Quantitation of prothrombin.

(A) A representative immunoblot of prothrombin. Consecutive 30-second bleeding-time blood samples were separated on a 5% to 15% linear gradient SDS-PAGE gel under reducing conditions. Prothrombin was probed with a polyclonal antibody (Figure 2). Wells A—blood samples taken before aspirin (ASA) ingestion (75 mg/d for 7 days); wells B—samples after aspirin therapy. (B) Quantitative analysis of removal of prothrombin from supernatants of bleeding-time blood. Levels of prothrombin, determined by densitometry and comparison with standards, are presented as a function of time (seconds). Total amounts of prothrombin before (open triangles) and after aspirin treatment (closed triangles). Concentrations of prothrombin before (open circles) and after aspirin treatment (closed circles). (C) Prothrombinase formation calculated in each 30-second bleeding-time blood sample, as described in “Materials and methods.” Total amounts of prothrombinase before (open circles) and after aspirin treatment (closed circles). Concentrations of prothrombinase before (open squares) and after aspirin treatment (closed squares). Values are plotted as means ± SEM.