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Platelet changes after placement of aortic prostheses in dogs. I. Biochemical and functional alterations.

Changes in circulating platelets were observed after placement of woven Dacron aortic prostheses in dogs. Platelets had increased sensitivity to aggregating agents for up to 6 months postoperatively, during which period platelet survival was maximally shortened. Platelet survival gradually lengthened but remained less than preoperative values, even at 18 months. Platelet 5HT, consistently reduced after placement of aortic prostheses, closely paralleled changes in platelet survival. Studies with platelets labeled simultaneously with 14C-5HT and 51Cr suggested in vivo platelet release and reutilization of 5HT. In vitro platelet uptake of 14C-5HT, however, was depressed. Urinary excretion of 5HIAA increased slightly, but not significantly, after placement of aortic prostheses. These findings suggested that platelet interaction with the prosthetic surface led to partial release of platelet storage granule contents. Reutilization of released 5HT occurred but was limited because of impaired platelet uptake or storage of 5HT. Platelet damage was suggested by 51Cr-platelet cross-transfusion experiments. Platelets from normal dogs had normal recovery and reduced survival when cross-transfused into animals with aortic prostheses. When platelets from dogs with aortic prostheses were cross-transfused into normal animals, recovery was strikingly reduced and survival very short. Taken together, these studies suggest that, in dogs, platelet interaction in thrombosis on prosthetic surfaces is, in part, a reversible process, with platelets re-entering the circulation in an altered state.