Changes Associated with Platelet Aging^[*]

Summary

Cohorts of “young” and “old” platelets were prepared and compared with each other, and with total platelet populations. It was found that approximately 22% of the platelet mass, including phospholipid, cholesterol and protein was lost as the platelets aged in the circulation. No one phospholipid fraction was specifically altered. With aging there was significant reduction in the ability of platelets to respond to aggregating stimuli and to release Pf3. Pf4 activity seemed to be fully preserved and there was no detectable change in specific gravity. Ultrastructural changes seemed to be limited to a decrease in the number of glycogen granules.

It is recognised that the observed changes may be a passive consequence of platelet aging. However, it is speculated that loss of platelet substance may in someway be related to a functional role of platelets - perhaps the maintenance of endothelial integrity.

It is also postulated, on the basis of the reported findings, that radioisotopic labels such as DFP which give an exponential platelet survival curve bind to a platelet constituent which is lost during the aging process.

^* This work was presented in part at the XII Congress of the International Society of Haematology in September 1968 in New York (Abstract page 199) and was published in abstract form in Clin. Res. 17: 325 (1969)

^** Present address: Queen’s University Department of Medicine Kingston, Ontario, Canada.

^*** Present address : Milwaukee Blood Center, 763North 18 th Street, Milwaukee, Wisconsin 53233.

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