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Direct demonstration of radiolabeled von willebrand factor binding to platelet glycoprotein Ib and IIb-IIIa in the presence of shear stress (1995)

McCrary, Jeffrey K. ; Nolasco, Leticia H. ; Hellums, J. David ; [et al.]

Springer

Annals of biomedical engineering 23 (1995), S. 787-793

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ISSN: 1573-9686

Keywords: Platelets ; von Willebrand factor ; Glycoproteins Ib and IIb-IIIa ; Shear stress

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: Abstract In this study it is demonstrated for the first time that shear stress induces the binding of exogenous von Willebrand factor (vWF) multimers to platelets. The vWF preparations used were: 125I-vWF purified from human cryoprecipitate (and including all vWF multimers present in normal plasma); and 35S-cysteine-vWF secreted by human umbilical vein endothelial cells (HUVECs) (and containing unusually large vWF forms, as well as all plasma-type vWF multimers). Direct shear-induced binding to washed platelets (300–360×103/μl) of radiolabeled vWF was maximum at 60–120 dynes/cm2 evaluated at 30 sec and was in extent about one-quarter of the binding stimulated by ristocetin after 3 min of incubation. The shear-induced binding of only a small percentage of added radiolabeled vWF was sufficient to initiate aggregation. Radiolabeled vWF attached to both glycoprotein (GP) Ib and GPIIb-IIIa receptors in the shear field, with complete inhibition of binding occurring with simultaneous blockade of both receptors. Binding was potentiated by ADP released from sheared platelets.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00000008

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Second messenger function of phosphatidic acid in platelet activation (1989)

Kroll, Michael H. ; Zavoico, George B. ; Schafer, Andrew I.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 139 (1989), S. 558-564

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ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Phosphatidic acid (PA) is synthesized as the result of the receptor-mediated response of platelets to physiologic agonists. The role of PA in platelet signal transduction, however, is largely unknown. We have examined the responses of platelets to 1-stearoyl-2-arachidonoyl phosphatidic acid (SAPA), the predominant molecular species of human platelet PA. SAPA alone causes platelet aggregation, and pretreatment of platelets with SAPA markedly enhances thrombin-induced aggregation and secretion. Addition of SAPA to intact human platelets causes rapid breakdown of phosphatidylinositol-4,5-bisphosphate (PIP2) and the generation of diacylglycerol and endogenous PA. These reactions are associated with mobilization of intracellular calcium and activation of protein kinase C. SAPA also stimulates the release of endogenous arachidonic acid and its conversion to thromboxane A2. Furthermore, platelet activation by SAPA is blocked by indomethacin, indicating that the actions of SAPA are mediated by cyclooxygenase products. These findings suggest that SAPA may play an important role as an endogenous positive feedback signal to amplify receptor-mediated activation of PIP2-specific phospholipase C in human platelets.

Additional Material: 7 Ill.