The
gray platelet syndrome is a rare inherited platelet disorder characterized by the absence of alp ha-granules as observed by electron microscopy. Analysis of the
glycoprotein composition of the platelets of 2 such patients by SDS-
polyacrylamide gel electrophoresis (SDS-PAGE) revealed decreased or absent staining for
carbohydrate of several high molecular weight
glycoproteins. The major
periodic acid Schiff (PAS) staining
membrane glycoproteins were normally detected and were normally labeled with 125I during
lactoperoxidase-catalyzed iodination. Analysis of the
protein composition of gray platelets by single or two-dimensional SDS-PAGE followed by
Coomassie blue staining revealed an apparent absence of GP Ig (
thrombospondin), markedly reduced platelet
fibrinogen and
albumin concentrations, and severely reduced levels of 2 low molecular weight
polypeptides exhibiting identical rates of migration on SDS-PAGE as
platelet factor 4 and
beta-thromboglobulin. SDS-PAGE profiles similar to those of the gray platelets were observed with normal human platelets that had undergone the release reaction induced by
thrombin. Analysis of gray platelet
proteins by crossed immunoelectrophoresis using a rabbit anti-human platelet antibody preparation and rocket immunoelectrophoresis using monospecific
antisera confirmed the above findings and showed additional severe deficiencies of
factor VIIIR:Ag and cold-insoluble
globulin. In contrast,
factor XIII (subunit A), a cytoplasmic
protein, was normally detected. Our studies provide further evidence that circulating gray platelets specifically lack, or have markedly decreased concentrations of, the alpha-granule
proteins.