Injury to the aortic endothelium leads rapidly to a deposition of platelets and fibrin at the site of injury. In this study, the responses of individual rabbit plasma proteins, fibrinogen (FBG), prothrombin (PT), antithrombin (AT), heparin cofactor II (HCII), to a deendothelializing injury have been measured. The purified proteins were radiolabeled (125I or 131I). Pairs of radiolabeled proteins were co-injected intravenously into healthy anesthetized rabbits shortly before administration of a deendothelializing (balloon catheter) injury to the thoracic aorta. Each rabbit was exsanguinated at an assigned time (5 - 60 min) after injury, the aorta excised, and the accumulation of each radioactive component/cm2 of aortic intima-media (excluding the platelet layer) was determined. Maximum flux rates of these proteins into the intima-media space (measured as pmol/min/cm2) were calculated immediately after injury relative to radioactivity in blood at exsanguination: FBG, 2.84±0.76 (SD); PT, 0.42 ±0.13; AT, 0.33±0.07; HCII, 0.12±0.03. Thus, approximately 7 molecules of FBG were deposited for each molecule of PT taken up by the deendothelialized aorta surface. In addition, the molar ratio of PT: (AT + HCII) within the intima-media was 0.93, which suggests that these serpins provide tight control of thrombin production at this early stage of injury. These measurements give a vascular wall perspective of an acute hemostatic response in vivo.