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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2006;26:e22.)
© 2006 American Heart Association, Inc.

Letters to the Editor

Physiological Plasma Gas6 Levels Do Not Influence Platelet Aggregation

Sylvain Clauser; Christilla Bachelot-lozat

Institut National de la Santé et de la Recherche, Médicale (INSERM), Faculté des Sciences Pharmaceutiques et Biologique, Université Paris V, Paris, France

Pierre Fontana

Division of Angiology and Haemostasis, Department of Internal Medicine, Faculty of Medicine and University Hospitals of Geneva, Geneva, Switzerland

Pascale Gaussem; Véronique Remones; Martine Aiach; Delphine Borgel

INSERM, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris V, Paris, France

An extract of the first 250 words of the full text is provided, because this article has no abstract.

To the Editor:

Gas6 protein is a vitamin K–dependent protein originally identified as an apoptosis regulator.¹ Gas6 binds to Axl, Mer, and Sky, 3 receptors of the tyrosine kinase subfamily, and was recently implicated in platelet aggregation.² Gas6 knockout mice showed impaired aggregation in response to weak activation with agonists such as 5 µmol/L ADP, 10 µmol/L U46619, and 2 µg/mL collagen. Similarly, loss of any Gas6 receptor impaired the stabilization of platelet aggregates,³ and both Gas6 and Gas6 receptor knockout mice were protected from venous and arterial thrombosis. Gas6 was found to be located in -granules of murine platelets and to be released during platelet activation.^2,4 Data on human platelets are less clear cut. Indeed, preincubation of human platelet-rich plasma (PRP) with an anti-Gas6 antibody inhibited platelet aggregation and secretion responses to both 5 µmol/L ADP and the protease-activated receptor-1 (PAR-1)–activating peptide SFLLRN (20 µmol/L) by >80%.⁵ Using several approaches, Balogh et al found that Gas6 was contained in human blood plasma but not in human platelets, suggesting that in humans, the putative role of Gas6 in platelet aggregation may be played by Gas6 originating from the circulation.⁶

Here, we examined whether human platelet aggregation was influenced by physiological Gas6 plasma levels. Samples from 100 healthy male volunteers 18 to 35 years of age (mean 24.3±3.7 years) were used for platelet aggregation studies and plasma Gas6 assay. Gas6 levels were determined by ELISA as described previously⁷ and were expressed as a percentage of the Gas6 level in a . . . [Full Text of this Article]

This article has been cited by other articles:

				S. Clauser, S. Peyrard, P. Gaussem, M. Crespin, J. Emmerich, M. Aiach, and D. Borgel Development of a Novel Immunoassay for the Assessment of Plasma Gas6 Concentrations and Their Variation with Hormonal Status Clin. Chem., October 1, 2007; 53(10): 1808 - 1813. [Abstract] [Full Text] [PDF]