Altered intraplatelet arachidonic acid metabolism during the acute state of unstable angina

Thromboxane A2 (TxA2) generation and 1-14C arachidonic acid (AA) metabolism by platelets (stimulated with thrombin) were studied in vitro in 16 patients with unstable angina both during the acute and chronic inactive phase of the angina. Eight patients with stable effort angina and 21 controls were also investigated. In acute unstable angina 1-14C AA metabolism was significantly increased through cyclooxygenase pathway resulting in a higher selective TxA2 generation than in stable effort angina and in controls (p<0.01). No differences were found between patients with stable effort angina and controls. The alterations in AA metabolism were no longer found when patients reverted to the inactive phase of angina. TxA2 generation by platelets was independent of the number of the daily ischemic attacks (r=0.17, ns) in patients with unstable angina. Present results indicate that an altered intraplatelet AA metabolism leading to the increased TxA2 synthesis occurs simultaneously with the conversion of angina from the chronic to the acute phase.