CIRCULATION OF THE DOG

We examined the natural course of endothelium-dependent and -independe nt responses in reversed autogenous vein grafts during regeneration an d tissue repair processes after vein grafting in dogs. Vein grafts imp lanted in the canine femoral artery were removed, cut into rings, and suspended in organ chambers for isometric tension recording at 3 days and 1, 2, 4, and 6 weeks after implantation. Endothelial cells were de nuded from some rings. Control veins were taken from nonsurgically tre ated femoral veins. Acetylcholine caused endothelium-dependent relaxat ions in the control veins, whereas in the vein grafts there was no evi dence of endothelium-dependent relaxations to acetylcholine 3 days aft er the operation. Acetylcholine caused endothelium-independent contrac tions throughout the study. The endothelium-dependent responses to ADP and calcium ionophore A23187 were constantly maintained. Three days a fter the operation, the amplitude of norepinephrine-induced contractio ns of the vein grafts was impaired, and at 1 week the amplitude was re covered, although it was significantly smaller than the amplitude of c ontractions of the control veins at any postoperative period. Endothel ium-independent relaxations to sodium nitroprusside were maintained th roughout the study. Thus, there was a selective loss of acetylcholine- mediated relaxation in vein grafts in the early postoperative stage, a time when the intima is not thickened. These altered responses in vei n grafts in the early postoperative period may have a role in graft fa ilure.