Platelet ultrastructure and secretion in acute ischemic stroke.

We used transmission electron microscopy to count the organelles (dense bodies, alpha granules, and mitochondria) contained within platelets from 11 acute ischemic stroke patients and 12 healthy controls. We randomly selected for evaluation 25 platelet profiles in ultrathin sections cut from three separate blocks. Compared with those from controls, platelets from stroke patients contained significantly fewer alpha granules (p less than 0.001) and mitochondria (p less than 0.02) and showed a trend toward fewer dense bodies. Supportive of our previous studies, the amount of adenosine triphosphate secreted following stimulation by collagen also tended to be greater in platelets from stroke patients. These observations support the presence of increased platelet secretion associated with acute cerebral infarction and raise the possibility that platelet secretion may be of separate importance to the mechanical occlusion of blood vessels by platelet aggregates in the pathogenesis of cerebral infarction.