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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Rao, L. V. Articles by Rapaport, S. I. Search for Related Content PubMed PubMed Citation Articles by Rao, L. V. Articles by Rapaport, S. I. Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  The effect of platelets upon factor Xa-catalyzed activation of factor VII in vitro LV Rao and SI Rapaport Department of Medicine, University of California, San Diego, La Jolla. The authors have investigated the ability of platelets to enhance factor Xa-catalyzed activation of factor VII. Unstimulated platelets were without effect, whereas freeze/thawed platelets substantially enhanced activation. Antifactor V antibodies did not diminish the enhancement. Platelets activated by thrombin, collagen, or calcium ionophore A23187 also enhanced factor Xa-catalyzed activation of factor VII. In contrast to their lack of effect upon freeze/thawed platelets, antifactor V antibodies abolished augmented factor VII activation induced by activated platelets. Adding exogenous factor Va to unstimulated platelets failed to enhance factor Xa-catalyzed activation of factor VII, nor did adding exogenous factor Va to activated platelets augment activation beyond that observed with activated platelets alone. These observations can be interpreted as follows: (1) factor Va does not function as a cofactor for factor Xa-catalyzed activation of factor VII; (2) anionic phospholipids are a known cofactor for factor Xa-catalyzed activation of factor VII, and freeze/thawed platelets probably enhance activation by making anionic phospholipids on disrupted platelet membranes available to function as a cofactor; (3) the presumed binding of factor Xa to exogenous factor Va on unstimulated platelets is insufficient in itself to augment factor Xa-catalyzed activation of factor VII; (4) activated platelets augment factor Xa-catalyzed factor VII activation because activation allows both factor Xa to bind to released platelet factor V(a) and makes available a surface membrane component, probably anionic phospholipids, with which the bound factor Xa interacts. Volume 72, Issue 2, pp. 396-401, 08/01/1988 Copyright © 1988 by The American Society of Hematology CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: S. Butenas, C. van `t Veer, and K. G. Mann Evaluation of the Initiation Phase of Blood Coagulation Using Ultrasensitive Assays for Serine Proteases J. Biol. Chem., August 22, 1997; 272(34): 21527 - 21533. [Abstract] [Full Text] [PDF]

	Copyright © 1988 by American Society of Hematology         Online ISSN: 1528-0020