Inhibition of thromboxane and prostacyclin production in whole blood by adrenoceptor antagonists

There is increasing evidence implicating thromboxane A 2 (TxA 2 ) in vascular disease. Adrenergic blocking agents have been used with success in the secondary prevention of myocardial infarction. The aim of this study was to determine whether adrenergic blocking agents had any effect on the production of TxA 2 and prostacyclin (PGI 2 ) from whole blood in vitro. Fresh whole blood without anticoagulant was placed in glass tubes containing either drug or vehicle, the latter acting as control, and allowed to clot at 37°C for 30 minutes. The serum PGI 2 metabolites (PGI 2 M) and TxB 2 (the stable hydration product of TxA 2 ) were determined by radioimmunoassay. Labetalol, pindolol and propranolol all inhibited both PGI 2 M and TxB 2 production in a dose dependent manner, while atenolol had no effect. Labetalol was the most potent significantly inhibiting TxB 2 production at a drug concentration compatible with that found in-vivo . This inhibitory effect on TxB 2 production may be of benefit in the treatment of vascular disease.