Platelet Secretion Defect Associated With Impaired Liberation of

We describe four patients with impaired platelet aggrega-tion and 14C-serotonin secretion during stimulation with adenosine diphosphate (ADP), epinephrine. collagen. and platelet-activating factor. The response to arachidonic acid was normal in all patients with regard to aggregation and in three of the four with regard to ‘4C-serotonin secretion. The total platelet adenosine triphosphate (ATP) and ADP content and the ATP to ADP ratio was normal in all patients, thereby excluding storage pool deficiency as the cause of the secretion defect. Studies with 3H-arachidonic acid-labeled platelets revealed that the thrombin-induced liberation of arachidonic acid from membrane-bound phospholipids was impaired in these patients. Further, platelet thromboxane B2 production. measured using a radioimmunoassay. was diminished during stimulation wit