β-adrenergic receptor blockade as a therapeutic approach for suppressing the renin-angiotensin-aldosterone system in normotensive and hypertensive subjects

Abstract

Although β-adrenergic–blocking drugs suppress the renin system (RAAS), plasma angiotensin II (Ang II) responses during β-blockade have not been defined. This study quantifies the effects of β-blockade on the RAAS and examines its impact on prorenin processing by measuring changes in the ratio of plasma renin activity (PRA) to total renin. In normotensive (N = 14) and hypertensive (N = 16) subjects, blood pressure (BP), heart rate, PRA, plasma prorenin, plasma total renin (prorenin + PRA), ratio of PRA to total renin (%PRA), plasma Ang II, and urinary aldosterone were measured before and after 1 week of β-blockade. Plasma renin activity, Ang II, and urinary aldosterone levels were similar for normotensive and hypertensive subjects. Plasma renin activity correlated with Ang II. Total renin, which is proportional to (pro)renin gene expression, was lower in hypertensive subjects and was inversely related to BP. β-Blockade decreased BP and heart rate in both groups, with medium- and high-renin hypertensive subjects responding more frequently than those with low renin. β-Blockade consistently suppressed PRA, Ang II, and aldosterone. Total renin was unchanged, thus, %PRA fell. These results indicate that β-blockers suppress plasma angiotensin II levels, in parallel with the marked reductions in PRA and urinary aldosterone levels in normotensive and hypertensive subjects. The suppression of Ang II levels was comparable to that produced during angiotensin converting enzyme (ACE) inhibition. However, by reducing prorenin processing to renin, β-blockers do not stimulate renin secretion, unlike ACE inhibitors and Ang II receptor antagonists. This unique action of β-blockers has important implications for the treatment of cardiovascular disease.