Effects of short-term beta blockade on blood pressure, plasma thromboxane B2, and plasma and urinary prostaglandins E2 and F2 alpha in normal subjects.

The effect of short-term beta blockade with the nonselective antagonist propranolol and with the cardioselective antagonist metoprolol on arterial blood pressure, heart rate, serum renin activity, plasma thromboxane (Tx) B2 (the stable metabolite of TxA2). and plasma and urinary prostaglandin (PG) E2 and F2 alpha levels were examined in 11 normal subjects. After propranolol (160 mg by mouth), supine and standing mean arterial pressure (MAP) fell from 82 +/- 2 and 88 +/- 4 mm Hg to 71 +/- 3 (P less than 0.001) and 78 +/- 3 mm Hg (P less than 0.01) within 13 hr. MAP fell from 78 +/- 2 and 88 +/- 3 mm Hg to 72 +/- 2 (P less than 0.025) and 80 +/- 2 mm Hg (P less than 0.01) after metoprolol (200 mg by mouth). These blood pressure effects were associated with beta blockade; both drugs induced reduction in heart rate and serum renin activity and the reductions were of the same order. Propranolol and metoprolol also reduced plasma TxB2 levels by 33% (P less than 0.005) and 46% (P less than 0.05), but plasma and urinary PGE2 and PGF2 alpha levels were not changed by either drug. These findings suggest that changes in PGE2 or PGF2 alpha levels are unlikely to contribute to the short-term hypotensive effects of propranolol or metoprolol in normal subjects. Alterations in the synthesis or metabolism of the potent vasoconstrictor and proaggregatory drug TxA2, however, may be involved in the hypotensive, cardioprotective, and antiplatelet effects of beta-adrenergic antagonists.