VASOACTIVE EFFECTS OF FIBRINOGEN ON SAPHENOUS-VEIN

Normal plasma fibrinogen concentrations are critical to haemostasis. H igher fibrinogen concentrations are associated with increasing risk of atherosclerotic disease(1) and with graft stenosis and occlusion afte r saphenous vein bypass surgery(2,3). Vein graft stenosis is character ized by the localized proliferation of intimal smooth muscle cells, ca using narrowing of the graft with increased risk of thrombotic occlusi on. In rabbit arteries, fibrinopeptide B is reported to have both vaso constrictor and mitogenic properties(4,5). We report here that fibrino peptides had no vasoactive effects on saphenous vein rings; however, f ibrinogen (0-2 mu M) affected an endothelium-dependent relaxation, fol lowed by recontraction at higher concentrations. The fibrinogen-mediat ed relaxation was inhibited by K+-channel blockers and antibodies to I CAM-1. Coupled signalling pathways for the synthesis of vasoactive med iators and mitogens could underlie the association between fibrinogen and the development of vein graft pathology.