Summary
A reproducible method is described for quantitating either spontaneous or ADP- induced
platelet aggregation in circulating dog blood after heparinization. An extra- corporeal
shunt containing screen material with openings 53 microns square was placed in the
dog’s arterial circulation. The blood pressure was measured proximal to this filter.
The blood pressure decreased upon opening the shunt to the circulation and increased
when the filter became occluded. The degree and rate of aggregation was determined
by means of measuring these blood pressure changes. Phase and electron microscopy
demonstrated platelet aggregates occluding the filters. Platelet aggregation on the
filter was experimentally accelerated by infusing ADP before the filter. The administration
of ADP in concentrations between 0.625 and 10 μg/ml until occlusion, produced a dose
response relationship between log of ADP concentration and rate of filter occlusion.
Macrodex, a known inhibitor of platelet aggregation was given intravenously and was
found to delay filter occlusion. Similar results were obtained with high intravenous
doses of phenylbutazone. The method was used to compare the drug effects with their
in vitro effects measured photometrically. It would appear that this technique can
be used for demonstrating and quantitating the effects of drugs on the process of
platelet adhesion and aggregation in vivo.
