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Thromb Haemost 1981; 45(03): 257-262
DOI: 10.1055/s-0038-1650183
Original Article
Schattauer GmbH Stuttgart

The Effect of the Phospholipase Inhibitor Mepacrine on Platelet Aggregation, the Platelet Release Reaction and Fibrinogen Binding to the Platelet Surface

P D Winocour
The Department of Pathology, McMaster University, Hamilton, Ontario, Canada
,
R L Kinlough-Rathbone
The Department of Pathology, McMaster University, Hamilton, Ontario, Canada
,
J F Mustard
The Department of Pathology, McMaster University, Hamilton, Ontario, Canada
› Author Affiliations
Further Information

Publication History

Received 27 May 1980

Accepted 21 April 1981

Publication Date:
06 July 2018 (online)

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Summary

We have examined whether inhibition by mepacrine of freeing of arachidonic acid from platelet phospholipids inhibits platelet aggregation to collagen, thrombin or ADP, and the release reaction induced by thrombin or collagen. Loss of arachidonic acid was monitored by measuring the amount of 14 C freed from platelets prelabelled with 14 C-arachidonic acid. Mepacrine inhibited 14 C loss by more than 80% but did not inhibit thrombin-induced platelet aggregation and had a small effect on release. ADP-induced platelet aggregation did not cause 14 C loss. Mepacrine inhibited ADP-induced platelet aggregation by inhibiting the association of fibrinogen with platelets during aggregation. The effect of mepacrine on fibrinogen binding could be considerably decreased by washing the platelets but the inhibition of 14 C loss persisted. Platelets pretreated with mepacrine and then washed show restoration of aggregation to collagen. Thus, mepacrine has two effects; 1. it inhibits phospholipases, 2. it inhibits fibrinogen binding. Freeing of arachidonic acid is not necessary for platelet aggregation or the release reaction.

Keywords

Platelets - Phospholipases - Mepacrine - Fibrinogen binding
 

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