ADP plays a key role in thrombogenesis in rats.

Area of Science:

• Pharmacology
• Hematology
• Thrombosis Research

Background:

• Platelet aggregation plays a crucial role in thrombosis.
• Adenosine diphosphate (ADP), arachidonic acid metabolites, and serotonin are implicated as thrombogenic factors.

Purpose of the Study:

• To evaluate the relative importance of ADP, arachidonic acid metabolites, and serotonin in thrombosis.
• To compare the efficacy of different inhibitors on platelet aggregation and thrombosis models.

Main Methods:

• Oral administration of ADP inhibitors (ticlopidine, PCR 4099), cyclo-oxygenase inhibitors (aspirin, triflusal, indobufen), and a serotonin antagonist (ketanserin) in rats.
• Assessment of platelet aggregation, bleeding time, and thrombus formation in four platelet-dependent thrombosis models.
• Evaluation in fawn-hooded rats with a genetic storage pool deficiency.

Main Results:

• Ticlopidine and PCR 4099 completely inhibited ADP- and collagen-induced platelet aggregation and prolonged bleeding time.
• Cyclo-oxygenase inhibitors only reduced collagen-induced aggregation and did not affect bleeding time.
• Ketanserin and reserpine did not affect platelet aggregation but prolonged bleeding time.
• Ticlopidine and PCR 4099 demonstrated potent antithrombotic effects.
• Aspirin showed weak inhibition of thrombus formation at high doses; triflusal was inactive; indobufen showed slight inhibition.
• Ketanserin and reserpine showed limited antithrombotic effects.
• Fawn-hooded rats exhibited significantly reduced thrombus formation.

Conclusions:

• ADP is a critical mediator of platelet aggregation and thrombosis.
• Inhibitors of ADP-induced platelet aggregation are highly effective antithrombotics.
• Serotonin's role in thrombosis appears less significant than ADP's.
• Cyclo-oxygenase pathway inhibition has a limited role in preventing ADP-dependent thrombosis.