The Effects of Thromboxane Antagonism on the Transit Time of Platelets Through the Spleen

Summary

The spleen is well-known as a site for platelet pooling, although the mechanisms controlling intrasplenic platelet transit are essentially unknown. We tested the possibility that thromboxane A₂ might be involved in this control by measuring intrasplenic platelet transit time in 10 subjects receiving a specific thromboxane A₂ receptor antagonist (AH23848B; 70 mg; Glaxo Group Research Ltd), in 10 receiving aspirin (300 mg) plus dipyridamole (75 mg), and in 9 receiving placebo. All doses were administered 3 times daily commencing 4 days prior to transit time measurement.

Mean intrasplenic platelet transit time was measured by monitoring the kinetics of equilibration of ¹¹¹In radiolabelled platelets between blood and spleen following intravenous injection. There was no difference between the mean transit time in the 3 groups of subjects, lending no support to the hypothesis that thromboxane A₂ is involved in the control of platelet traffic through the spleen.

Keywords

Thromboxane - Spleen platelets - ¹¹¹Indium

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