[Detection of platelet activation].

It is important to detect platelet activation in order to predict prethrombotic states. We investigated the method for detection of in vivo platelet activation. First, we compared the assay of CD62P and Glycocalicin (GC) in plasma with plasma beta-thromboglobulin (beta-TG) measurement. Plasma CD62P and GC assay using enzyme-immunoassay (EIA) was inferior to plasma beta-TG assay in precision. The concentration of CD62P and beta-TG in plasma prepared with anticoagulant mixture was lower than that prepared with Na citrate only. The level of plasma CD62P did not correlate with that of beta-TG and GC and platelet counts, although the level of plasma GC correlated with plasma beta-TG levels positively. These studies suggest that GC may be a useful marker of platelet damage or activation, but CD62P may reflect the activation of endothelial cells rather than platelets. Secondly, we assayed the appearance of activation-dependent granular protein on platelet plasma membrane using flow cytometry. Thrombin stimulated increase in surface expression of CD62P, CD63 and Factor XIII a-chain(XIII-a) on platelet membrane in vitro. The expression of CD63 was more sensitive than that of CD62P. The platelets of patients with chronic hemodialysis showed increased in expression of CD63 and XIII-a compared with control subjects. These data suggest that the surface expression of CD63 and XIII-a on platelets may be useful markers of in vivo platelet activation.