REDUCTION OF HEPARIN-BINDING TO AND INHIBITION OF PLATELETS BY APROTININ

The direct effect of aprotinin on in vitro platelet function was asses sed by hemostatometry (n = 10). No significant enhancement was demonst rated. However, aprotinin reduced platelet inhibition secondary to hep arin. Hemostatometry demonstrated a significant preservation of in vit ro platelet function (n = 25) (p = 0.04), which was particularly marke d (p = 0.003) in the subgroup (n = 7) demonstrating a severe inhibitio n of platelet function with heparin. Aprotinin significantly reduced t he binding of tritium-labeled heparin to both nonactivated (n = 25) (p = 0.004) and activated platelets (n = 25) (p < 0.0001). We conclude t hat interference with heparin-induced inhibition of platelet function by aprotinin may be one of its hemostatic actions in cardiac surgery. This effect is probably secondary to aprotinin reducing binding of hep arin to platelets.