Summary
Activated platelets are instrumental in restenosis due to their role in thrombus formation.
Aurintricarboxylic acid (ATA) has been reported to prevent platelet activation by
inhibiting von Willebrand factor binding to platelet glycoprotein (GP) Ib. We investigated
the effects of ATA in vitro and in vivo in hamsters. ATA inhibited the in vitro platelet
aggregation induced by ADP, botrocetin and thrombin, but not by collagen. The IC50 values during the ex vivo platelet aggregation by ADP, botrocetin and thrombin were
8.2 ± 1.8 μM, 0.9 ± 0.4 μg/ml and 2.4 ± 0.8 unit/ml, respectively. The platelet retention
time to collagen-coated beads of hamster blood samples was inhibited by ATA (0.1,
0.3 and 1.0 mg/kg per hour) in a dose-dependent manner. Continuous administration
of ATA (0, 0.1, 0.3, 1.0, 3.0 and 10.0 mg/kg per h) via an infusion pump produced
dose-dependent antithrombotic effects: the time to occlude the carotid artery after
vascular injury with a modified catheter was prolonged. Only when infused at doses
of 3.0 and 10.0 mg/kg per hour, bleeding times were significantly prolonged. The continuous
treatment with ATA (1.0 mg/kg per h) using a 2ML1 Alzet infusion pump for 2 weeks,
resulted in a decrease in neointimal area by 22.2 ± 6.8% when measured 2 weeks after
injury induction. DNA synthesis using DDT1MF2 hamster SMCs was decreased by ATA in
a dose-dependent manner. ATA reduced the number of platelets adhering on the injured
area, as detected by electron microscopy. These results indicated that treatment with
ATA inhibited platelet adhesion but also SMC proliferation. These observations may
explain the effect of ATA on neointima formation.