Plasminogen interactions with platelets in plasma
B Adelman, A Rizk and E Hanners
Department of Medicine, Medical College of Virginia, Richmond.
In this report we used a fluorescent flow cytometry-based assay to examine
plasminogen binding to platelets in plasma. Our data indicate that
platelets activated in platelet-rich plasma (PRP) by adenosine-5'-
diphosphate (ADP) or thrombin bind plasminogen to their surface. Fab
fragments of the monoclonal antibody LJ-CP8 that are directed against the
fibrinogen binding site on the glycoprotein (GP) IIb-IIIa complex inhibit
both plasminogen and fibrinogen binding to ADP-stimulated platelets as does
5 mmol/L EDTA. Platelet aggregation and plasminogen and fibrinogen binding
are also concurrently inhibited by the Gly-Arg- Asp (RGD) analogue
Gly-Arg-Gly-Asp-Ser (GRGDS) when it is added to PRP before ADP stimulation.
The scrambled peptide analogue SDGRG has no effect. The monoclonal antibody
6D1, directed against the von Willebrand factor binding site on GPIb, has
no effect on plasminogen- platelet binding, nor does antithrombospondin
antibody. epsilon- Aminocaproic acid (EACA), however, inhibits plasminogen
binding to ADP- activated platelets. These data indicate that plasminogen
binds to platelets activated in plasma, that binding occurs on platelet
GPIIb/IIIa, and that binding may be mediated via plasminogen association
with fibrinogen via lysine binding domains. Finally, we found both
plasminogen and fibrinogen on resting platelets in PRP and demonstrated
that they are equally displaced by EDTA, LJ-CP8, and 10E5 (an additional
anti-GPIIb/IIIa monoclonal antibody). Plasminogen is also equally displaced
by EACA. These data suggest that plasminogen is also bound to GPIIb/IIIa on
resting platelets, possibly also via interaction with fibrinogen.
Volume 72,
Issue 5,
pp. 1530-1535,
11/01/1988
Copyright © 1988 by The American Society of Hematology