This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map 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 Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by De Candia, E. Articles by Landolfi, R. Search for Related Content PubMed PubMed Citation Articles by De Candia, E. Articles by Landolfi, R. Related Collections Anticoagulant mechanisms Platelets

(Circulation. 1999;99:3308-3314.)
© 1999 American Heart Association, Inc.

Basic Science Reports

Thrombin-Induced Platelet Activation Is Inhibited by High- and Low-Molecular-Weight Heparin

E. De Candia, MD; R. De Cristofaro, MD; R. Landolfi, MD

From the Istituto di Semeiotica Medica, Università Cattolica del Sacro Cuore, Rome, Italy.

Correspondence to Dr Raffaele Landolfi, Istituto di Semeiotica Medica, Università Cattolica del Sacro Cuore, Largo F. Vito, 1, 00168 Roma, Italy.

Background—Thrombin binds to platelet glycoprotein Ib (Gp Ib), and this interaction contributes to platelet activation. Thrombin ligation to Gp Ib was recently shown to be inhibited by heparin, thus raising the hypothesis, investigated in this article, that heparin might inhibit thrombin-induced platelet activation.

Methods and Results—Aggregation of gel-filtered platelets by 1 nmol/L thrombin was reduced by both high-molecular-weight (MW) (14 500-Da) and low-MW (4500-Da) heparin, with IC₅₀ values of 1.65±0.26 and 5.13±0.8 µmol/L, respectively. Homogeneous-MW fractions (16 000- to 13 000-Da range) were used to evaluate the heparin effect on intracytoplasmic calcium release by thrombin. Calcium mobilization by 1 nmol/L thrombin was reduced as a function of heparin concentration, and the inhibitory effect was correlated to the MW of heparin fractions (IC₅₀ values were 1.9±0.39, 6.07±0.83, and 14.8±0.43 µmol/L for 16 000-, 9000-, and 3000-Da heparin, respectively). Platelet aggregation and calcium mobilization by ADP and by the thrombin receptor–activating peptide were not affected by heparin. The activation of Gp Ib–depleted platelets by -thrombin was not inhibited by heparin. Moreover, platelet stimulation by heparin binding site phosphopyridoxylated thrombin, which has a severe impairment of Gp Ib ligation, was not affected by heparin. Finally, heparin did not interfere with the hydrolysis by thrombin of the protease-activated receptor 1.

Conclusions—These results demonstrated that heparin, by inhibiting the thrombin–Gp Ib interaction, is able to interfere with thrombin-induced platelet activation. The extent of the inhibitory effect is directly related to the MW of heparin fractions.

Key Words: platelets • receptors • glycoproteins • heparin

This article has been cited by other articles:

				A. Cumashi, N. A. Ushakova, M. E. Preobrazhenskaya, A. D'Incecco, A. Piccoli, L. Totani, N. Tinari, G. E. Morozevich, A. E. Berman, M. I. Bilan, et al. A comparative study of the anti-inflammatory, anticoagulant, antiangiogenic, and antiadhesive activities of nine different fucoidans from brown seaweeds Glycobiology, May 1, 2007; 17(5): 541 - 552. [Abstract] [Full Text] [PDF]

				J R S Day, I S Malik, A Weerasinghe, M Poullis, I Nadra, D O Haskard, K M Taylor, and R C Landis Distinct yet complementary mechanisms of heparin and glycoprotein IIb/IIIa inhibitors on platelet activation and aggregation: implications for restenosis during percutaneous coronary intervention Heart, July 1, 2004; 90(7): 794 - 799. [Abstract] [Full Text] [PDF]

				E. N. Morgan, T. H. Pohlman, C. Vocelka, A. Farr, G. Lindley, W. Chandler, J. M. Griscavage-Ennis, and E. D. Verrier Nuclear factor {kappa}B mediates a procoagulant response in monocytes during extracorporeal circulation J. Thorac. Cardiovasc. Surg., January 1, 2003; 125(1): 165 - 171. [Abstract] [Full Text] [PDF]

				S. A. Leonard, A. Lydon, M. Walsh, C. Fleming, J. Boylan, and G. D. Shorten Does prior administration of enoxaparin influence the effects of levobupivacaine on blood clotting? Assessment using the Thrombelastograph(R) Br. J. Anaesth., June 1, 2001; 86(6): 808 - 813. [Abstract] [Full Text] [PDF]

				D. Dormann, K. J. Clemetson, and B. E. Kehrel The GPIb thrombin-binding site is essential for thrombin-induced platelet procoagulant activity Blood, October 1, 2000; 96(7): 2469 - 2478. [Abstract] [Full Text] [PDF]

				R. De Cristofaro, E. De Candia, S. Rutella, and J. I. Weitz The Asp272-Glu282 Region of Platelet Glycoprotein Ibalpha Interacts with the Heparin-binding Site of alpha -Thrombin and Protects the Enzyme from the Heparin-catalyzed Inhibition by Antithrombin III J. Biol. Chem., February 11, 2000; 275(6): 3887 - 3895. [Abstract] [Full Text] [PDF]

				C. Q. Li, A. Vindigni, J. E. Sadler, and M. R. Wardell Platelet Glycoprotein Ibalpha Binds to Thrombin Anion-binding Exosite II Inducing Allosteric Changes in the Activity of Thrombin J. Biol. Chem., February 23, 2001; 276(9): 6161 - 6168. [Abstract] [Full Text] [PDF]

				E. De Candia, S. W. Hall, S. Rutella, R. Landolfi, R. K. Andrews, and R. De Cristofaro Binding of Thrombin to Glycoprotein Ib Accelerates the Hydrolysis of Par-1 on Intact Platelets J. Biol. Chem., February 9, 2001; 276(7): 4692 - 4698. [Abstract] [Full Text] [PDF]