Platelet Function in Arteriosclerotic Patients

The clinical significance of platelet function tests in arteriosclerotic patients is not yet defined although the important role of platelets in pathogenesis of arteriosclerosis and its complication have been established. We had encountered a 74-year old male suffered from acute cerebral thrombosis and observed enhancement in his platelet function including release reaction and aggregation immediately after the onset of the disease. To inquire into the mechanism of his interesting results, platelet functions in arteriosclerotic patients are analyzed after exercise test as an analogous state of acute thrombosis and the results were compared to normal healthy controls.Ten healthy males (H) and 21 arteriosclerotic male patients (A) including 13 with ischemic heart disease and 8 with ischemic cerebrovascular disease were exercised on a treadmill using Balke protocol. Blood samples were taken before (C) and immediately after the exercise (E). Platelet functions were studied by measuring maximum intensity of platelet aggregation, platelet sensitivity to ADP-aggregation, plasma β-thromboglobulin (β-TG), plasma platelet factor 4 (PF-4), plasma thromboxane B2 (Tx-B2) and plasma von Will-brand factor (vWF).Maximum intensity of platelet aggregation by collagen 2μg/ml in AC (60.9±5.4%) was significantly enhanced compared to HC (48.1±8.9%). Plasma Tx-B2 in AC (311±17pg/ml) was significantly higher than in HC (254±17). There were, however, no significant changes after the exercise. β-TG levels were significantly elevated after the exercise in both groups; HC: 31.1±3.7, HE: 41.3±5.1, AC: 43.6±6.7, AE: 79.1±11.8ng/ml. But the increment in arteriosclerotic patients was significantly higher comparing to controls. Plasma PF-4 levels were also elevated after the exercise in both groups, but not significant. There was no significant difference between HC and AC in platelet sensitivity to ADP-aggregation and plasma vWF level. But their significant enhancement was seen after the exercise in arteriosclerotic patients. As a summary, in arteriosclerotic patients, the intensity of platelet aggregation and Tx-B2 were elevated before the exercise, and platelet sensitivity to ADP-aggregation, β-TG and vWF were significantly increased after the exercise.These results suggest that enhanced platelet aggregability and increased Tx-B2 were considered to reflect a tendency of platelets to induce aggregation and release reaction, and that the increase in platelet sensitivity to aggregation and platelet release reaction were considered to show a trigger state to induce next thrombotic complication in arteriosclerotic patients.