Effect of propranolol, practolol and atenolol on human platelet thromboxane formation and plasma levels of prostaglandins 6-keto-F1 alpha and E2.

The effects of three different beta-adrenergic blocking drugs, propranolol, practolol and atenolol on platelet thromboxane production and the release of prostacyclin and prostaglandin E2 into the circulation were investigated in healthy volunteers. The beta-adrenergic antagonists were administered intravenously at equipotent doses. The serum TxB2 levels after whole blood clotting and the arterial and venous plasma concentrations of 6-keto-PGF1 alpha and PGE2 were measured before and during a 60 min period after the administration of the drugs, using radioimmunoassay. Practolol and atenolol elicited a significant decrease in platelet thromboxane formation but remained without effect on plasma 6-keto-PGF1 alpha and PGE2 levels. In contrast, propranolol did not influence serum TxB2 concentrations but induced a significant increase in plasma content of 6-keto-PGF1 alpha and PGE2. The results indicate that beta-adrenergic antagonists alter the balance between the proaggregatory, vasoconstricting and antiaggregatory, vasodilating prostanoids in the human cardiovascular system. Although the direction of the action of these drugs seems to differ depending on the selectivity of the beta-adrenoceptor blocking properties the net effect of this action should be beneficial.