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 yo ung subjects as well as patients with old cerebral infarction, SPAWB w as determined by the fall in non-aggregated single platelet count by s tirring without adding platelet aggregating agents to whole blood. SPA WB in the aged subjects was significantly higher than that in the youn g volunteers. In patients with old cerebral infarction taking no plate let suppressive agents, SPAWB was also high but was suppressed to the level of that in young subjects by prescription of ticlopidine. Althou gh when aspirin or a mixture of phosphocreatine and creatine phosphoki nase (CP/CPK) was added in vitro to whole blood obtained from the aged subjects, SPAWB was inhibited to 50%, addition of the specific PAF (p latelet activating factor) inhibitor TCV-309 induced only partial inhi bition 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 increas ed thromboxane A(2).