Exercise-Induced Increase in Plasma Arachidonic Acid and Thromboxane B2 in Healthy Men

Publisher Website
Google Scholar
Abstract
We examined the effects of β-blockade with the nonselective antagonist propranolol, the cardioselective antagonist atenolol, and the cardioselective antagonist with partial agonist activity, practolol, on the levels of free arachidonic acid (AA), thromboxane B2 (TxB2), prostaglandin (PG) E2, and 6-keto-PGF1α in plasma, and TxB2 production by platelets during clotting in six normal subjects during sub-maximal dynamic exercise. The drugs were given intravenously in equipotent increasing doses before the exercise test. Exercise induced a clear increase in AA, TxB2, and 6-keto-PGF1α in plasma. During the first 60 min of exercise all three β-blockers decreased the plasma levels of AA and TxB2. Propranolol (0.19 mg/kg) was slightly more effective than atenolol (0.19 mg/kg) or practolol (0.64 mg/kg); however, at exhaustion, propranolol was markedly more effective than the other two blockers. Plasma 6-keto-PGF1α and PGE2 levels were less affected by β-blockade during exercise, and no significant effect was seen on TxB2 formation by platelets. The plasma 6-keto-PGF1α/TxB2 ratio was markedly higher after propranolol treatment than after treatment with the other two blockers during the exercise period. These results suggest that the capability of a nonselective blocker to inhibit both β1- and β2-adrenergic receptors may be of advantage because of the more effective inhibition of thromboxane formation than with a cardioselective blocker, especially when the sympathetic tone is markedly increased.
Keywords