1. Platelets contain separate and distinct α-granule populations
Platelets contain separate and distinct α-granule populations. A, B, and C. Specific pro- and antiangiogenic regulators organize into separate, distinct α granules in resting platelets. Double immunofluorescence microscopy of resting platelets using antibodies against vascular endothelial growth factor (VEGF) (A) and endostatin (B) and an overlay (C). D. Localization of proteins in resting, human platelets using immunoelectron microscopy of ultrathin cryosections. Double immunogold labeling on platelet sections was performed with the use of anti-VEGF antibody and antiendostatin antibodies. Large gold particles representing anti-VEGF staining (15 nm, arrows) are evident on one population of α granules, and small gold particles (5 nm) representing endostatin staining are abundantly present on a different population of α granules (arrowheads). E, F, and G. Pro- and antiangiogenic regulatory proteins are also segregated into separate, distinct α granules in megakaryocyte proplatelets. Megakaryocytes generate platelets by remodeling their cytoplasm into long proplatelet extensions, which serve as assembly lines for platelet production. Distinct α granules are visualized along proplatelets. Shown is a double immunofluorescence microscopy experiment of proplatelets using antibodies against VEGF (E) and endostatin (F), and an overlay (G). (Reproduced with permission from Italiano JE, et al: Angiogenesis is regulated by a novel mechanism: pro- and antiangiogenic proteins are organized into separate platelet alpha granules and differentially released, Blood Feb 1;111(3):1227–1233.)
Source: Platelet Morphology, Biochemistry, and Function, Williams Hematology Hemostasis and Thrombosis
Citation: Kaushansky K, Levi M. Williams Hematology Hemostasis and Thrombosis; 2017 Available at: Accessed: December 22, 2017
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