Ticlopidine Facilitates the Deaggregation of Human Platelets Aggregated by Thrombin

M Cattaneo; B Akkawat; R L Kinlough-Rathbone; M A Packham; C Cimminiello; P M Mannucci

doi:10.1055/s-0038-1642389

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 1994; 71(01): 091-094
DOI: 10.1055/s-0038-1642389

Review Article

Schattauer GmbH Stuttgart

Ticlopidine Facilitates the Deaggregation of Human Platelets Aggregated by Thrombin

Authors

M Cattaneo

The Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Institute of Internal Medicine, IRCCS Maggiore Hospital and University of Milano, Italy
B Akkawat

The Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Institute of Internal Medicine, IRCCS Maggiore Hospital and University of Milano, Italy
R L Kinlough-Rathbone

¹Department of Pathology, McMaster University, Hamilton, Ontario
M A Packham

²Department of Biochemistry, University of Toronto, Toronto, Ontario
C Cimminiello

³Medicina IV, San Carlo Hospital, Milano, Italy
P M Mannucci

The Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Institute of Internal Medicine, IRCCS Maggiore Hospital and University of Milano, Italy

Abstract

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Summary

Normal human platelets aggregated by thrombin undergo the release reaction and are not readily deaggregated by the combination of inhibitors hirudin, prostaglandin E₁ (PGE₁) and chymotrypsin. Released adenosine diphosphate (ADP) plays an important role in the stabilization of thrombin-induced human platelet aggregates. Since ticlopidine inhibits the platelet responses to ADP, we studied thrombin-induced aggregation and deaggregation of ¹⁴C-serotonin-labeled platelets from 12 patients with cardiovascular disease before and 7 days after the oral administration of ticlopidine, 250 mg b.i.d. Before and after ticlopidine, platelets stimulated with 1 U/ml thrombin aggregated, released about 80–90% ¹⁴C-serotinin and did not deaggregate spontaneously within 5 min from stimulation. Before ticlopidine, hirudin (5× the activity of thrombin) and PGE₁ (10 μmol/1) plus chymotrypsin (10 U/ml) or plasmin (0.06 U/ml), added at the peak of platelet aggregation, caused slight or no platelet deaggregation. After ticlopidine, the extent of platelet deaggregation caused by the same inhibitors was significantly greater than before ticlopidine. The addition of ADP (10 μmol/1) to platelet suspensions 5 s after thrombin did not prevent the deaggregation of ticlopidine-treated platelets. Thus, ticlopidine facilitates the deaggregation of thrombin-induced human platelet aggregates, most probably because it inhibits the effects of ADP on platelets.

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References

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