Platelet thromboxane synthesis and release reactions in myeloproliferative disorders.

A group of patients with myeloproliferative disorders was studies with respect to platelet aggregation responses, release of beta-thromboglobulin and incorporated 5-hydroxy-tryptamine, and synthesis of thromboxane b 2. In all patients the resting plasma beta-thrombo-globulin was elevated. Aggregation responses were frequently impaired to adrenaline, arachidonic acid, A23187 and the prostaglandin endoperoxide analogue, U44069. Both 5-hydroxy-tryptamine and beta-thromboglobulin release were greater with patients' platelets than with those of controls in response to adrenaline, ADP and U44069. The patients' platelets produced more thromboxane B2 than did controls, irrespective of the agonist used, yet those aggregating agents which are thought to act by generating thromboxane A2 were relatively ineffective in causing aggregation. This might reflect resistance to thromboxane A2 action in these patients, which is met by increased thromboxane formation.