Acetylsalicylic acid inhibits platelet PAI-1 antigen release without affecting circulating PAI-1 antigen in plasma

An important plasminogen activator-inhibitor (PAI-1) is present in plasma and concentrated in alpha-granules of platelets. PAI-1 is released during platelet stimulation in vitro. It is presently unknown to what extent the treatment with acetylsalicylic acid (ASA) inhibits platelet PAI-1 release and if release inhibition has an effect on plasma PAI-1 levels. We therefore investigated by a double-blind placebo-controlled crossover study the effects of oral ASA (500 mg/day for 3 days) on platelet PAI-1 release and on plasma PAI-1 levels of healthy male volunteers. The PAI-1 release from platelets stimulated by arachidonic acid and collagen was significantly reduced by ASA: from average values of 88 and 80% to 14 and 17%, respectively (p less than 0.01). However, plasma PAI-1 levels were not modified by this treatment. We can conclude that platelet PAI-1 release does not play a role in modulating the plasma PAI-1 levels in healthy volunteers.