Non-identity of the α-Granules of Human Blood Platelets with Typical Lysosomes

Siegel, Alan J.; Lüscher, E. F.

doi:10.1038/215745a0

Cited by 57 publications

(23 citation statements)

References 12 publications

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“…Further separation of the granule fraction by isopycnic centrifugation on a sucrose gradient revealed factor V and LA-PF4 to be maximal in a denser fraction of the gradient than the acid hydrolases. The acid hydrolases are not located in the a granules (23,24), whereas the heparin-neutralizing proteins (25,26), fibrinogen (27), fibronectin (28), von Willebrand factor (29), and platelet-deprived growth factor (26) are. Our data suggest that factor V is also an a granule constituent.…”

Section: Discussionmentioning

confidence: 99%

Subcellular localization and secretion of factor V from human platelets.

Chesney¹,

Pifer²,

Colman³

1981

Proc. Natl. Acad. Sci. U.S.A.

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ABSTRACT' Factor V, a plasma protein cofactor necessary for optimal conversion of prothrombin to thrombin, is also present in considerable concentration in blood platelets (9.9 units per 109 platelets). Subcellular fractionation by. two methods has localized factor V in the a granules of-unstimulated platelets. ADP and epinephrine cause release of4.6% and 6.4%, respectively, ofthe total factor V, a process completely inhibited by cyclooxygenase alkylation by aspirin. In contrast, collagen causes release of 25% of platelet factor V, a process only partially suppressed by aspirin. Secretion of factor V depends on the availability of metabolic energy, because antimycin A,. an inhibitor of aerobic metabolism, and 2-deoxyglucose, an inhibitor of anaerobic glycolysis, together almost totally inhibited the secretion of factor V induced by collagen. The data establish that factor V is not normally available on unstimulated platelets but can be secreted from a granules upon stimulation with physiological agents such as ADP, epinephrine, and collagen. Because factor V is known to serve as a receptor for factor Xa, the exposure of factor V on platelets consequent to release would accelerate the process of blood coagulation.One year after the discovery of factor V in plasma, Ware et al.(1) recognized that platelets also contain an accelerator of prothrombin conversion. Though this coagulant activity was more stable to heat inactivation and storage than was plasma factor V, it was generally assumed to be the plasma factor adsorbed to the platelet surface (2, 3). In 1975, Breederveld et aL (4), using gel filtration to isolate platelets from plasma, found minimal activity of factor V associated with platelets but were able to increase the V activity by freeze-thawing. 0sterud et aL (5) confirmed this observation and showed that platelets contain an activated form offactor V as well as a platelet activator ofplasma factor V. Kane et aL (6) have presented convincing evidence that factor Xa binds to the platelet membrane at a binding site that is identical to or requires the presence of factor V.Despite these important observations, several questions remain in evaluating the influence of platelet factor V on the hemostatic and possible thrombotic processes. What is the sub, cellular localization offactor V? Are prostaglandin synthesis and metabolic energy required for its release? Do collagen, ADP, and epinephrine release factor V as thrombin does? This study attempts to answer these questions. MATERIALS AND METHODSBovine serum albumin (fraction V), ADP, epinephrine, and bovine fibrinogen (fraction 1, type IV, 93% clottable) were supplied by Sigma. Human fibrinogen (grade L, 95%

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Section: Discussionmentioning

confidence: 99%

Subcellular localization and secretion of factor V from human platelets.

Chesney¹,

Pifer²,

Colman³

1981

Proc. Natl. Acad. Sci. U.S.A.

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“…The chemical composition of the a-granule is less well defined than that of the "serotonin" granule, yet it is the former granule which is purported to be the platelet lysosome (4-7, 9, 10). Although this opinion is widely accepted, it has been questioned by Siegel and Luscher (13) and more recently by Broekman et al (14). In both these studies, only low levels of acid hydrolase activities could be demonstrated in a-granule fractions, whereas fractions with high activities were morphologically heterogeneous and therefore difficult to interpret.…”

Section: Introductionmentioning

confidence: 98%

Cytochemical localization of lysosomal enzymes in rat megakaryocytes and platelets.

Bentfeld¹,

Bainton²

1975

J. Clin. Invest.

109

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A B S T R A C T Platelets secrete lysosomal enzymes during the "platelet release reaction" early in clot formation. This study was undertaken to identify primary lysosomes of platelets and to determine their origin in megakaryocytes. Using electron microscopy and cytochemistry, we localized two lysosomal enzymes, arylsulfatase and acid phosphatase, in megakaryocytes and platelets of normal and thrombocytopenic rats. In platelets and mature megakaryocytes, reaction product for both enzymes is confined to vesicles measuring 175-250 nm. These vesicles, which are primary lysosomes, first appear in the earliest recognizable megakaryocytes and increase in number during cellular maturation. In immature and maturing megakaryocytes, arylsulfatase and acid phosphatase can also be demonstrated in an organelle similar to GERL (Golgi-endoplasmic reticulumlysosome), i.e., a single smooth-surfaced cisterna with associated vesicles near the stacked Golgi cisternae. Scant reaction product for acid phosphatase is also sometimes seen in Golgi cisternae and endoplasmic reticulum. No reaction product was found in a-granules at any stage of megakaryocyte maturation, nor in a-or serotonin granules of platelets. Thus, our findings indicate that the primary lysosomes of megakaryocytes and platelets are small vesicles derived from GERL early in megakaryocyte differentiation. They can be identified only after cytochemical staining and are distinct from both a-and serotonin granules.

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“…Adenylate kinase is released from human platelets during aggregation by ADP (Haslam & Mills, 1967). We have measured the release from platelets during aggregation of fi-glucuronidase, a lysosomal enzyme (Gianetto & De Duve, 1955); acid phosphatase, which has been found in both lysosomal and non-lysosomal granules in platelets (Siegel & Luscher, 1967); and adenylate kinase. The latter, a low molecular weight enzyme present in soluble form in cytoplasm, was chosen as a control for platelet 723 724 D. C. B.…”

Section: Introductionmentioning

confidence: 99%

The release of nucleotides, 5‐hydroxytryptamine and enzymes from human blood platelets during aggregation

Mills¹,

Robb²,

Roberts³

1968

The Journal of Physiology

310

112

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SUMMARY1. Adenosine diphosphate (ADP) and adrenaline caused the aggregation of human platelets suspended in plasma containing citrate anticoagulant and stirred at 370 C. The aggregation occurred in two phases and the second phase was associated with the appearance in the plasma of up to 30 % of the ATP and 55 % of the ADP present in the platelets. The concentration of ADP appearing in the plasma was up to 7 times the concentration added.2. Radioactivity was released by ADP and by adrenaline from platelets labelled with radioactive 5-hydroxytryptamine; this release was closely correlated with the second phase of aggregation and with the release of nucleotides.3. Acid phosphatase, ,-glucuronidase and adenylate kinase were released to a small extent during second phase aggregation by ADP or adrenaline; thrombin and collagen particles caused significantly greater release of fi-glucuronidase than of either acid phosphatase or of adenylate kinase.4. Morphological changes indicating degranulation of the platelets were observed during the second phase of aggregation produced by adrenaline and by ADP.5. The second phase of aggregation, degranulation of platelets, and the release of nucleotides, of labelled 5-hydroxytryptamine and of enzymes, were all inhibited by concentrations of amitriptyline which did not inhibit aggregation.

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Non-identity of the α-Granules of Human Blood Platelets with Typical Lysosomes

Cited by 57 publications

References 12 publications

Subcellular localization and secretion of factor V from human platelets.

Subcellular localization and secretion of factor V from human platelets.

Cytochemical localization of lysosomal enzymes in rat megakaryocytes and platelets.

The release of nucleotides, 5‐hydroxytryptamine and enzymes from human blood platelets during aggregation

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