TEMPERATURE-DEPENDENT EFFECTS OF EDTA ON THE MEMBRANE GLYCOPROTEIN-IIB-IIIA COMPLEX AND PLATELET AGGREGABILITY

  • 1 March 1986
    • journal article
    • research article
    • Vol. 67  (3) , 604-611
Abstract
In agreement with previous studies, we observed that incubation of washed human platelets with EDTA at 37.degree. C for short periods caused an irreversible loss of their aggregation response to adenosine diphosphate and markedly diminished their capacity to bind fibrinogen. AP-2 is a monoclonal antibody that reacts with a determinant specific to the glycoprotein (GP) IIb-IIIa complex. We now report that in a direct binding assay, the number of sites for AP-2 on platelets incubated with EDTA at 37.degree. C fell to .apprx. 30% of those present on control platelets. This effect of EDTA was not observed at room temperature. Analysis of the treated platelets by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed normal amounts of GP IIb and GP IIIa. However, studies using crossed immunoelectrophoresis with 125I-AP-2, 125I-Tab (anti-GP IIb), or 126I-AP-3(anti-GP IIIa) in intermediate gels showed that a 37.degree. C, EDTA was inducing an irreversible change in GP IIb-IIIa complexes. A reduction in size and probable dissociation of the GP IIb-IIIa precipitate was accompained by the appearance of precipitates having the characteristics of those given by free GP IIb and free GP IIIa and the location of a major new cathodal precipitate, which bound Tab and AP-3 but not AP-2. Membrane modifications associated with the loss of antigenic determinants on GP IIb-IIIa may explain EDTA-induced loss of platelet aggregability at 37.degree. C.