Involvement of arachidonic acid and its metabolites in the inhibitory effect of beta-adrenoceptor blocking drugs on blood platelets.

: Propranolol (PRO), alprenolol (ALP), metipranolol (MET) and oxprenolol (OXP) inhibited arachidonic acid (AA) liberation from membrane phospholipids, malondialdehyde (MDA) formation and thromboxane B2 (TXB2) production in stimulated platelets. The inhibition was dose-dependent and with slight variations followed the rank order of potency: PRO greater than or equal to ALP greater than or equal to MET greater than or equal to OXP. Atenolol (ATE) was without any inhibitory effect. Inhibition of the arachidonic acid pathway in stimulated platelets may significantly contribute to the antiaggregatory effect of beta-adrenoceptor blocking drugs.