Platelet size and age determine platelet function independently
CB Thompson, JA Jakubowski, PG Quinn, D Deykin and CR Valeri
This study was undertaken to examine the interaction of platelet size and
age in determining in vitro platelet function. Baboon megakaryocytes were
labeled in vivo by the injection of 75Se- methionine. Blood was collected
when the label was predominantly associated with younger platelets (day 2)
and with older platelets (day 9). Size-dependent platelet subpopulations
were prepared on both days by counterflow centrifugation. The reactivity of
each platelet subpopulation was determined on both days by measuring
thrombin-induced aggregation. Platelets were fixed after partial
aggregation had occurred by the addition of EDTA/formalin. After removal of
the aggregated platelets by differential centrifugation, the supernatant
medium was assayed for remaining platelets and 75Se radioactivity.
Comparing day 2 and day 9, no significant difference was seen in the rate
of aggregation of a given subpopulation. However, aggregation was more
rapid in the larger platelet fractions than in the smaller ones on both
days. A greater percentage of the 75Se radioactivity appeared in the
platelet aggregates on day 2 than on day 9. This effect was independent of
platelet size, as it occurred to a similar extent in the unfractionated
platelets and in each of the size-dependent platelet subpopulations. The
data indicate that young platelets are more active than older platelets.
This study demonstrates that size and age are both determinants of platelet
function, but by independent mechanisms.
Volume 63,
Issue 6,
pp. 1372-1375,
06/01/1984
Copyright © 1984 by The American Society of Hematology
