Effect of aspirin on platelet 5-hydroxytryptamine and beta-thromboglobulin plasma levels in patients with myeloproliferative diseases.

14 patients with myeloproliferative diseases (MD) showed low 5-hydroxytryptamine (5-HT) platelet content and high beta-thromboglobulin (beta-TG) plasma levels. This pattern could support the view that MD platelets undergo "in vivo" degranulation. A single dose of aspirin was unable to induce modifications of platelet 5-HT and plasma beta-TG, whereas 6 out of 14 patients treated over 7 days period with the drug showed a decrease but not normalization in their beta-TG levels. No modification of platelet 5-HT was obtained suggesting that the cause of dense bodies deficiency may lie in the production of abnormal platelets and not be related to "in vivo" degranulation.