PAF-Acether May Not Mediate the Third Pathway of Platelet Aggregation since Self-Desensitization Reduces the Effects of Low Thrombin but Enhances Those of Convulxin

Françoise Wal; Danielle Joseph; Lhousseine Touqui; B Boris Vargaftig

doi:10.1055/s-0038-1661245

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 1985; 53(01): 099-104
DOI: 10.1055/s-0038-1661245

Original Article

Schattauer GmbH Stuttgart

PAF-Acether May Not Mediate the Third Pathway of Platelet Aggregation since Self-Desensitization Reduces the Effects of Low Thrombin but Enhances Those of Convulxin

Françoise Wal

The Unité des Venins, Département de Physiopathologie expérimentale. Institut Pasteur, Paris, France

,

Danielle Joseph

The Unité des Venins, Département de Physiopathologie expérimentale. Institut Pasteur, Paris, France

,

Lhousseine Touqui

The Unité des Venins, Département de Physiopathologie expérimentale. Institut Pasteur, Paris, France

,

B Boris Vargaftig

The Unité des Venins, Département de Physiopathologie expérimentale. Institut Pasteur, Paris, France

› Author Affiliations

Abstract

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Summary

PAF-acether (platelet-activating factor) was hypothesized as the mediator of the ADP and thromboxane-independent activation of platelets induced by thrombin (Thr) and by the snake venom glycoprotein convulxin (Cx). Aspirinized rabbit platelets self-desensitized to PAF-acether were less responsive to low amounts of Thr, as expected if PAF-acether would be formed, but were hyper-reactive to Cx, in contradiction with its hypothesized mediating role. Aggregation by higher concentrations of Thr overcame inhibition. Experiments with ADP-depleted platelets showed that secretion is neither involved with desensitization to PAF-acether nor with hyper-reactivity to Cx. Those effects required the presence of PAF-acether in the platelet suspension and persisted when transformation of PAF-acether into its recognized metabolite alkyl-acyl-glycerophosphorylcholine was inhibited. The ADP and thromboxane-independent activation of rabbit platelets by low and medium concentrations of Thr may be accounted for by platelet formation of PAF-acether, but overall the contrasting effects of platelet desensitization to PAF-acether on responsiveness to Thr and to Cx suggest that the third pathway of aggregation requires other explanations.

Key words

ADP - Convulxin - PAF-acether (platelet-activating factor) - Thromboxane - Thrombin - Rabbit platelets

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References

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