title: Platelet alpha2-macroglobulin and alpha1-antitrypsin.
abstract: Subcellular membrane and granule fractions derived from human platelets contain immunologically identifiable alpha2-macroglobulin and alpha1-antitrypsin. These platelet-derived inhibitors show a reaction of immunologic identity when compared to alpha2-macroglobulin and alpha1-antitrypsin purified from human plasma. Further, the platelet protease inhibitors possessed a similar subunit polypeptide chain structure to their plasma counterparts as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis. Studies of the binding of radiolabeled trypsin to the various solubilized platelet subcellular fractions suggest that the granule-associated alpha2-macroglobulin and alpha1-antitrypsin, as well as membrane-associated alpha2-macroglobulin were functionally active. Quantitatively, circulating platelets contain relatively small concentrations of these inhibitors as compared to platelet-associated fibrinogen and factor VIIIAGN. Platelet protease inhibitors may modulate the protease-mediated events involved in the formation of hemostatic plugs and thrombi.
mesh_terms: D001792:Blood Platelets / Q000032:analysis*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000032:analysis; D002499:Centrifugation, Density Gradient; D003594:Cytoplasmic Granules / Q000032:analysis; D006801:Humans; D005779:Immunodiffusion; D011233:Precipitin Tests; D013347:Subcellular Fractions / Q000032:analysis; D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins
chemical_list: D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins