[Mechanism of the anti-aggregation action of thyroxine and insulin].

Thyroxine and insulin inhibit the aggregation capacity of platelets. To study the mechanisms of the antiaggregation action of thyroxine and insulin, platelets obtained from patients with diffuse toxic goiter and from rabbits with experimental hyperinsulinemia were incubated with acetylsalicylic acid and indomethacin. Acetylsalicylic acid or indomethacin were found to suppress the aggregation activity of thyrotoxicosis patients' platelets. Acetylsalicylic acid did not inhibit the aggregation activity of platelets of the rabbits pretreated with insulin. Based on the data obtained a hypothesis is advanced according to which thyroxine inhibits the platelet aggregation, interfering with the release of arachidonic acid from phospholipids of platelets (thrombocytopathy A), whereas insulin--by blocking the cyclooxygenase activity (thrombocytopathy B).