Release Reaction in Washed Platelet Suspensions Induced by Kaolin and Other Particles

A method is described for testing the release of ADP in a platelet suspension induced by kaolin, latex, other particles and distilled water. A refined technique was developed to determine ADP quantitatively by its ability to aggregate platelets. Total adenine nucleotide release was also determined spectrophotometrically. Both methods have advantages and disadvantages. In a platelet suspension the release induced by kaolin occurred in the absence of cofactors and even in the presence of EDTA. Maximal release occurred at 37° C. In the absence of other inducers, calcium alone did not produce release, but it potentiated the release by other inducers, which was most conspicious at low temperatures. The release reaction of this type was not mediated by thrombin and was not inhibited by acetylsalicylic acid. Adhesion of platelets to the particles evidently preceded the release. Patients were investigated and a normal or increased release was found in Glanzmann's thrombasthenia and von Willebrand's disease. A patient with prolonged bleeding time showed and isolated decrease in the total content of ADP.