Platelet interactions with Dacron vascular grafts. A model of acute thrombosis in baboons.

We have developed a model of acute Dacron graft thrombosis in baboons in order to assess platelet alterations secondary to arterial thrombus formation. In this model, thrombus formation was initiated by Dacron vascular grafts inserted as extension segments into chronic arteriovenous Silastic shunts. Following platelet labeling with 111In-oxine, platelet deposition was measured for 1 hour following blood contact under arterial flow conditions using a scintillation camera. Graft platelet activity rapidly increased 40- to 50-fold, plateauing by 1 hour. All grafts produced equivalent reductions in circulating platelet count and blood 111In-platelet radioactivity, demonstrating that the labeled cells were functionally equivalent to the total platelet population. After graft placement, the remaining platelets survived normally. Acute platelet deposition was equivalent on grafts placed 1, 24, 48, and 72 hours following injection of the labeled cells, indicating that a variable delay between platelet labeling and graft imaging was without detectable consequence. Platelet destruction by the graft produced a tenfold increase in plasma levels of platelet factor 4 (PF4) and beta-thromboglobulin (beta TG) but did not modify either the alpha-granule (PF4, beta TG) or dense granule (ADP, ATP) contents of circulating platelets.