REGRESSION OF INTIMAL HYPERPLASIA WITH RESTORATION OF ENDOTHELIUM-DEPENDENT RELAXING FACTOR-MEDIATED RELAXATION IN EXPERIMENTAL VEIN GRAFTS

Background. The reversibility of the morphologic and functional altera tions that occur in veins transplanted into the arterial circulation w as examined in this study. Methods. Common carotid vein bypass grafts (VG) were performed in 20 male New Zealand White rabbits. Ten VG and j ugular veins (CV) were harvested after 14 days, and ten VG were reimpl anted as venovenous bypass grafts (REV) and harvested after an additio nal 14 days. Vessels were taken for structural or isometric tension st udies to norepinephrine, serotonin, and bradykinin and to acetylcholin e and sodium nitroprusside after precontraction. Results. There was a decrease in the thickness of the intima (p = 0.02) and the media (p = 0.002) in REV compared with VG. In REV, sensitivity to norepinephrine decreased (p = 0.0007) with a reduced maximal tension to norepinephrin e (p = 0.02) and to serotonin (p = 0.0001). Bradykinin sensitivity inc reased in REV (p = 0.003 vs VG) and was greater than in CV. Only the p recontracted CV and REV relaxed to acetylcholine. All tissues relaxed to sodium nitroprusside. Conclusions. This study suggests that intimal hyperplasia can be reversed with restoration of endothelium-dependent relaxing factor-mediated relaxation but that only a partial regressio n of the contractile abnormalities can be achieved.