The relationship of human platelet density to platelet age: platelet
population labeling by monoamine oxidase inhibition
KG Chamberlain, M Tong, E Chiu and DG Penington
University of Melbourne, Department of Medicine, Fitzroy, Victoria,
Australia.
The relationship between platelet density and platelet age appears to vary
between species with relatively few labeling studies in humans reported. In
this study, irreversible monoamine oxidase (MAO) inhibitors were used to
biochemically label the circulating platelet population in 15 humans.
Platelet samples were then isolated during the 15 days after drug
ingestion. The platelets were separated by density on continuous linear
Percoll gradients and the density distributions were divided into five
fractions containing approximately equal numbers of platelets. Baseline MAO
activity was strongly correlated with platelet density. Twenty-four hours
after a single dose of tranylcypromine, platelet MAO activities in the
density subpopulations were reduced to 14% to 17% of the baseline values.
During the first five days after inhibition, the rates of recovery of MAO
activity (percentage per day) were inversely proportional to platelet
density. The recovery rates in the two most dense fractions were initially
slow but increased after five days. Percentage recovery of MAO activity in
the least dense fraction was significantly greater than the percentage
recovery in the most dense fraction on days 2, 3, 5, and 8 (P less than
.01, sign test). These results support the hypothesis that normal human
platelets show a small increase in density with age, but they do not
exclude the additional possibility that human platelet lifespan is
positively correlated with platelet density.
Volume 73,
Issue 5,
pp. 1218-1225,
04/01/1989
Copyright © 1989 by The American Society of Hematology
