Which statement accurately describes the role of Prostacyclin in hemostasis?

• A. It promotes platelet aggregation.
• B. It inhibits platelet aggregation.
• C. It converts fibrinogen to fibrin.
• D. It triggers coagulation factor activation.

Answer: (B)

Prostacyclin (PGI2) from the endothelium acts as a powerful anti-platelet signal to keep blood flowing smoothly. It binds to receptors on platelets and raises intracellular cyclic AMP, which dampens the platelets’ ability to become activated, change shape, release granules, and aggregate. This anti-aggregation effect is crucial for preventing clot formation on a healthy vessel lining and helps balance the pro-aggregatory forces in hemostasis. It does not convert fibrinogen to fibrin nor does it initiate coagulation factor activation—that role belongs to the coagulation cascade. Prostacyclin also promotes vasodilation, further reducing platelet adhesion in the vessel.