Thrombin induced platelet adhesion to endothelium is modified by endothelial derived relaxing factor (EDRF)

We investigated the hypothesis that thrombin-induced attachment of platelets to endothelial cells is modulated by EDRF. Thrombin significantly increased binding of radiolabelled platelets to cultured endothelium and to an intact pulmonary vasculature under flow conditions. These increases in binding were potentiated with hemoglobin (HB) and inhibited by superoxide dismutase (SOD) in both systems. We suggest that thrombin, in addition to enhancing platelet adhesion, elicits EDRF release from endothelial cells and that EDRF serves an antithrombotic function in the down regulation of platelet adhesion.