Simultaneous measurement of epinephrine-induced platelet aggregation in 14 plasma samples

A method is described for the simultaneous measurement of epinephrine-induced platelet aggregation in 14 different plasma samples in 15 min. It is based upon discontinuous registration of platelet aggregation and computer evaluation of the data. The samples are placed in holders mounted over magnetic stirring bars in a 37 degrees C water bath and the extinction is measured by removing the samples one after the other, placing them in a Braun Universal Aggregometer and returning them to their holders in the water bath. The time required to reach 37% of maximal aggregation was chosen as the evaluation criterion. It sufficed for the determination of aggregation sensitivity. This method for the first time permits measurement of a complete titration curve rapidly and under identical conditions and can be used to show the influence of a wide range of aggregation inducers and the concurrent effects of inducers plus various blocking agents. A correlation between aggregation sensitivity and alpha 2-receptor binding capacity in platelets, measured by competitive radioactive binding, was established in samples from 10 healthy volunteers. One group exhibited high aggregation sensitivity coupled with high alpha 2-binding capacity and the other showed low sensitivity with low binding capacity.