MEASUREMENT OF HUMAN PLATELET MICROAGGREGATES BY A NEW METHOD - ULTRASONIC INTERFEROMETRY

We have adapted the ultrasonic interferometry technique (Echo-Cell), w hich was initially designed to study red blood cell aggregation and ag glutination, to the detection of human platelet microaggregates. The e xperimental parameter chosen was the slope of the signal over the firs t 5 minutes of sedimentation. We compared our new method with the conv entional aggregometry for the measurement of aggregates after thrombin -, collagen-, and epinephrine-induced platelet activation. Under these conditions we demonstrated the particular sensibility of the present method in detecting small platelet aggregates induced in the first pha se of aggregation and formed by low concentrations of agonists. Furthe rmore, as an illustration of this method, we showed an inhibition of t he formation of thrombin-induced platelet aggregates in a concentratio n-dependent manner by the well-known antagonist arginine-glycine-aspar tic acid-serine with a median inhibitory concentration of 0.4 mu mol/L , which is 30 times lower than the median inhibitory concentration fou nd by aggregometry.