Cerebrovascular injuries induced by activation of platelets in vivo

Abstract

Intravascular platelet aggregation induced by ADP injection into the carotid artery of rabbits caused ipsilateral cerebrovascular injuries. We have observed the details of these in vivo vascular changes under the electron microscope. Intracytoplasmic vacuole (1.0-2.0 µm in diameter) formation and partial deendothelialization followed by platelet thrombus formation were characteristic changes in the middle cerebral artery. These vacuoles did not contain horseradish peroxidase (HRP) which was used as a marker of vascular permeability change. Compared with these phenomenon, increased vesicular (0.05-0.2 µm in diameter) transport was prominent, and vacuole formation was rarely seen in small vessels, namely, capillaries and arterioles in the cortex. Endothelial cell damage seemed to be more prominent in large arteries, but only the smaller vessels show marked extravasation of HRP-reaction product and perivascular edema. Blood levels of TXB2 and 6-keto PGF1a were significantly increased 3 min after the ADP injection and returned to pre-injection levels at 60 min after. These results suggest that vasoactive substances resulting from platelet activation may play an important role in producing cerebrovascular injuries caused by platelet aggregation induced with ADP. © 1985 American Heart Association, Inc.