Ca2+ influx mediated through the GPIIb/IIIa complex during platelet activation.
When aequorin-loaded platelets were stimulated with thrombin, the luminescence signal of aequorin showed two peaks. From experiments with 1 mM external Ca2+ or EGTA, both one-half of the first peak and the entire second peak reflected the influx of Ca2+ from the external medium, and the remaining half of the first peak reflected the mobilization of Ca2+ from its storage site. A monoclonal antibody (TM83) that recognizes the glycoprotein IIb/IIIa (GPIIb/IIIa) complex which has binding sites for fibrinogen and the synthetic peptide GRGDSP are known to inhibit fibrinogen binding and platelet aggregation. Both eliminated the second peak of intracellular free calcium ([Ca2+]i). Similar effects were observed during activation by collagen, but not during PMA activation. It was concluded that the GPIIb/IIIa complex was intimately related to a part of the Ca2+ influx during the activation of platelets.
D000331:Aequorin; D000911:Antibodies, Monoclonal / Q000502:physiology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003094:Collagen / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D006801:Humans; D049449:Luminescence; D009842:Oligopeptides / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D009842:Oligopeptides; D010980:Platelet Membrane Glycoproteins; D000331:Aequorin; D004533:Egtazic Acid; D003094:Collagen; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium