Abstract
Aspirin is known as an agent which inhibits platelet malondialdehyde (MDA) production and its aggregation by blocking cyclooxygenase.
Recently, Stuart et al described a new method for measuring platelet survival by using this principle. It is very useful because its technique is very simple and nonradioisotopic, however there are some problems must be clarified further on it.
In this paper, observation of platelet kinetics by a single low-dose aspirin administrated orally, or intravenously as a pulse labeling in normal volunteers were investigated.
The mean platelet survival time is calculated with linear recovery of daily MDA formation using a computer programme.
In normal subjects administrated single oral dose of 500mg or 1.0g aspirin, platelet survival curve revealed a lag phase for the first two days, followed by linear recovery, and the mean platelet survival time was 9.7±1.4 (M±SD) days. It has been suggested that high-dose aspirin inactivates the cyclooxygenase not only in peripheral platelets, but megakaryocytes in bone marrow.
The mean platelet survival time after oral administration of low-dose aspirin (63mg, 125mg) was 8.9±1.4 days and that after intravenous injection (50mg, 100mg) was 8.7±0.3 days respectively, which are shorter than that after oral high-dose aspirin.
MDA production was inhibited completely and immediately after the intravenous injection of aspirin (50mg or 100mg). Platelet survival curve showed almost linear without a lag phase during the first two days in this case.
It is concluded that platelet survival time should be measured by using low-dose intravenous pulse labeling technique.
