Evaluation of platelet hyperfunction in aged subjects using spontaneous platelet aggregation in whole blood

To evaluate the changes in platelet function in connection with aging, spontaneous platelet aggregation in whole blood (SPAWB) from healthy aged people was measured and compared to that in the whole blood of young subjects as well as patients with old cerebral infarction. SPAWB was determined by the fall in non-aggregated single platelet count by stirring without adding platelet aggregating agents to whole blood. SPAWB in the aged subjects was significantly higher than that in the young volunteers. In patients with old cerebral infarction taking no platelet suppressive agents, SPAWB was also high but was suppressed to the level of that in young subjects by prescription of ticlopidine. Although when aspirin or a mixture of phosphocreatine and creatine phosphokinase (CP/CPK) was added in vitro to whole blood obtained from the aged subjects, SPAWB was inhibited to 50%, addition of the specific PAF (platelet activating factor) inhibitor TCV-309 induced only partial inhibition of SPAWB. Only CP/CPK showed more than 50% inhibition of SPAWB in the young volunteers. These findings suggest that platelet function in aged subjects is in a hyperaggregable state in vivo due to increased thromboxane A2.