Quantitation of Platelet and Fibrinogen-Fibrin Deposition on Components of Tissue Valves (Ionescu-Shiley) in Calves

With 111In-labeled platelets and 125I-labeled bovine fibrinogen, regional mapping of platelet and fibrinogen deposition on leaflets and sewing rings was obtained. Ten Holstein calves received 25-mm mitral valves (ISLM) and were killed 1, 14, and 30 days after implantation. Twenty-four hours before the calves were killed, 350 to 450 microCi of 111In-labeled platelets and 200 to 250 microCi of 125I-labeled bovine fibrinogen were administered intravenously. The components of the tissue valves, i.e., three leaflets and sewing rings, were separated. Each leaflet was cut into four sections: free edge, central zone, flexion zone, and attachment zone. From the radioactivity in blood, leaflet zones, sewing rings, area of leaflet zones, platelet count, and fibrinogen level in blood, the mean regional density of adherent platelets, fibrinogen-fibrin, and fibrinogen/platelet were calculated. The density of platelets and fibrinogen deposited on the components of the valves decreases with time postimplantation. The number of fibrinogen molecules per platelet is fivefold to 20-fold higher than that of the receptor concentration on platelets on leaflet zones, suggesting the heterogeneity of fibrinogen-fibrin in thrombus and components of the valve.