Effects of EDTA on the membrane glycoproteins IIb-IIIa complex--analysis using flow cytometry

We developed new monoclonal antibodies (NNKY1-32, NNKY2-6, NNKY2-18) that react with a determinant specific to the GPIIb-IIIa complex, and studied the distribution of GPIIb/IIIa on the platelet surface in vivo and some factors that influence the structure of GPIIb/IIIa using flow cytometry. 1. The surface of large platelets is richer in GPIIb/IIIa than that of small platelets. 2. Incubation of intact platelets with EDTA at 37 degrees C causes progressive dissociation of GPIIb-IIIa complexes, and this influence is marked in small platelets. 3. Addition of Ca2+ or Mg2+ to dissociated GPIIb-IIIa complexes causes reassociation, and additionary ADP after the cation treatment further increases the binding of monoclonal antibodies. 4. Prolonged incubation of intact platelets with EDTA at 37 degrees C induces a peculiar change of structure in the GPIIb/IIIa.