While taking an exam on disorders of hemostasis, the students were asked to identify endothelial mediators that inhibit platelet aggregation and also vasodilate vessels. Which of the following would be considered a correct answer? Select all that apply

Question

A) Adenosine diphosphate
B) Prostaglandin I2
C) Thromboxane A2 (TXA2)
D) Nitric oxide
E) Plasminogen

Answer 1

Ans: B, D
Feedback:
If platelets are activated, they are inhibited from adhering to the surrounding uninjured endothelium by endothelial prostacyclin (prostaglandin I2 [PGI2]) and nitric oxide. Both of these mediators are potent vasodilators and inhibitors of platelet aggregation. Endothelial cells also elaborate an enzyme called adenosine diphosphatase that degrades ADP and further inhibits platelet aggregation. The plasma also contains a plasma protein called plasminogen that gets activated and converted to plasmin, an enzyme capable of digesting the fibrin strands of the clot. Release of the vasoconstrictor TXA2 is responsible for much of the vessel spasm. Dense granules mainly contain adenosine diphosphate (ADP), ATP, ionized calcium, serotonin, and histamine, which facilitate platelet adhesion and vasoconstriction at the site of vessel injury.