Summary
To investigate whether the endothelium-platelet interactions may be altered by plasminogen
activation, cultured human umbilical vein endothelial cells (ECs) were treated with
tissue-type plasminogen activator (t-PA) in the presence of plasminogen, and platelet
adhesion to ECs was subsequently measured by using a tapered flow chamber. Our results
demonstrated that platelets adhered more readily to t-PA treated EC monolayer than
to the control monolayer at all shear stress levels tested. This phenomenon was treatment
time-dependent and dose-dependent, and it could be blocked by adding plasmin inhibitors,
such as e-amino caproic acid and aprotinin. Adherent platelets on t-PA treated EC
monolayer underwent more severe shape change than those on the control monolayer.
While the extracellular matrix directly treated with t-PA attracted less platelets
than the control matrix did, platelet adhesion to the matrix that was produced by
t-PA-treated ECs was unaltered. These data suggest that t-PA treatment on ECs compromised
antiplatelet-adhesion capability on their apical surface without altering the reactivity
of their extracellular matrix towards platelets.
