Differences among beta-adrenoceptor blocking drugs in modifying platelet aggregation and arachidonic acid liberation under thrombin stimulation.

The dose-dependent inhibition of thrombin stimulated platelet aggregation due to beta-adrenoceptor blocking drugs followed the rank order of potency: propranolol greater than alprenolol greater than metipranolol and correlated with arachidonic acid (3H-AA) liberation. Atenolol which slightly potentiated stimulated aggregation increased also the liberation of 3H-AA from membrane phospholipids of isolated platelets. Stimulation of platelets resulted in decreased 3H-AA incorporation into phosphatidylcholine, phosphatidylinositol and phosphatidic acid and increased incorporation into phosphatidylethanolamine and phosphatidylserine. Alprenolol, metipranolol and propranolol enhanced the incorporation of 3H-AA into phosphatidylcholine of stimulated platelets.