Platelet surface glycoprotein changes in patients with cerebral ischemia.

In vitro abnormalities of platelet behaviour have been described in patients with ischemic cerebrovascular disease (ICD) suggesting that changes in platelet receptors and/or platelet a granules may occur in the circulation. We investigated the frequency of such alterations in 95 patients that were studied within a few days after acute stroke. Using specific antibodies to two intrinsic plasma membrane glycoproteins (GPs), the GPIIb-IIIa complex and GPIV, and to thrombospondin (TSP), a a-granular protein that becomes expressed on the platelet surface upon activation, we were able to distinguish two groups of patients: 16 patients presented an increased concentration of TSP on their platelets demonstrating in vivo platelet secretion. These patients could constitute a group with increased risk of thrombosis. In contrast, 20 patients presented a decreased concentration of GPIIb-IIIa and GPIV. This decrease in intrinsic plasma membrane GPs was associated with a decrease in mean platelet volume and may suggest the occurrence of platelet fragmentation in the circulation.