Enhancing effect by heparin on shear-induced platelet aggregation.

We have recently developed a new device for continuously measuring SIPA. Using the device, we have investigated the effects of heparin on SIPA. Heparin itself enhanced SIPA in the absence of agonists in a dose-dependent manner, whereas heparinoids had minimal effects on SIPA. LMW heparin had less enhancing effect on SIPA than unfractionated heparin. Effects of heparin were also investigated using PRP from patients with congenital bleeding disorders, including Bernard-Soulier syndrome, type III von Willebrand's disease, afibrinogenemia and Glanzmann's thrombasthenia. Heparin's effects were observed only when PRP from patients with Bernard-Soulier syndrome and type III von Willebrand's disease was exposed to low shear stress and when PRP from a patient with afibrinogenemia was exposed to high shear stress. These results gave us insights into heparin's effects on platelet aggregation.