Platelet interaction with damaged rabbit aorta.

We have quantified the accumulation of 51Cr-labeled washed rabbit platelets on the subendothelium of rabbit aortae following injury with a balloon catheter. The amount of radioactivity that became associated with the damaged wall within 10 minutes of the injury did not change appreciably during the following 24 hours, indicating that there was little turnover of platelets on the injured vessel wall. In addition, by injecting 51Cr-labeled platelets into rabbits at different times after injury, it was possible to estimate the reactivity of the exposed surface to newly injected platelets. Scanning electron microscopy showed that a monolayer of platelets initially formed on the injured surface; the number of platelets associated with the surface decreased over the 7-day observation period. The amount of 51Cr associated with the injured vessel wall also diminished during this period. The ability of the damaged surface to attract fresh platelets gradually decreased during the 7 days following injury. Platelet survival in rabbits was not significantly reduced following the removal of the aortic endothelium (balloon catheter injury 66.3 +/- 12.2 hours, sham operated 72.1 +/- 7.2 hours, untreated controls 76.2 +/- 3.8 hours). Thus, in rabbits, it cannot be assumed that platelet survival provides an estimate of endothelial injury in all circumstances.