A 15-year-old girl incurs a cut to the sole of her foot after stepping on a piece of broken glass. On examination, a superficial 0.5-cm laceration ceases to bleed within 5 minutes after application of local pressure. Which of the following substances is released by endothelium and is most likely to counteract platelet aggregation near this site of injury?
Glycoprotein IIb/IIIa Platelet-activating factor Prostacyclin Tissue-type plasminogen activator