AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 6 776-R784, Copyright © 1983 by American Physiological Society
Analysis of platelet aggregation using particle collision theory
T. M. Davis and E. Bown
The aggregometer monitors changes in light transmission through stirred
suspensions of aggregation platelets. Arbitrary measurements from
aggregometer recorder tracings have been used to investigate platelet
aggregation without regard to mechanisms involved. To determine the
applicability of particle collision theory to assessment of in vitro
platelet sensitivity to proaggregating agents, platelet-rich plasma (PRP)
from five volunteers was used to obtain recorder tracings after addition of
ADP in five doses (0.4-4.0 mumol/l PRP) to aliquots of PRP stirred and
incubated in an aggregometer. Using the equation describing light
transmission through particulate suspensions, particle collision theory,
and s (the probability of particle union after collision), a subject- and
dose-independent relationship between aggregation rate (dn/dt) and particle
number (n) at the recorder tracing inflection point was found (dn/dt = -k X
s X n1.56, where k is a constant dependent on particle size and speed and
on the proportion of unreactive particles). Determinations of mean particle
size at the tracing inflection point indicated that k was also dose
independent. Dose-response curves of ADP added vs. s could therefore be
constructed. This methodology provides conveniently obtainable quantitative
information concerning in vitro platelet "stickiness."
